Cleavage of Thick Seams in the Prokopyevsk District and Its Influence on Stoping Operations

I. A. Molchanov and A. A. Belitsky.

INTRODUCTION

In the mining of thick seams in the Prokopyevsk and Kiselevsk districts of Kuzbass, where some coal seams—such as the Moshchnyi Gorelyi, the III and IV Vnutrennie—reach 8–10 meters and even more in normal thickness, the carrying out of stoping operations has encountered a number of serious difficulties arising from the intense fracturing of the coals.

In connection with this, in 1938 the Scientific Research Institute of Kuzbassugol put forward a topic for the study of cleavage in the coals and enclosing rocks of the indicated districts of Kuzbass and its influence on stoping operations, with the aim of selecting the most rational system for mining thick seams. The execution of this topic was assigned to the Department of Prospecting of the Tomsk Industrial Institute.

In view of the novelty of the question and the absence of a developed methodology for studying cleavage, especially from the standpoint of the specific requirements of production, the execution of this work was planned for 2 years; for the first year the following tasks were set:

1. Study of cleavage planes in coal in stoping faces and partly in development workings, within the limits accessible for observation, in the seams—the Gorelyi and IV Vnutrennii of the Koksovaya mine in the Prokopyevsk district.

2. Division of cleavage planes into exogenous and endogenous ones, their relative manifestation, and their influence on coal breaking and on the stability of the face.

3. Tracing of the most important planes along the strike and dip of the mine field, compilation of a cleavage grid for the investigated areas, and study of its possible changes within the limits of the mine field.

4. Changes in the structure of the cleavage grid and in the character of manifestation of individual cracks when approaching lines of disturbance.

5. Study of the influence of cleavage cracks on the stability of the face, depending on the orientation of the face plane with respect to the cleavage.

1. Determining the influence of water penetrating from the upper horizons on the stability of the face under different orientations of the cleavage cracks.

The main objective of the first year of work was, in fact, to develop a methodology for observations and, especially, for processing the collected materials, with the expectation that the final results would be presented in a sufficiently simple and clear form, convenient for use by the appropriate specialists in solving purely operational problems.

In the course of the work we had to deviate somewhat from the planned program. In particular, item 6 was omitted entirely, since the working field of the Koksovaya mine down to the 215 m horizon, where all development and stoping operations are currently concentrated, is completely drained, and no inflow of water into the faces is observed. The only exception was an accidental breakthrough of water from a fire-water pipeline, which caused an accident in one of the stoping faces. But even in this case it was not possible to carry out the observations required by the program, because it was impossible to gain access to the face.

In addition, it turned out that at the Koksovaya mine the seams of interest to us in the 1st, 2nd, and 3rd wings of the folds have almost been worked out, while the 6th wing had not yet been laid out. Thus, all work, both in development and in coal extraction, is concentrated mainly in the 4th and partly in the 5th wings, where only two systems of stoping operations are used—“herringbone” and diagonal strips.

Therefore we somewhat broadened the front of our work, including in the program, in addition to the two seams mentioned above, also the III Inner seam, which here reaches 5–6 meters in thickness and is worked mainly by longwalls.

In addition, observations were carried out in the neighboring field of mines 3 and 3-bis, in two wings, on the Gorely, III and IV Inner seams, and partly on the Moshchny seam.

The inclusion in the observation program of work in the field of mines 3 and 3-bis also had other motives. Here, on one of the sections of the Gorely seam, there is an experimental site of the Kuzbassugol Research Institute, where experimental extraction of this thick seam was undertaken by three different systems—inclined strips, horizontal strips, and zones.

This site was of particular interest for our purpose, since three different systems, located practically in one place, made it possible to organize observations of the influence of one and the same cleavage pattern on differently oriented stoping faces. Unfortunately, we were unable to carry out these observations in full, since during our work extraction at the experimental site was conducted intermittently.

As the person responsible for the topic for the first year of the department’s work, Associate Professor A. A. Belitsky was appointed, while the immediate supervision of the execution of the work, especially at

At the first stage, when it was necessary to develop a methodology for observations and for processing the materials, the work was undertaken by the head of the department, Prof. I. A. Molchanov. As assistant observers, the department’s postgraduate student, engineer-geologist V. A. Monin, and graduating students K. V. Mironov and V. M. Lyapkin were brought into the work; they processed the material they had collected in their diploma projects.

The present work was written jointly by I. A. Molchanov and A. A. Belitskii. The former wrote the general part, the methodology of observations and processing of the materials, the analysis of the cleavage lattice, and, jointly with A. A. Belitskii, the conclusion. The latter compiled the description of observations in the faces, since all the work of collecting the primary factual material was carried out with his participation and under his personal supervision and direction, as I. A. Molchanov, owing to illness, was unable to take direct part in this work.

GENERAL PART

1. The Present State of the Study of Cleavage and the Basic Terminology

The study of cleavage is not a new question. In almost every manual on coal deposits, questions concerning the manifestation of cleavage and its influence on coal breaking are touched upon to one degree or another. In the mining-engineering literature there are also quite a few articles dealing with this question. But there are, in general, very few special works on the study of cleavage, and apparently none at all that would treat this question not from the standpoint of facilitating coal breaking, but in the sense of the stability of the face and the safety of conducting extraction work in the mining of thick coal seams.

In our Union, the systematic study of cleavage is being carried out by the engineer-geologist G. A. Ivanov. His work, “Jointing (cleavage) in the coals and accompanying rocks of the Donets and Moscow Basins, its origin and use in Stakhanovite methods of work” (4), is a very important and interesting work, laying the foundation for investigations of this kind. Unfortunately, his later works, including the work on the study of cleavage in Kuzbass and, in particular, even in the Prokopyevsk district, have not yet been published, and therefore we could not make use of their results.

Especially valuable in the named work, from our point of view, is the rather complete survey of the Russian and foreign literature on cleavage; the clarification of the concepts—cleavage and jointing—since previously different meanings had been assigned to them; the classification of cleavage planes and their diagnostic features; and also the instructions and practical directions on the methodology of field observations. As for the general conclusions at which the author arrives as a result of his work, they are reduced mainly to questions of the regional tectonics of the areas he investigated and have no direct bearing on our topic. The production conclusions, however, are very brief and consist of general phrases about the importance of studying cleavage for the proper orientation of workings, and of repeating the well-known proposition that orienting the face parallel to the cleavage plane facilitates coal breaking.

At the beginning of 1938, the geologist of the Koksovaya mine, V. A. Azimov (1), studied cleavage and its influence on extraction work in the thick seams of that mine.

This work coincided entirely with our topic. It contains many very interesting observations of stoping faces, which the author was able to carry out systematically over several months, as well as valuable practical conclusions. Unfortunately, during our work all of V. A. Azimov’s materials were still being processed, and we were able to familiarize ourselves with them only just before the completion of our work at the mine. However, we were able to make use, already in the course of the work, of certain advice and indications drawn from personal conversations with the author, for which we consider it our duty to express our gratitude to Comrade Azimov.

The other literary sources with which we had occasion to become acquainted in the course of preparing and carrying out our work did not have any substantial influence on it. A list of them is placed at the end of the article, and references are made in the exposition of the corresponding parts of the text.

In presenting the material we adhere to the terminology proposed by G. A. Ivanov. The latter, in agreement with Yu. A. Zhemchuzhnikov, holds that the term separateness should be understood as the tendency of coal or rock to split along definite directions. This ability or tendency is conditioned by a system of visible or hidden cracks formed in the rock for various reasons. The aggregate or combinations of several surfaces of separateness determine the shape of the pieces into which these rocks divide under their influence. This, then, will be the form of separateness—cubic, parallelepipedal, columnar, slabby, and so forth. By the term cleavage, however, he understands the very phenomenon of regular fissuring of coals and rocks, conditioned by those same various causes.

According to the genetic criterion, all these cracks may be divided into the following three groups.

The first group includes cracks conditioned by causes of an endogenous order, dependent on internal physical and chemical alteration of the substance of the coal or rock. They arise as a result of a reduction in the volume of the primary original mass during its dehydration and internal molecular regroupings under the influence of diagenesis and coalification, without any noticeable participation of external mechanical effects. In agreement with G. A. Ivanov, we shall call these cracks endogenous cracks.

The second group of cracks arises under the influence of external mechanical effects from stresses that occur in a deforming seam during dislocations of the coal-bearing strata. This will be the exogenous group of cracks, conditioned chiefly by tectonic causes.

Finally, a third group should be distinguished—according to the studies of Hetté (5), Ende (8), and also Faulkner and Phillips (9)—comprising cracks that arise in coal seams under

under the influence of their working. According to Ende, it would be convenient to call this group of cracks pressure cracks (Drucklager), or accidental, exotic cracks, as being caused by an accidental cause—the disturbance of the equilibrium of the rocks during the driving of stoping or development workings.

The latter group of cracks does not properly belong to cleavage, since it is not connected with definite regularities in the conditions of occurrence of the seam and is caused not by natural causes, but by the artificial weakening of the resistance of coal to crushing, as a result of its partial extraction. But for us the conditions under which these cracks form are of essential importance. In cases where their direction coincides with, or is close to, the direction of some system of cracks of natural cleavage, the degree of manifestation of this system will be considerably intensified in comparison with the others. In the opposite case they obscure the manifestation of cleavage cracks, make their identification difficult, and may lead to false conclusions. Therefore the possibility of the occurrence of these cracks, especially in stoping faces when thick seams are being worked, must always be taken into account.

2. Diagnostic features of cracks of various origins.

A. Endogenous cracks.

Endogenous cleavage develops as a result of shrinkage of the rock mass, due to its compaction and diagenesis. In this process there are usually formed three mutually perpendicular and conjugate systems of cracks. One of them coincides with the plane of bedding, while the other two are situated normal to the first and mutually perpendicular to one another. The reason for this regularity in the orientation of the latter two planes has not yet been precisely established. Apparently, their direction depends on the primary planar extent of the seam, and perhaps of the entire coal-bearing series. One of these systems is usually expressed more distinctly and is called the main one; the second, less distinctly expressed, is called the butt one.

Endogenous cleavage affects not only coals, but also the enclosing rocks, especially sandstones; moreover, in sandstones these cracks sometimes appear very distinctly. However, even in cases of pronounced manifestation of cleavage cracks in rocks, these cracks are arranged in a comparatively sparse network, with distances between them measured in tens of centimeters. In rocks homogeneous in composition—clayey shales and uniform-grained sandstones—endogenous cleavage is, in general, expressed more distinctly than in heterogeneous thin-bedded rocks consisting of alternating interbeds of sandy and clayey material.

Unlike the enclosing rocks, the contraction of a coal seam proceeds more energetically, since in this case diagenesis consists in complex chemical transformations of the original mass during its coalification, associated with a large loss of material in the form of volatile components released from it; whereas in the enclosing rocks—sands and clays—this process is expressed in simple dehydration and compaction. Owing to this, endogenous cleavage in coals is manifested more intensively—in the form of a very dense system of cracks, the distances between which are measured in centimeters and even fractions of centimeters.

The chief distinguishing features of endogenous cracks are the following:

1. The surfaces of endogenous cracks are always normal, or nearly normal, to the bedding surface, and therefore the lines of their intersection are almost perpendicular to the roof and floor of the seam.

2. Both endogenous planes are mutually conjugate and almost perpendicular to one another. Therefore, having noticed one, it is easy to find the other as well.

3. The principal plane is usually expressed more distinctly, as compared with the end plane, and is therefore found more easily. In the face and on pieces of broken coal it forms large, even and smooth faces, without traces of rubbing. Sometimes infiltration inclusions of calcite, gypsum, or pyrite are observed along it.¹ In places, fracturing along the principal plane is manifested so intensely that the entire coal seam appears to consist of thin plates several millimeters thick, oriented parallel to this plane. At times such cleavage completely masks the stratification.

4. The end plane is usually expressed considerably more weakly, both in terms of crack density and in the vividness of their manifestation. In the face and on broken pieces of coal it appears as small faces cutting, at a right angle, the projections of plates that break off along the principal plane.

Sometimes, apparently in those cases when tectonic stresses have caused fracturing of the coal in a direction close to that of the end plane, the latter appears more sharply and in places becomes predominant. But in such cases striation and polish (slickensides), and other attributes characteristic of exogenous cracks, usually appear on it as well, and the endogenous plane essentially becomes transformed into an exogenous one.

However, when tracing endo-cleavage cracks over large areas, changes are sometimes noticed in the degree of their manifestation independently of the influence of tectonic effects; moreover, these changes may reach such limits,

¹ In the Prokopyevsk district we have not had occasion to observe such inclusions.

that the end plane will prove to be more distinctly expressed than the main one. In other words, the two planes under consideration will exchange places. The reasons for such changes have not yet been clarified. It is possible that they depend on the proximity of the point of observation to the natural boundaries of the seam or basin.

B. Exogenous cracks.

Exogenous cleavage develops under the influence of tectonic causes. Cracks are formed as a result of shearing stresses arising during compression of the coal-bearing strata. Their orientation is determined by the direction of the compressive forces and, in general, does not depend on the conditions of occurrence of the seam.

However, according to our observations, in thick dislocated seams one system of exogenous cracks usually coincides, or nearly coincides, with the bedding surfaces of the coal, thereby sharply emphasizing the latter.

The most important distinguishing features of exogenous cracks are the following.

1. An arbitrary position with respect to the elements of the seam’s occurrence. The only exception is one system of exogenous cracks which, as indicated above, is usually confined to the bedding planes, being caused by interbedded slipping of individual bands of coal during bending of the seams. In thick seams such interbedded displacements attain considerable dimensions and are accompanied by the formation, within the seam, of powdery partings (sal’niki), and sometimes of entire bands of soft coal (podkalochnik) with a thickness of up to 0.35 and even 0.80 m.

2. The surfaces of fractures along exogenous cracks are surfaces of more or less noticeable displacements, and therefore always bear traces of abrasion. In places they are smooth polished surfaces—slickensides—while in other cases they are ribbed, striated, sometimes more or less strongly curved, and far from always strictly parallel to one another. Mutual intersection or crossing of a system of such surfaces of one general direction often gives rise to the so-called comb-like separateness of the coal.

C. Pressure cracks.

These cracks are formed under the influence of the pressure of the overlying rocks above the mined-out space.

The English investigators Falkner and Phillips (9), who studied the conditions of formation and the character of such cracks, arrived at the following conclusions.

1. Pressure cracks ¹ are formed near development and stoping faces.

¹ The cited authors call these cracks “induced cleavage.”

1. The general orientation of these cracks is parallel to the face breast.

2. When the direction of the face plane changes, the direction of the cracks also changes; the latter curve, bending around the projections of the face and following the direction of its walls.

3. In narrow workings—furnaces, drifts, etc.—the cracks in the roof curve in the direction of movement of the face, and the narrower the working, the greater the radius of curvature.

4. The deviation of the plane of pressure cracks from the normal to the seam usually occurs toward the worked-out space and reaches up to 12°.

5. No definite dependence of pressure cracks on natural cleavage has been observed anywhere. Pressure cracks usually intersect the cleavage planes.

6. In the enclosing rocks, pressure cracks form more readily in clay shales than in sandstones. At depths down to 100 m from the surface, pressure cracks appear very rarely, even with a weak roof. At depths from 100 to 180 m they appear in a shale roof only in isolated cases, while at workings deeper than 180 m they always appear. In sandstones, pressure cracks appear only from a depth of 550 m, and from a depth of 700 m they are always observed.

The appearance of pressure cracks complicates observations of cleavage, especially when their direction is close to one of the directions of the latter, since cracks of the one and the other origin can easily be confused with each other.

The most important distinguishing features of pressure cracks as compared with cleavage cracks are the following.

1. The orientation of the cracks is parallel to the plane of the face or to the walls of the working.

2. Pressure cracks are always dull—without traces of slickensiding—and even—without striated surfaces.

3. The walls of pressure cracks passing through coal are often covered with coal dust.

3. Specific features of the geological setting of the district.

In the Prokopyevsk district, where our work was carried out, we had to deal with coal seams exceptional in thickness, namely: the III Internal seam, 5–6 m of normal thickness; the IV Internal seam—from 7 to 9.5 m; the Gorely seam, whose thickness ranges from 8–9 m; and the Moshchny seam, in which it reaches 14 m.

Kuzbass, as is well known, is characterized by sharp and strong disturbances of the productive series, owing to the intense pressures to which the coal-bearing sediments of the Kuznetsk Basin were subjected, mainly from the side of the Salair Ridge. The Prokopyevsk and neighboring Kiselevsk districts are located on the SW boundary of the basin, in immediate proximity to

the foothills of the Salair. It is therefore quite understandable that the coal-bearing series here was subjected to especially strong dislocations. The coal seams are gathered into numerous and steep NW folds, close to meridional in strike, and are complicated by a mass of disjunctives. The main tectonic fractures are situated, approximately, parallel to the axes of the folds and have a steep dip of 60–70° to the SE, toward the Salair. The secondary fractures branch off from them at various angles, cutting the limbs of the folds diagonally and across their strike.

It is interesting, incidentally, to note that the prevailing form of the main disjunctives is that of reverse strike-slip faults, affecting chiefly the NW limbs of anticlinal folds. The displacement of masses in this case occurred in such a way that each successive block, counting from NW to SE, was raised relative to the preceding one, being thrust over or upthrown onto the latter, and was shifted relative to it toward the southeast; the amplitudes of the actual relative displacements of adjacent blocks reach the order of several hundred meters.

It is also clear that under such conditions the comparatively brittle coal seams, enclosed in plastic enclosing rocks, among which argillites predominate, could not preserve the continuity of the coal substance composing them. It proved to be broken by numerous fractures, partly coinciding, or nearly coinciding, with the bedding planes (more precisely, surfaces), and partly cutting them at certain more or less considerable angles. This must, of course, have been especially sharply expressed in the thick seams, where the stresses during bending and shearing, other things being equal, reached maximum values.

Indeed, in the thick seams we observe a complex cleavage lattice. The whole seam, or some of the coal benches composing it, turn out to be intensely broken by fractures of various directions; moreover, the walls of almost all the fractures bear more or less vivid traces of slickensiding, indicating displacements of individual pieces of coal relative to one another. Thus here the basic distinction between endogenous and exogenous fractures is often completely obliterated, since every fracture served as a plane of slip during intraseam displacements.

It is interesting that the strongest displacements occurred along planes very close to the bedding planes. Sometimes these fractures coincide completely with the bedding planes; sometimes they deviate from them by certain very small angles, obscuring and masking the actual conditions of occurrence of the seam.

Less intense, but quite distinct, displacements also took place along the principal plane, whose strike is close to the strike of the seams. Thanks to crumpling and slickensiding

at the edges during displacements, this plane sometimes undergoes rather substantial deformations and deviations from its normal position in the seam. It undergoes especially strong deformations in the locks of folds, where, owing to bending of the seam, the conditions of its occurrence change (a reversal of the dip direction to the opposite one).

The end plane is, on the whole, preserved much better, probably because of its particularly favorable position—almost vertical and almost across the strike of the seams. Owing to this, it maintains its direction on both limbs of the folds. But on it, too, traces of rubbing and striation are observed in places, indicating micro-displacements.

As for the exogenous planes, they are rather numerous. The conditions of their occurrence vary within broader limits, which greatly hampers their separation and identification. Sometimes their direction approaches that of one of the endogenous planes, and then it is rather difficult to distinguish one system from another.

All this, taken together, greatly complicated the observations for studying the cleavage lattice and the regularities of its variation over the area of the investigated sectors.

Still greater difficulties were encountered in determining the “degree of manifestation” of cleavage cracks. It should be noted that, in general, there are no objective criteria for determining the degree of manifestation. It is determined by eye (more precisely, by muscular sense), i.e., by the relative ease with which the coal splits in one direction or another. Meanwhile, observations at two adjacent points, one of which is located in development workings and the other in a stoping face, often give incommensurable results.

The enormous cavities formed in the mining of thick seams, sometimes moreover rather carelessly stowed, cause strong roof pressure at the stoping faces, leading to the splitting of the coal. The blasting operations used almost everywhere further intensify this effect. In this case, splitting occurs predominantly along planes close to those along which the stresses arising in the coal tend to be released. And these, as is known from the laws governing the formation of pressure cracks, will chiefly be planes parallel to the face line. Hence it is understandable that in stoping faces, depending on their spatial orientation, only certain cleavage planes are emphasized at the expense of the others, although in pillars not affected by stoping operations the latter may be expressed no worse.

All these circumstances, which became apparent gradually in the course of the work, could not but affect its productivity, especially at the beginning. Observations at some points had to be repeated several times, comparing and correcting the results of observations in stoping and development workings.

This could not but affect the working method, which had to be modified several times in the course of carrying out the work, and partly also its results. Therefore the conclusions that we permit ourselves to draw from the data we obtained should be regarded as preliminary, deserving further refinement and verification.

4. Methodology of observations and processing of materials.

A. Methodology of observations.

In making the observations we adhered, in general, to the instructions proposed by G. A. Ivanov. We devoted special attention only to stoping workings, first, because the manifestation of cleavage cracks in the large exposures of stoping faces is most distinct, and, second, because only here did we have the opportunity to observe the direct influence of one or another system of cracks on the stability of the face and the roof of the workings. We considered it especially important to make observations in stoping workings along one and the same seam under conditions of different face orientation. Circumstances favorable to this were such systems of workings as diagonal slices and the “herringbone” system within seam IV of the Inner mine of the Koksovaya mine and the experimental section of the Gorelyi seam at mines 3 and 3-bis.

The conditions of occurrence of the cleavage planes were subjected to numerous measurements, with their mean values being established for each section of the seam, as well as the amplitudes of their deviations.

The detection of cleavage cracks in stoping faces presents no special difficulties. In the process of coal breaking, and especially immediately after blasting, all these cracks show up quite distinctly. Here it is important only to establish the degree of their manifestation independently of the orientation of the face and other causes of an accidental character, and also their influence on the stability of the walls and roof.

Much more difficult is the detection of planes in development workings, especially in the preserved faces of drifts and the walls of crosscuts. Here one has to do a good deal of work with a pick in order to reveal all those planes that were observed in the neighboring stoping face; moreover, the possibility of missing some of them is not excluded. However, endogenous planes are easily recognized here as well, owing to their characteristic orientation relative to the plane of the seam. The situation is usually more complicated with the detection of exogenous planes and their identification, because of the bends they undergo and significant deviations from their mean direction. The actual measurements of the attitude of the planes are elementary and are made with a mining compass; usually the azimuth and dip angle are recorded.

Rough notes in the face were kept in a notebook, where indi—

was recorded: 1) the place of observation and the character of the working; 2) all measurements of azimuths and dip angles, successively for each observed plane; 3) the intensity of cleavage in the sense of the density (frequency) of the occurrence of cracks; 4) the degree of manifestation, i.e., the ease with which the coal splits off (separates) in the given direction; 5) the character of the crack surfaces—bends, the presence of traces of rubbing, striations (measurement of the direction of striation); 6) the conditions of occurrence of the seam; and 7) the orientation of the plane of exposure. At the same time, a sketch of the face was made, indicating the position of the most important cracks and bedding, and typical specimens of partings were also taken, with an indication of their spatial orientation. In the case of a stoping face, notes were added concerning the splitting-off of the coal, with an indication of the cracks along which it occurs, the form and dimensions of the pieces that fall out, etc.

All observations made in one stoping face or in a development working, chiefly in a crosscut or at the end face of a drift, are considered as belonging to one point. Since the conditions of occurrence of the seam and the character of the cleavage lattice change in space comparatively slowly and gradually, the density of the points adopted by us, with intervals of 100–150 m, may be considered quite sufficient. However, our observation points are usually somewhat more closely spaced. This was caused not so much by a desire for more careful tracking of changes in the cleavage lattice as by other reasons—either by the convergence of stoping faces, or by the need to compare the behavior of planes in development and stoping workings.

All stoping and development operations, both at the Koksovaya mine and at mines 3 and 3-bis, are concentrated on one working level, between absolute elevations of 265 and 215 m. Therefore, all our observations practically belong to one horizon and can serve for deriving the variability of the cleavage lattice only along the strike.

For each observation point, a special card was compiled according to the form we had developed (Fig. 1), onto which the measurements and sketches made directly in the face were transferred.

B. Method of Processing the Materials.

The processing of the primary observations consisted of the following:

1. All observation points were plotted on the seam map of the working horizon in the form of a circle with the No. of the corresponding point; moreover, points located very close to one another were sometimes combined. We chose the map scale as 1:5000, since this comparatively small-scale map is more convenient for review, and on it the general structure of the deposit is more clearly delineated.

2. For each observation point, the mean values of the angles characterizing the conditions of occurrence of each plane were calculated.

1. To characterize changes in the cleavage lattice along the strike of a seam and in passing from one seam to another, all data from the average measurements at the points are presented in summary tables by seams, in which the points are arranged in the order of their spatial position.

2. For a clearer and more visual representation of the mutual disposition of the cleavage planes and of their relationships with the bedding plane, stereograms are constructed for all these planes, both for each observation point separately and as summaries for each sector (wing) of the seam as a whole. In addition to making clear the spatial arrangement of the observed planes, stereograms also make it possible to solve easily and quickly a whole series of geometric questions connected with them.

3. However, at times this is still insufficient. To solve certain production questions, especially questions connected with the spalling of coal in faces and the stability of their walls, depending not only on the orientation of the face plane but also on the direction of its advance, it is necessary to resort to the construction of block diagrams and even block models. We therefore also constructed block models.

Of all the possible methods for representing the conditions of occurrence of cleavage planes, we adopted the method of stereographic projections. This method, widely used in exact methods of petrographic investigation and sufficiently well known to every geologist, consists in general of the following.

A sphere of arbitrary radius is taken as the basis for projection. All lines and planes, arbitrarily oriented in space, are conceived as passing through its center \(O\) (Fig. 2). The lines of intersection of the planes with the sphere and the points of intersection of the lines with it are projected onto the equatorial plane of the sphere \(EH\), which at the same time is also the plane of the horizon. The projection used is not orthogonal but conical, one of the poles of the sphere being taken as the center of projection. Usually only the upper hemisphere \(EZH\), situated above the plane of the horizon, is considered, while the lower pole \(Na\) is taken as the center of projection.

It is clear that in this case the projections of all points of the upper hemisphere will not extend beyond the equatorial circumference, but will be located within this circle, called the circle of projection. If we divide the meridian arc \(EZ\) (Fig. 2) into equal intervals of \(15^\circ\) and join the points of division \((a, b, c, d, e)\) to the center of projection \(Na\), then at the points of intersection \((a', b', c', d', e')\) of these rays with the equator \(EH\) we obtain the projections of the division points onto the drawing plane. If now, through the points of division of the sphere \((a, b, c, d, e)\), we pass a series of horizontal planes, then the lines of section of the sphere by these planes (parallel circles) will be projected onto the drawing plane in the form of a series of concentric circumferences with radii \(Oa'\), \(Ob'\), \(Oc'\), etc.

Stereographic projections have the following interesting and valuable properties.

1. Any plane section of the sphere is projected onto the picture plane in the form of the circumference of a circle.

2. All angles drawn on the surface of the sphere are projected onto the picture plane without distortion.

The first property makes it possible to construct easily and quickly the stereographic projection of any plane from the elements of its occurrence. Suppose, for example, that some plane is specified by the azimuth of dip \(a\) and the dip angle \(\delta\) (Fig. 3).

Taking a circle of arbitrary radius (the circle of projection), we draw in it the direction of the meridian \(NS\). Then, from the center \(O\), we draw the ray \(OC_1\) in the direction of dip of the given plane and, perpendicular to it, the diameter \(A_1B_1\). The latter will obviously be the strike line of our plane. At one of the ends of this diameter, for example at point \(A_1\), we construct the angle \(\delta\), equal to the dip angle of the plane, and extend the line \(A_1C_1\) until it intersects the ray \(OC_1\) at point \(C_1\). Finally, from point \(C_1\) as center, we describe the arc \(A_1KB_1\), which will be the required projection of the given plane. In exactly the same way one can also construct any other plane, for example \(A_2KB_2\), while the line \(KO\) will obviously be the line of their mutual intersection (crossing).

This is done even more simply with the aid of a special stereographic net (Fig. 4). For this purpose the procedure is as follows. The tracing paper is superposed on the stereographic net (Fig. 4). The circle of projection is drawn on it, and the ends of the meridian \(0—180\) are marked. Then, without lifting the tracing paper, a point corresponding to the azimuth of dip of the plane that is to be represented is marked on the circumference of the circle of projection. After this, rotating the tracing paper about the center of the circle, the marked point is brought into coincidence with point 9 (the \(90^\circ\) point of the azimuthal circle), and the diameter \(0—180\) is drawn. This line, perpendicular to the line of dip of our plane, will represent its strike. In the left part of the net a series of arcs has been drawn resting on the diameter \(0—180\); these represent a series of planes inclined at various angles to the horizon, with intervals of dip angle of \(5^\circ\). From among them we choose the arc that corresponds to the dip angle of our plane and copy it onto the tracing paper. This arc will be the stereographic projection of our plane. In this way any plane, arbitrarily oriented in space, can be represented easily and quickly. Such a representation is elegant, precise, and graphic. It makes it possible not only to understand quickly the mutual relations of all the planes under consideration, but also to measure any geometrical elements formed by them; moreover, all such measurements are made easily and quickly with the aid of the same stereographic net.

Thus, with the aid of this net one can quickly and accurately measure the angles between the lines of intersection of planes, for example, the traces of cleavage planes on the plane of a seam or of a stope.

Let, for example, the plane \(A_1B_1\) (Fig. 3) be the plane of the seam, and the plane \(A_2B_2\) some cleavage plane, and suppose it is required to measure the angle \(KOB_1\), formed by the line of intersection \(KO\) with the strike line of the seam \(A_1B_1\), reckoned from the positive direction of the latter.

For this purpose we place the wax tracing, on which the indicated planes have been drawn, on the stereographic net so that the strike line of the seam \(A_1B_1\) coincides with the initial diameter of the net \(0—180\), and the point \(B_1\) coincides with \(0^\circ\). Then the arc \(B_1KA_1\), representing the plane of the seam, coincides with one of the arcs resting on the initial diameter (or passes between them). These arcs, resembling meridians on a globe, are divided by the corresponding net of parallels into intervals of \(5^\circ\), which makes it possible, along the corresponding meridian, easily to count off the number of degrees of the arc on which the central angle \(B_1OK\) rests.

Such measurements of linear angles between the traces of cleavage planes on some chosen plane are absolutely necessary for constructing block diagrams and block models. But sometimes it is also necessary to measure the dihedral angles between planes.

Since the dihedral angles between two planes are equal to the corresponding spherical angles at the point of intersection of the traces of these planes on the sphere, and since the latter are projected onto the picture plane without distortion, a rough idea of the magnitude of these angles is obtained by directly inspecting the stereogram (Fig. 3, and also Figs. 7, 8, 9, 10, 11, and 12¹). For a more accurate measurement of these angles one may use the same net (Fig. 4). Let, for example, it be required to measure the dihedral angle between the planes \(A_1B_1\) and \(A_2B_2\) (Fig. 3), given in the form of their stereographic projections. Noting that the dihedral angles between the planes of meridians are measured by an arc of the equator, we shall take point \(K\) as the pole; then the arcs \(KB_1\) and \(KB_2\) will be arcs of the corresponding meridians, as arcs of great circles passing through the point \(K\), which we have taken as the pole. The problem, consequently, reduces to finding the central plane perpendicular to the line of intersection of the given planes \(KO\), which will be the equatorial plane of our system, and to measuring the arc of this equator between the meridians.

This is most simply done as follows.

The stereogram of the seams, drawn on the wax tracing at the scale of the net, is superposed on the stereographic net so that the projection circles coincide, and the line of intersection of the planes \(KO\) coincides with the direction of the radius \(ZE\) of the net. Now imagine a vertical plane passing through the center of the sphere and the point \(K\). The projection of this plane on the stereogram will be expressed by the straight line \(KM\), passing through the center \(O\), and will be one of the meridians of our system. With the superposition indicated above, this plane

coincides with the equatorial section of the sphere EZW, and point M of the stereogram coincides with point W of the net. The arc EZW of the net is divided by concentric circles into 5° intervals. Measuring along these divisions, from point K in the direction toward M, an arc of 90°, we find a point lying on the equator of our system; and the arc passing through this point and resting on the diameter NS will be the required equator. It now remains only to measure the arc of this equator enclosed between the arcs of the meridians KB₁ and KA₂.

The method we have chosen for documenting observations and processing materials, and especially the use of stereographic projections for this purpose, undoubtedly represents a considerable step forward in the study of cleavage in coal deposits. At the same time, we cannot fail to note certain rather substantial shortcomings in our work.

The first methodological shortcoming is that we have not been able to develop objective criteria for determining the degree of manifestation of cleavage cracks, either in absolute or in relative terms. This must be made a task of future research.

The second shortcoming is that, having concentrated all our work on studying cleavage in thick seams, in accordance with the task assigned to us, we did not devote proper attention to studying it in adjacent, thinner seams. Because of this we are deprived of the possibility of giving a comparative analysis of the manifestation of cleavage in seams of different thickness. True, this question was not provided for by the theme of our work and arose only in the course of processing the material, when the field observations had already been completed. But it is unquestionably of great practical significance. We believe that in further work the study of cleavage should begin in seams of normal thickness, where its manifestation should be more regular. Only after the general regularities in the arrangement of cleavage cracks have been established may one proceed to study them in thick seams, where they undergo more or less substantial deviations from the norm owing to the specific character of deformation in thick seams and the additional stresses arising in them.

Analysis of the Cleavage Grid of the Field of the Koksovaya Mine and Mines 3 and 3-bis of the Prokopyevsk District

As already indicated above, a large part of our observations is confined to the 4th and 5th wings of the field of the Koksovaya mine (Fig. 5), or, in other words, to the western and eastern wings of the Small Anticline, and only a comparatively small part of them pertains to the field of mines 3 and 3-bis (Fig. 6). Observations in both cases were made both in stoping faces and in development workings in seams IV and III Vnutrennii and Gorelyi. In the field of mines 3 and 3-bis, in addition to these same seams, isolated observations were also made in the Moshchnyi seam.

The results of the observations are presented in summary tables by seams and districts, in the order of the spatial arrangement of the observation points; points located close to one another have been combined (see Tables 1–4, given at the end). From consideration of these tables the following conclusions may be drawn.

The seam richest in cleavage planes is seam IV Inner. Here, in addition to three endogenous planes, another 5 and 6 exogenous ones are observed, manifested to one degree or another. It should be noted that all these planes are also partly observed, in various combinations, in all the other seams we investigated. Thus their abundance here should be explained not only by features of the seam structure, but also by the fact that this seam was traced by us over a considerably greater extent than all the other seams, and moreover on both sides of the fold (through the saddle). In addition, the mining systems located here are precisely those most favorable for identifying cleavage planes—diagonal layers, a single-slope face, and herringbone. Almost all the cleavage planes observed in this seam bear slickenside traces, indicating more or less significant intra-seam displacements of coal fragments cleaved along the cleavage, so that the seam, generally speaking, no longer represents something whole, but is an agglomerate of these fragments.

Therefore, as the basis for analyzing the cleavage lattice we take the data obtained in studying seam IV Inner of the Koksovaya mine, supplementing them with all the other observations; we shall begin the review from the south of district 4.

A. Endogenous planes.

1. Bedding-plane cleavage.

One of the endogenous planes coincides, or almost coincides, with bedding-plane cleavage. In the southern part of district 4, in seam IV Inner, the azimuth of its dip ranges within 250–260°, and the angle is about 60°, generally coinciding with the elements of occurrence of the seam. However, in places some deviations of this plane are observed, both in the direction of dip, reaching 20 and even 30° (toward decreasing azimuths), and in the dip angles toward flattening. These deviations, together with slickenside traces on the bedding-plane cleavage surfaces, show that in the present case there is a superposition of two cleavage planes: one—endogenous, coinciding with bedding-plane cleavage, and the other—exogenous, having very similar elements of occurrence. In places this plane, dipping to the southwest: 223–230 at an angle of 35–47°, can be distinguished as an independent cleavage plane Exo—IV, but in the overwhelming majority of cases it is so closely connected by gradual transitions with bedding-plane cleavage that separating them becomes impossible. Therefore, it is usually not distinguished by us—

…which, naturally, could not fail to be reflected in the mean elements of the occurrence of the bedding plane, which, in this way, does not fully coincide with the actual occurrence of the seam. However, these deviations are generally so insignificant that they can have no practical importance.

In the northern part of the limb, as it approaches the hinge of the fold, the dip azimuth of this plane undergoes certain fluctuations caused by the presence of small additional bends and of one fairly large diagonal disturbance dipping to NW: 295–300° at an angle of 55° (in plan). Therefore, the mean dip azimuth remains almost unchanged, while the angle flattens somewhat.

Beyond the hinge of the fold, in the 5th limb, the direction of dip naturally changes almost to the opposite—from 255 to 55°, while the angle becomes steeper.

The endogenous bedding plane, emphasized by layer-parallel movements and by an additional exogenous plane (Exo—IV) partially coinciding with it, is everywhere expressed very distinctly and plays a very important role in the splitting of coal at the faces.

The principal plane, being conjugate with the bedding, behaves in general analogously, although it fluctuates within somewhat wider limits. On the 4th limb it dips on average to NE: 65–70° at an angle of 35–40°. In passing across the fold hinge, it, like the bedding, changes its dip direction to the opposite—from 60–75 to 240–245; but, in contrast to the bedding, it becomes somewhat flatter and, apparently, merges with exoplane IV. In other seams, both in the Koksovaya mine and in 3 and 3-bis, it behaves in exactly the same way and everywhere is expressed almost as distinctly as the bedding. Everywhere it bears signs of slickensiding, indicating intraseam movements that took place along it; moreover, on the odd-numbered limbs it is expressed still more distinctly than on the even-numbered ones, owing to its coincidence with the Exo—IV plane.

The end plane behaves somewhat differently. As is evident from the table, it dips steeply (70–85°) to the south-southeast and cuts the seam almost across its strike. Thanks to this orientation, when passing through the hinge of the fold it almost does not change its conditions of occurrence. At the same time, it does not participate in intraseam movements and therefore usually bears no traces of slickensiding and, in general, is expressed much more weakly in comparison with the other planes. In the splitting of coal it always plays only a secondary role.

The noted regularities, clearly established in the IV Internal seam, retain their force also in the other seams we investigated—the III Internal and Gorely in the field of the Koksovaya mine, and also in the same seams and in Moshchny in the field of mine 3 and 3-bis. This, in turn, allows one to think that they have general significance and may, without particular danger, be extrap-

…were extrapolated to neighboring sectors of the mine field, where no direct observations had been made.

The very same cleavage planes, and with approximately the same elements of occurrence, are also observed in the enclosing rocks, as is evident from summary Table No. 5, which gives observations on the cleavage of the enclosing rocks made in backfill quarries and in collapse funnels on the surface.

B. Exogenous planes.

1. Exo I-a $\dfrac{184—210}{54—82}$ Southern.

Of the exogenous planes, judging from our observations, the plane we have called Exo I-a is of greatest importance. This plane has a very wide distribution and has been recorded at almost all points of our observations in the coal. It plays a primary role in the splitting-off of coal in the faces and is sometimes exposed over a great length, in the form of continuous slickensided surfaces. But its surface does not constitute an ideal plane. It is curved and wavy, like corrugated iron. Because of this, both the strike and especially the dip angles, when measured even in a single exposure, vary within fairly wide limits, sometimes taking on reverse values. But in general the average values of the elements of its occurrence are maintained quite well, not only at individual points of the seam, but also over all seams and wings, independently of their orientation.

Especially sharp fluctuations of this plane are observed in the Gorely seam, where it more often acquires reverse dips. This may be due to the fact that here the influence of some other cleavage plane is admixed with it, namely III bis (northern), but in this case it is difficult to isolate it.

The average values of the azimuths of occurrence of this plane at all points of observation, both in the field of the Koksovaya mine and in 3 and 3-bis, fluctuate within the following limits: the dip azimuth—from 184 to 210°, and the dip angle—from 54 to 82°, with the exception of the Gorely seam, where the dip azimuth reaches 216°, and the angle up to 88 and even 100° (reverse 80°).

It is interesting to note that the Exo I-a plane, while affecting all coal seams, apparently almost does not pass into the side rocks. Of 8 observation points in the rocks it was noted only in one, and there it is expressed very weakly.

Exo I-bis $\dfrac{310—340}{20—40}$ Northwestern.

Together with the plane described, another is often observed, almost perpendicular to it and apparently associated with it, which we have called Exo I-bis. It has almost as wide a distribution as Exo I-a and appears equally distinctly both in the field of the Koksovaya mine and in 3 and 3-bis. But in

in the field of the Koksovaya mine it is observed chiefly along IV Internal on limb 4 (the eastern limb of the Small anticline), and it is more distinctly expressed in the south than in the north. Along III Internal it is very weakly expressed, and on Gorely it was not observed at all. As the hinge of the fold is approached, it apparently dies out and almost does not pass onto limb 5. In the field of mines 3 and 3-bis, however, it is observed in almost all seams, and moreover on both the eastern and western limbs of the synclines.

The average elements of attitude of the plane vary: dip azimuth 310–340, dip angle 20–40, with rare exceptions 295–51—the only observation on seam III Internal at the Koksovaya mine, and 333–18—on the Moshchny seam in the field of mines 3 and 3-bis.

For coal cleaving, this plane will have substantial importance along seam IV Internal in the south of the Koksovaya mine and along Gorely, IV and partly III Internal in mine 3 and 3-bis.

This plane is sometimes also observed in the country rocks, chiefly above the field of mines 3 and 3-bis, and in places is well expressed. From these data it would seem that the importance of the exo I-bis plane increases toward the south.

Exo II-a $\dfrac{95—115}{50—75}$ Eastern.

This plane is also rather widely distributed. It is especially widely developed in the south, in the field of mines 3 and 3-bis. Here it was encountered in all the seams investigated and in places plays a substantial role in coal cleaving. In the field of the Koksovaya mine it is well expressed on limb 4 only along seam IV Internal in the south, and gradually dies out northward, as the hinge of the fold is approached. Along seams III Internal and Gorely it has not been recorded. On limb 5, on the contrary, it is expressed distinctly, beginning at the very hinge of the fold, and affects not only IV but also III Internal and Gorely. In places it is also observed in the enclosing rocks, independently of the fold limbs, both in the north and in the south, and is expressed rather distinctly.

The plane preserves its conditions of attitude rather well. The average dip azimuth usually varies within the limits 95–115°, with rare deviations to 87 in one direction and 120 in the other. The dip angles change rather smoothly and regularly; in the south, in the field of mines 3 and 3-bis, they range from 70 to 80°, while in the north, in the field of the Koksovaya mine, from 45 to 65.

Exo II-bis $\dfrac{45—60}{55—70}$ Northeastern.

This plane is manifested only in the field of mines 3 and 3-bis along the Gorely seam and partly Moshchny, on the western limb of 5

syncline. In the Gorely seam it is encountered at almost all observation points and plays, if not the principal, then a very significant role in the cleavage of the coal. The distances between fractures are from 1 to 25 cm, usually about 5 cm. The fracture surfaces bear a magnificent polish, indicating fairly intensive movements along them.

The dip azimuth at individual points varies within the range 45–60°, and the dip angles from 55 to 70°.

With plane II-a it forms an angle of 60°, and it seems to us that it is conjugate with it. In analyzing the observational data for mines 3 and 3-bis, it may be noted, in any case, that both planes occur there together; moreover, where one dies out, the other flares up.

Plane II-bis is confined to the western limb of the syncline; it may therefore be thought that it develops predominantly or exclusively on limbs dipping to the east, which in the Koksovaya mine corresponds to their odd numbering and, in particular, to limb 5. We do not observe it there because the elements of its attitude coincide with the elements of the bedding plane, and it probably merges with the latter.

\[ \text{Exo III-a } \frac{250—280}{60—75} \ \text{ Western.} \]

This plane and the exo III-bis described below are apparently also conjugate and constitute a third pair of exogenous planes, with a dihedral angle between them of about 75°. However, both these planes are in general little developed and are nowhere encountered together. Plane III-a is steep. It dips at an angle of 60–75° to the west, in the direction 250–280°. In the field of the Koksovaya mine it has been recorded only along the IV Internal seam of limb 4, where it is close to the bedding plane and probably partly merges with it. Therefore it plays no independent role in the cleavage of the coal. In the field of seams 3 and 3-bis, however, along the Gorely seam of syncline 5 it is rather clearly differentiated and participates in certain combinations in the cleavage of coal at the face.

\[ \text{Exo III-bis } \frac{4—12}{35—50} \ \text{ Northern.} \]

This plane, like the preceding one, is observed only sporadically. It dips at moderate angles to the north, forming with the preceding one a dihedral angle of 75°. Unlike III-a, it is observed only in the Koksovaya mine along the III and IV Internal seams and, moreover, exclusively on limb 5. Along the IV Internal seam it is very well expressed and sometimes plays some role in the cleavage of the coal. In general, however, these two planes have no substantial significance.

It is interesting, however, to note that, despite its weak manifestation in the coal seams, it is observed more often than other exogenous planes in the side rocks (see Table 5).

In addition to the six exogenous planes listed, there is one more plane, dipping at an angle of 35–50° to the southeast: 230–250°. This plane can be noticed and distinguished only in steeply dipping seams of even-numbered limbs, or in gently dipping seams of odd-numbered ones. In particular, in the area of the Small Anticline of the Koksovaya Mine, we observed it only along the Gorely seam in the 4th limb in the south, where the seam has a dip of 60° and more.

Where the seam flattens, it merges with the bedding plane, and in the 5th limb with the main plane. Therefore its recognition here is impossible. It is very probable that there is also a conjugate plane associated with it, which in the even-numbered limbs replaces the main one, and in the odd-numbered limbs—the bedding plane. However, such a plane, at least in part, is the exo III-bis already discussed above.

As for the connection between exocleavage planes and tectonics, we still do not have sufficient data for an analysis of this question. There is no doubt that some cleavage planes coincide with tectonic disturbances of the 2nd and 3rd orders. But whether cleavage is a consequence of these disturbances or, conversely, the fractures of minor disturbances made use of cleavage cracks, as lines of least resistance, and in one way or another adapted themselves to them, remains an open question.

It seems to us that exocleavage and the tectonics of the Kuzbass are the result of a single natural process—the folding of the coal-bearing deposits by the Salair block thrust over them. According to our investigations of the tectonic disturbances of the Koksovaya Mine field,^1 the Salair Ridge was not only thrust over the deposits of the Kuznetsk Basin, but was also displaced significantly to the south. As a result, the folded structures that had existed earlier and were renewed by this pressure were broken by a series of large longitudinal thrust-strike-slip faults and smaller diagonal and transverse disturbances of the second, third, and higher orders; naturally, the higher the order of a disturbance, the smaller its amplitude. The fractures of exogenous cleavage observed by us bear clear traces of slickensiding, indicating more or less considerable displacements along them, and, in the final analysis, they are the same tectonic disturbances, only of higher orders. Thus, the emergence both of the complex tectonics of the Prokopyevsk district and of the no less complex cleavage lattice of its thick seams is, in our opinion, due to a single geological process and belongs to one geological time.

Having become acquainted in general terms with the structure of the cleavage lattice, its variations in space, and the nomenclature of the cleavage planes we have identified, let us proceed to an analysis of the influence of these planes and their combinations on the splitting of coal in the faces of stoping workings.

^1 A. A. Belitsky.—Method for searching for the displaced limb of a seam. Manuscript, 1936, Tomsk.

The Influence of Cleavage on the Stability of Stoping Workings

The influence of cleavage on mining operations, especially on stoping workings, is exceptionally great. Here cleavage, on the one hand, plays a useful role by facilitating the breaking of coal; on the other hand, it is often the main cause of accidents, since under certain relationships between the exposed planes of coal in a stoping working—especially the roof of the working—and the cleavage planes, the coal along them often separates in large blocks and falls out, causing the formation of large domes, damage to the support, falls of the working space, and even accidents involving people.

Our task included the study of cleavage chiefly from the latter point of view; therefore, along with studying the frequency of occurrence and the degree of expression of cleavage planes, tracing them along the strike, and so forth, we paid particular attention to the question of the splitting-off of coal along these planes in stoping workings.

Below we give a description of the splitting-off of coal along cleavage planes in the various mining systems used in seams IV Internal, Burnt, and III Internal of the Koksovaya and 3–3-bis mines of the “Stalinugol” Trust.

Koksovaya Mine named after Comrade Stalin

1. “Herringbone” System

(Observation point 6)

This system of mining thick seams consists of the following. The seam is divided into nearly square pillars, somewhat elongated along the rise; their extraction is carried out from below upward by diagonal slices with a double-sided face. The “herringbone” system, as an experimental system at the Koksovaya Mine, was first laid out in seam IV Internal of the 4th wing—south, 260 m from the main crosscut of the mine. The slopes are inclined in different directions from the central furnace at an angle of 35–40°.

Coal extraction under this system is carried out in the following manner. First the “ridge” is cut, i.e., a horizontal platform at the intersection of two slopes. Then, from this platform, at the roof of the seam, they begin to “curl,” i.e., to extract from top to bottom the first strip of the diagonal slice, 2.5 m high and 1.5–2 m wide. After this the remaining strips are extracted, likewise from top to bottom, in the order from roof to floor. After the slice on one slope has been worked for the full thickness of the seam, they proceed to extraction of the other slope, while the first is being packed at that time. After the extraction of the second slope it is packed, and then the “ridge” is again cut, after which the work is repeated in the same order. Since the coal is extracted along the rise of the seam, the floor of the slopes is stowing material, and the roof is coal. The breaking of coal is carried out by blasting.

The general geological characteristics of Seam IV Inner—south amount to the following. The seam occurs in wing 4, i.e., in the western wing of the Small Anticline. This wing, like all the western wings of the anticlinal folds of the Prokopyevsk deposit, is comparatively weakly disturbed. The southern crosscut of IV Inner encountered only one small disturbance of the type of a discordant reverse fault, 100 m south of the main crosscut of the mine and 160 m north of the place where the “herringbone” was laid out. The horizontal amplitude of this disturbance is 2.5 m. Thus, it may be considered that the stoping working is located in a comparatively calm part of the seam.

The normal thickness of the seam is 9.2 m. The seam thickness is well maintained along strike and dip.

The roof of the seam—sandstone—is very stable. It is exposed on both slopes of the “herringbone” over large areas and does not require timbering. The floor of the seam—sandy argillite—is less stable than the roof, but it has no effect on coal extraction.

In the coal seam there are two small partings of rock. The first parting is graphitic argillite, 1.7 m from the roof, with a thickness of 0.18 m. The second parting is dull coal with an inclusion of oolitic ironstone, 4.5 m from the roof, with a thickness of 0.08–0.10 m. The coal near the roof is strong, but as it approaches the floor it becomes weaker. In the very floor of the seam there is a band of soft coal 0.25–0.30 m thick, which is well maintained for a considerable distance along the strike and dip of the seam.

At 4.8 m above the roof of Seam IV Inner lies the coal seam “Conductor,” 1.65 m thick, which is usually not mined; above it lies a thick bed of sandstone.

a) Northern slope of the “herringbone.”

On the northern slope of the “herringbone” the following planes were found.

Table 6.

Bedding	Bedding	Endoplanes	Endoplanes	Endoplanes	Endoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes
Az.	angle	Main	Main	End	End	I-a	I-a	I-bis	I-bis	II-a	II-a
Az.	angle	Az.	angle	Az.	angle	Az.	angle	Az.	angle	Az.	angle
250	60	58	29	148	74	196	75	325	27	97	60

Of these planes, the bedding, the main plane, exoplanes I-bis and II-a (Fig. 13) mainly influence the cleavage of the coal, and this influence is manifested in several combinations.

First combination—bedding, main plane, and end.

In this combination, the leading role in the cleavage of the coal belongs to the bedding and to the principal plane. Their surface is smooth, lustrous, and sometimes, especially in the floor of the seam, bears a clearly expressed striation. These two planes are mutually perpendicular, but in plan their traces intersect at a very acute angle, equal to 12°.

The aggregate of these two planes, and their interaction, exert a great influence on the extraction of coal and on the stability of the roof-and-floor mass of the chute.

As was already noted above, the coal is extracted in diagonal strips located in the plane of the seam. Consequently, the wall of the strip ought to be along the bedding. In reality, however, owing to the cleavage of the coal along the principal plane, the wall of the strip usually does not coincide with the bedding. The principal plane, forming a right angle at its intersection with the bedding, falls away from the wall of the strip and at the same time overhangs the worked-out space of the previously extracted layer (Figs. 14–15). Therefore the coal, having easily cleaved along the principal plane, slides along the bedding, as along a steep inclined plane, spontaneously widening the cross section of the strip. This cleavage, as the strips are shifted from the roof toward the floor, is not uniform. In the roof of the seam the cleavage of the coal occurs mainly along the bedding, while the principal plane plays only an auxiliary role (Fig. 14a). In the floor of the seam, on the contrary, the greatest cleavage occurs along the principal plane, as a result of which the wall of the strip falls in a direction opposite to the dip of the seam (Fig. 14b), thus masking the actual elements of its occurrence.

During extraction of the strip these two planes play a positive role, considerably facilitating the work of undercutting. According to the miners, when approaching the floor it is enough to set one borehole below, and the coal, cleaving along the principal plane, itself separates from the face and goes almost by gravity.

In the roof of the working these two planes play a negative role. Here both the principal plane and the bedding overhang the worked-out space, as a result of which the coal, easily falling out along these planes, forms a series of domes, sometimes reaching more than 1 m in height and 1.0–1.5 m in width (Fig. 15). Often in the roof of the working one can observe coal along these planes which, having cleaved off, is barely held on the support. These places have to be watched especially carefully by the technical supervision in order to avoid premature and unexpected falls of coal.

The shape of a block that has fallen out of the roof mass of a working is usually either pyramidal or wedge-shaped (Fig. 16); in the formation of such a shape, in addition to the planes enumerated above, the end face and the plane of the roof of the working also take part, the latter sometimes coinciding with exoplane 1-bis.

The second combination—cleavage plane 1-bis, stratification, face, and partly the principal plane.

This combination of planes is the most dangerous, creating a constant threat of an accidental fall of coal, as a result of which the stoping working is not infrequently put out of operation for a prolonged period. The decisive role in this combination of planes in the separation of coal belongs to cleavage plane 1-bis; the other planes are of secondary importance.

Cleavage plane 1-bis on the northern flank of the “herringbone” is exceptionally sharply expressed. Its surface here, as in all places where we observed it, is irregular, strongly undulating, with clearly expressed striations and even deep furrows. The greater influence of this plane on the separation of coal on the northern flank of the “herringbone” is explained above all by the fact that it either coincides with the roof of the flank, or—still worse—cuts it at an acute angle, overhanging the mined-out space (Fig. 13). Therefore coal which, under the force of its own weight, tends to separate from the general mass of the seam, most readily separates along cleavage plane 1-bis, as along the line of least resistance. This is also facilitated by the absence of a rigid bearing surface at the support, which, resting on the loose foundation of fresh packing, under the pressure of the overhanging masses gives a considerable settlement, thereby promoting cracking of the coal in the roof thickness.

The most dangerous part of the seam, where the separation of large blocks of coal mainly takes place, is the part 2–3 meters thick adjoining directly the roof of the seam. Here, often, especially after extraction of the entire layer and the cutting of the “ridge,” under the action of the weight of blocks separated along the planes of this combination, enormous gaping cracks are formed between individual blocks, and also between them and the roof of the seam; the width of their opening reaches up to 0.3–0.4 m (Fig. 17). Closer to the floor, separation of coal along cleavage plane 1-bis is observed much less often, and sometimes it is even difficult to detect.

The shape and dimensions of individual blocks are rather varied. Most often one encounters the form of an elongated parallelepiped, whose faces, owing to the strongly undulating surface of cleavage plane 1-bis, are in most cases oval. The largest dimensions of blocks in cross-section are 2.0 × 1.0 m, with a length of 3–4 and even more meters (Fig. 18).

As for cleavage planes II-a and I-a, the first plane is traced mainly in the floor of the seam and, in combination with the principal plane and the face, sometimes has considerable significance in the separation of coal. The second plane, however, appears comparatively weakly and has no influence on the separation of coal.

b) Southern flank of the “herringbone.”

On this flank the following planes were encountered.

Table 7.

Bedding	Bedding	Endoplanes	Endoplanes	Endoplanes	Endoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes
Az.	Dip	Main	Main	End	End	I-a	I-a	I-bis	I-bis	II-a	II-a
Az.	Dip	Az.	Dip	Az.	Dip	Az.	Dip	Az.	Dip	Az.	Dip
259	61	57	57	156	69	196	75	325	27	103	57

In addition to these planes, a pressure crack was encountered here with dip azimuths of 156 and 138, running parallel to the roof of the slope.

The splitting off of coal in the southern slope is influenced by the bedding, the main plane, and exoplane II-a (Fig. 13). Exoplane I-bis plays a secondary role and, in general, can be traced only with great difficulty in the working, since it intersects the roof of the workings almost at a right angle. Here these planes influence the splitting off of coal in several combinations.

First combination — bedding, the main plane, and the end face.

In this combination, as in the northern slope, the leading role in the splitting off of coal belongs to the bedding and the main plane. The interaction of these planes affects the stability of the roof mass of the working, but to a lesser degree than in the northern slope, since in the present case the main plane dips discordantly with the dip of the southern slope (Fig. 13).

The formation of pressure cracks is associated with this combination of planes. These cracks were detected already during the cutting of the ridge and were then readily traced throughout the entire slope. At the time of observation one of these cracks was clearly visible in the face of the slope, where it cut the entire seam from the roof down to the very floor (Fig. 19). Its surface, representing a forced fracture, was uneven and angular, with no slickensides or striations characteristic of exoplanes. The crack was gaping; the amount of opening was 0.1–0.25 m.

Examining the surface of the crack carefully, we noticed that it is an uneven, knobby surface, studded with blunt triangular pyramids formed by a combination chiefly of endogenous cleavage planes of bedding, the main plane, and the end face.^1

The elements of the occurrence of this crack are close to the elements of occurrence of the slope, as a result of which it is almost parallel to the latter.

^1 Strictly speaking, this will of course not be a pressure crack, since the latter form independently of cracks of natural cleavage; however, by the nature of its formation it is close to them.

This crack caused no accidents, at least during the period of observation. At the same time, however, it created a constant threat of collapse, required careful supervision and thorough support. During extraction the coal broke off along it in large blocks of up to \(5 \times 6 \times 7\) cubic m, which caused certain difficulties and even danger when breaking down the coal.

The second combination—exoplane II-a, bedding, and the principal plane.

The interaction of these planes has a great influence on the spalling of coal near the floor of the seam. The leading role here belongs to exoplane II-a, which is especially sharply expressed at the floor of the seam.

In the present case, when a layer is being extracted from the roof toward the floor of the seam, the coal spalls from the wall of the strip along the principal plane and especially along exoplane II-a, which dips in the opposite direction relative to the dip of the seam, forming with it an angle equal to \(60^\circ\). Thus this plane overhangs the worked-out space of the lower layer and, as a result of the settling of the packing, the coal is easily separated along it from the general mass of the seam, forming large gaping cracks along the entire working (Fig. 20). The spalled part of the seam, as a result of settling, is moreover intensively broken along the bedding and the principal plane into separate pieces of the most varied sizes. It must be noted, however, that such spalling of the coal, occurring mainly at the floor of the seam, facilitates extraction of the coal rather than creates a danger of accident. Since the angle of dip of the chute does not exceed \(40^\circ\), i.e., is less than the angle of natural slope, these pieces do not roll downward, but remain in place.

In addition to the planes listed, on the southern chute two cases of doming were recorded near the floor—on 13.XII.37 and 19.II.38; moreover, in the opinion of the mine geologist V. A. Azimov (1), these domes formed chiefly under the influence of exoplane I-a. Meanwhile this plane in the given working can be traced only with great difficulty and, owing to its orientation, cannot by itself cause doming. It should be thought that these domes formed as a result of the combined influence of exoplane I-a, exoplane II-a, and the principal plane, i.e., in the same way as the dome formed in the neighboring stoping working described below.

2. Single-chute face.

(Observation points X, 32, and 33).

This system differs from the preceding one only in that, instead of two chutes, it has only one.

This stoping working was also laid out in seam IV of the Inner 4th wing—south, beside the “fir-tree” system (observation point X), and therefore the geological conditions are almost the same. Here

it can only be noted that in the roof of the seam, in places, there is a small interbed 8–10 cm thick, often consisting of an alternation of thin layers of sandstone and coal. This interbed separates comparatively easily from the roof, but it is not found everywhere, occurring mainly in the “wrinkles” of the roof. In general, the roof is stable and holds well even when it is exposed over a large area. Only in one place did we observe the indicated interbed separating from the roof as a slab and requiring that it be secured by a strut. The dip of the drift is directed south, i.e., analogous to the southern drift of the “herringbone,” at an angle of 38°.

Table 8.

Bedding	Bedding	Endoplanes	Endoplanes	Endoplanes	Endoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes
Bedding	Bedding	Main	Main	Face	Face	I-a	I-a	I-bis	I-bis	II-a	II-a	IV	IV
Az.	Ang.	Az.	Ang.	Az.	Ang.	Az.	Ang.	Az.	Ang.	Az.	Ang.	Az.	Ang.
253	62	32	44	156	80	193	73	313	30	100	65	231	35

The splitting of the coal here is influenced chiefly by bedding, the main plane, exo I-a, and exoplane II-a. Exoplane IV appears sporadically in the roof of the seam and plays a certain role only in combination with other planes. Exoplane I-bis is traced only in the roof of the drift and, just as in the southern drift of the “herringbone,” plays no role, since it cuts the roof of the drift almost at a right angle. The face plane is still weakly expressed and has almost no effect on the splitting of the coal.

All these planes influence the splitting of the coal in two combinations.

First combination—bedding, the main plane, and exoplane IV.

The bedding and the main plane are very well expressed. Their surfaces are shiny and bear slickensides and striations. Exoplane IV is clearly traceable only in the roof of the seam. This plane cuts the roof of the working at an acute angle; here, however, it does not have the importance that exoplane I-bis had in the splitting of coal in the southern drift of the “herringbone.” Incidentally, it should be noted that exoplane IV does not have a regional distribution. It has been encountered only at two observation points in the Koksovaya Mine named after Comrade Stalin.

The leading role in splitting in this combination belongs to the bedding and the main plane. Both these planes overhang the mined-out space, as a result of which the coal splits along them into large blocks. The latter settle onto the support, owing to which gaping cracks form between them, as well as between them and the roof; the width of the openings reaches 0.1–0.2 m (Fig. 21). According to the miners, splitting of the coal into large blocks in the roof of the seam in this working is a common phenomenon. Most often the blocks that split off …

blocks have the form of an elongated parallelepiped with maximum dimensions of \(1.8 \times 1.3 \times 3.0\) m.

The causes of the separation of coal in large blocks in the roof of the seam are evidently the same as on the northern slope of the “herringbone”; however, the scale of separation is somewhat smaller, since in the present case the leading role belongs to bedding and to the principal plane, with the exoplane IV being of secondary importance, whereas on the northern slope of the “herringbone” the leading role in separation belonged to exoplane I bis, which chiefly caused the emergency separation of coal.

Second combination—exoplane 1-a, exoplane II-a, and the principal plane.

This combination of planes in the given working causes emergency separation of coal. Thus, on 16 September 1938, along these planes, in the brow part of the working of the undercutting furnace, a large dome 2.5 m high collapsed (Fig. 22). The leading role in the separation of coal in this combination belongs to exoplane 1-a. This plane, having an almost vertical dip, is oriented in the coal seam so that it either coincides with the brow plane or cuts it at an acute angle. Therefore, as a result of shocks from blasting operations, the coal at the top separates along the principal plane and exoplane II-a, and then easily slides down along exoplane 1-a, often creating, as we shall see below in describing the system of diagonal faces, large domes.

By the same system, seam IV Inner—north is being worked in the 5th wing, where at the time of observation there were two stoping faces 125 m south of the main crosscut of the mine. Both workings are located close to one another and are separated only by a small pillar. The slopes dip northward at an angle of \(36\)—\(40^\circ\).

This part of the seam is in unfavorable geological conditions. In general, the eastern limb of the small anticline, like all eastern limbs of the anticlinal folds of the district, is considerably more intensely fractured. In addition, this part of the seam is in immediate proximity (70 m to the west) to a large disturbance of the JJ type, an unconformable reverse fault with a horizontal displacement amplitude of up to 150 m. This same disturbance should definitively cut off seam IV Inner 170 m south of the described stoping workings. In addition, 100 m south of the stoping workings there passes a disturbance, also of the type of an unconformable reverse fault, with a horizontal amplitude of 25 m. Undoubtedly, all these disturbances have had a major influence on the coal seam, especially on the cleavage planes, which are exceptionally clearly expressed at this place.

The normal thickness of the seam ranges from 8.5 to 8.9 m. The roof of the seam, represented by sandy argillite, is fairly stable. Its surface is uneven and hummocky. Above it, 4.5 m away, lies the Provodnik seam, 1.2 m thick, whose roof is fine-grained sandstone. The floor of the seam consists first of argillite, 0.75 m thick, and then sandstone.

There are two partings of rock in the coal seam. The first parting is a graphite-like argillite, 0.15–0.20 m thick and 2 m from the roof of the seam. The second parting is oolitic ironstone. Neither of these partings persists along the strike: their thickness sometimes increases, sometimes decreases, and at times they disappear altogether.

In both of these workings the following planes were observed (Fig. 23).

Table 9.

Bedding	Bedding	Endoplanes — Principal	Endoplanes — Principal	Endoplanes — Face	Endoplanes — Face	Exoplanes — I-a	Exoplanes — I-a	Exoplanes — II-a	Exoplanes — II-a	Exoplanes — III-bis	Exoplanes — III-bis
Az.	Dip angle	Az.	Dip angle	Az.	Dip angle	Az.	Dip angle	Az.	Dip angle	Az.	Dip angle
60	69	253	31	164	75	176	47	104	67	12	34

All these planes are equally well expressed here, with the exception of the face plane, which is usually weakly expressed and plays only an auxiliary role.

These planes affect the cleavage of the coal in three combinations.

First combination—bedding, the principal plane, and exoplane III-bis.

The influence of these planes on the cleavage is analogous to that on the northern slope of the “yolochka” in seam IV of the Inner 4th wing—south. Here the leading role belongs to exoplane III-bis, which almost coincides with the roof of the working.¹

The principal plane and exoplane III-bis are situated in the seam in such a way that they overhang the mined-out space. Because of this, at the face of the strip (Fig. 24), chiefly in the near-roof part of the seam, the coal breaks along these planes and falls away in large blocks. These blocks, separating from the general mass of coal, press by their weight on the support; under this action the support settles, and the blocks settle with it. Thus, between the blocks, and also between the blocks and the roof, gaping cracks up to 0.30 m are formed.

These same planes also exert a great influence on the cleavage of the coal in the roof of the working (Fig. 25). Here, too, large blocks of coal are cleaved off. Because of this the roof of the working is torn upward, so that the height of the bed, instead of the normal 2.2 m, sometimes reaches 4.5 m, and in places of major collapses, where domes are formed, as much as 6–7 m.

The shape of the detached blocks is usually an elongated parallelepiped. The dimensions of such blocks reach up to 5–6 m in length and 0.6 × 1 m in cross-section.

¹ This plane, in the analysis of the cleavage lattice, is singled out as a separate plane, with a special index, but it is possible that it is plane 1-bis, only having changed its dip azimuth.

The second combination—bedding, the principal plane, exoplane II-a, and exoplane III-bis.

The leading role in the cleavage of the coal in this combination of planes belongs to the bedding, the principal plane, and exoplane II-a. Large domes form along these planes. Thus, on 15 September 1938, in slope No. 2, a dome 7 m high formed. An enormous block of coal (Fig. 26) split off upward along the main plane, along the sides along the bedding, and lengthwise along exoplane II-a. Within this block the coal broke up into separate pieces along plane III-bis. This block knocked out several sets of supports, the restoration of which required several shifts.

The third combination—bedding, exoplane I-a, and exoplane II-a.

This combination of planes creates danger chiefly in the face part of the working. The leading role in cleavage belongs to exoplane II-a. Here these planes overhang the mined-out space; therefore the coal readily cleaves along them.

3. System of diagonal slices with extraction by long pillars along the strike

Unlike the preceding systems, here mining is carried out by long pillars along the strike. For the extraction of coal, the level is divided into two sublevels, in each of which a diagonal slice is laid out. The actual process of coal extraction differs hardly at all from the preceding systems, and therefore we shall not dwell on it.

At present, seam IV of the Inner 4, wing—north (observation points 1, 2), is being worked by diagonal slices. Here two diagonal slices have been laid out. At the time of observation, the lower one was 165 m from the main crosscut of the mine, and the upper one 135 m from it. Both diagonal slices dip south at an angle of 38–40°.

The geological characteristics of seam IV of the Inner 4, wing—north, are as follows. At 170 m north of the main crosscut, i.e., almost at the site of the lower diagonal slice, there passes a comparatively large diagonal disturbance of the type of a concordant reverse fault. The azimuth of dip is 282°; ∠ 72. The horizontal amplitude of displacement is 25 m. The diagonal slices are laid out on the footwall side of this disturbance. The lower diagonal slice is laid out directly at the point where the roof cutoffs of the hanging and footwall wings of the disturbance intersect with the main drift of the 215 m level; therefore the thickness of the seam in the lower diagonal slice proved to be doubled. The upper diagonal slice, owing to the fact that the lines of intersection dip southward, is somewhat removed from the disturbance and is located—

located 50 m from the extreme southern cut-off of the roof of the hanging wall of the fault. Apart from this fault, the main drift of the 215 m horizon encountered no further faults.

The normal thickness of the seam is 8.9 m. The seam roof consists of fine-grained banded sandstone. The roof is unstable, heavily fractured, with fractures of endogenous cleavage predominating, evidently accentuated at the fault. Owing to the weak roof, and in order to avoid contamination of the coal, the roof is not exposed during extraction of the seam; instead, an undisturbed band of coal up to 0.5 m thick is left. At 1.2 m above the roof of seam IV Internal lies the Provodnik seam, 1.2 m thick. The roof of the Provodnik is likewise fine-grained banded sandstone. The floor of the seam is first a sandy argillite 0.3 m thick, and then sandstone.

Within the coal seam there are three argillite partings. The first parting, 0.08 m thick, is 4.1 m from the roof; the second parting, 0.16 m thick, is 5.6 m from the roof; and the third parting, 0.1 m thick, is located 1.5 m from the floor.

The northern part of seam IV Internal of wing 4 differs markedly from the southern part of this seam in that here the coal is considerably more crushed, owing on the one hand to its proximity to the closure of the fold, and on the other to the presence of the fault mentioned above. All planes are exceptionally sharply expressed here, especially in the floor, where the distinction between endocleavage and exocleavage is completely lost, since all the planes bear clear traces of slickensiding. It is interesting to note that even the face plane, which is usually very weakly expressed, here in its manifestation differs in no way from the other planes, and therefore acquires greater significance in the splitting of the coal.

In what follows we shall describe only the upper diagonal layer. In the lower diagonal layer systematic observations were not made, since a major accident occurred there and access to it was impossible.

In this working we observed the following planes.

Table 10

Bedding	Bedding	Endoplanes	Endoplanes	Endoplanes	Endoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes
Az.	angle	Main Az.	Main angle	Face Az.	Face angle	I-a Az.	I-a angle	I-bis Az.	I-bis angle
255	60	65	40	145	85	185	70	280	20

The splitting of the coal is influenced by bedding, the main plane, the face, and exoplane I-a. Exoplane I-bis, as on all southern slopes, is of no substantial importance, since it cuts the roof of the working almost at a right angle (Fig. 13).

The leading role in the cleavage of coal here belongs to exoplane 1-a, which, in combination with the other planes, creates a constant threat of accidents arising, equally in the roof of the working and during advance of the face. This is also promoted by the presence of water in this working. By wetting the cracks, the water reduces cohesion and thereby facilitates the cleavage of coal along them.

In the roof of the working, especially closer to the floor of the seam, domes are often observed, the form of which in most cases is a triangular pyramid bounded by the planes: exo—1-a, end, and bedding. Sometimes the dome has the form of a truncated pyramid; then the plane of truncation is the principal plane. The base of such a pyramidal dome is usually close to an equilateral triangle; the height reaches 0.6–0.8 m. All these planes overhang the mined-out space; therefore, when all the planes are sharply expressed, the coal readily falls out along them.

In addition to such, relatively small, domes, in the roof of the working there is often observed cleavage of coal in large blocks along the planes: exo—1-a or end, bedding, and the principal plane. Sometimes these blocks are formed near domes, being as it were their further continuation, but sometimes they are formed independently (Fig. 27). Not infrequently such blocks of coal, if not supported in time, are the cause of serious accidents.

These planes also present a considerable danger in the side part of the working, since exoplane 1-a cuts the side plane at an acute angle. As a result, the coal, chiefly along exoplane 1-a, and also along the principal and bedding planes, cleaves off from the side plane in large blocks in the form of elongated quadrangular prisms, the dimensions of which reach 1.0 × 1.5 × 3.0 cubic m. Thus, for example, during an examination of this working on 20.9.38, after one of the successive layers had been mined and its stowing had begun, we observed in the side part of the working large blocks that had cleaved off from it and were piled up haphazardly one upon another.

In general it must be said that this stoping working, owing to the intensive cleavage of coal along the cleavage planes on all exposed planes of the working, was constantly in an emergency condition; therefore it systematically failed to fulfill the coal-production plan.

4. System of long pillars along the strike with extraction by a continuous face, “Lava.”

The principal difference of the lava from the preceding systems consists in the fact that the plane of exposure of the coal in the face is vertical and is directed along the dip of the seam, whereas in diagonal layers the boundary of the layer being extracted is always inclined

and diagonally with respect to the seam. Such an orientation of the exposed plane contributes to its greater stability, since the coal does not overhang the worked-out space. In addition, we observed this system in the less thick seam—III Internal—which, moreover, was not extracted to its full thickness but, in effect, was worked wastefully in a single inclined slice, leaving large masses of coal on the hanging and lying sides. Thus, for example, in longwall No. 1 more than 1.5 m of coal was left in the floor of the seam, and in longwall No. 2 about 2.5 m in the roof.

It is clear that under such conditions this system offers considerable advantages in terms of face stability, all the more so because in this case the face advances much more rapidly and, consequently, the coal does not have time to settle and crack.

4th wing.

We observed this system of workings in seam III Internal of the 4th wing—south. Here two longwalls are operating simultaneously. The first is 180 m (observation point 28), and the second 400 m south of the main crosscut of the mine (observation point 27). The first longwall, extracting coal along the strike of the seam, advanced from south to north, and the second from north to south; thus, we were able simultaneously to observe the influence of cleavage planes on faces advancing in opposite directions.

The geological characteristics of seam III Internal of the 4th wing—south are as follows. Here a substantial disturbance was encountered 70 m south of the main crosscut of the mine and 110 m north of the first longwall, described above in connection with the geological description of seam IV Internal of the 4th wing—south. No further disturbances were encountered by the southern drift of this seam; therefore it may be considered that the extraction workings are under normal conditions.

The average normal thickness of the seam, equal to 5.6 m, varies within this section from 5.3 m—in longwall No. 1—to 6 m—in longwall No. 2. The roof of the seam is represented at first by argillite and then by sandstone. The roof is stable. The floor of the seam is represented by sandstone. The seam contains two interbeds of graphite-like argillite: the first 0.8 m from the roof, 0.2 m thick, and the second 3 m from the roof, 0.05–0.10 m thick. In addition, in the coal seam, 3.3 m from the roof, there is a small interbed of soft coal 0.05 m thick.

The coal seam may be divided into two benches. The first bench—from the roof to the interbed of soft coal. Here the coal is fairly strong, dull, with frequent interbeds of shiny ingredients, with clearly expressed cleavage planes. The second bench—from the interbed of soft coal to the floor of the seam—has coal that is less strong and highly crushed, as a result of which it is rather difficult to distinguish cleavage planes in this coal bench.

a) Longwall No. 1. Observation point 23. Movement of the face from south to north.

Here we observed the following planes.

Table 11

Bedding	Endoplanes	Endoplanes	Exoplanes	Exoplanes
Bedding	Main	Face	I-a	I-bis
263—64	57—36	157—80	199—60	301—50

The cleavage of the coal here is influenced by the bedding, the main plane, and exoplane I-a. Exoplane I-bis is expressed much more weakly than the other planes and plays a secondary role in the cleavage of the coal. The face plane is generally weakly expressed, but for the longwall it acquires important significance, since it almost coincides with the plane of the breast of the face. Because the face plane is expressed comparatively weakly, it does not in itself cause accidental cleavage of the coal, but only facilitates the leveling of the face.

The leading role in the cleavage of the coal belongs to exoplane I-a in combination with the bedding and the main plane. Plane I-a is very well expressed here. It cuts the breast of the face at an acute angle equal to 20°, as a result of which it is exposed over large areas.

Along these planes large blocks of coal cleave off; moreover, because exoplane I-a dips toward the roof of the seam, the block cleaved along it is easily separated from the bedding as from a plane overhanging the worked-out space, and then rapidly slides down along plane I-a, sometimes knocking out the support on its way.

The most dangerous cleavage of coal along these planes occurs after blasting, when, owing to the shock, coal separates in large masses along exoplane I-a and overhangs the worked-out space. Often a slight blow with a pick is enough for the enormous block, having separated from the face, to slide down rapidly. It is necessary every time after blasting to clean down the face carefully, especially in those places where exoplane I-a is exposed.

Exoplane I-bis, as we have already noted above, has no substantial significance in the cleavage of the coal, since it cuts the breast of the face at an angle of 75°; but it considerably facilitates cleavage along the bedding, for this plane is close to the latter.

b) Longwall No. 2. Observation point 27. Movement of the face from north to south.

Here it is necessary to note that near this longwall, 25 m to the north, several domes were recorded, owing to which

it was necessary to abandon the longwall that had been started and to leave a small pillar. The conditions under which these domes formed remained unknown, since no observations were made there during the work, and later it was impossible to penetrate there.

In this working we observed the same planes, with the same elements of occurrence, with the exception of joint plane 1-bis, which came still closer to the bedding and practically merged with it.

The intensity of coal cleavage in this longwall is considerably less than in longwall No. 1, since in longwall No. 1 joint plane 1-a is inclined toward the face and is turned somewhat toward the roof of the seam; therefore the coal, having separated along this plane, easily slides along it and along the bedding plane. In longwall No. 2 it is inclined away from the face and turned somewhat toward the floor of the seam, as a result of which the coal that has separated along it lies upon the bedding plane and is thus pressed against the floor.

This circumstance compels us to conclude that the direction of advance of the longwall along the strike will be more advantageous from north to south than from south to north.

5th Wing

On the 5th wing, seam III Internal is being worked by a longwall (observation point 29). The extraction working is located 210 m north of the main crosscut of the mine. The longwall advances from north to south.

The drift along seam III Internal north of the main crosscut encountered only two transverse disturbances, of the type of a normal upthrow, each with a horizontal amplitude of up to 10 m. These disturbances were encountered near the main crosscut of the mine and are located: the first 130 m, and the second 170 m south of the place where the longwall was laid out. Thus these disturbances, being remote from the longwall, could not have had any substantial influence on the section of the seam directly adjoining the longwall.

The normal thickness of the seam varies within the limits of 4.5–5 m; however, in this longwall a small squeezing of the seam was found, where its thickness decreased to 3.9 m. The roof of the seam is represented by strong sandy shales penetrated by thin streaks of bright coal. In places the sandy shale separates from the roof in large slabs with an area of 1–4 sq. m. The floor of the seam is represented by dark-gray strong argillite. The floor is uneven. Benches 0.25–0.30 m high are clearly visible; their formation was caused by the squeezing of the seam. In the coal seam there is a small interbed of argillite 1.2 m from the floor of the seam. In the floor of the seam there is a bench of strongly crushed coal 1.4 m thick. In this bench dripping water is observed, which, by washing out the coal, promotes its falling out; at the same time the coal crumbles into fines. Above this bench the coal is strong, but with well-expressed ...

by cleavage planes. At the very roof there is an interlayer of soft coal, \(0.10\)—\(0.15\) m thick.

The following planes were observed here.

Table 12.

Bedding	Bedding	Endoplanes	Endoplanes	Endoplanes	Endoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes
Bedding	Bedding	Main	Main	Face	Face	I-a	I-a	II-a	II-a	III-bis	III-bis
Az.	dip angle	Az.	dip angle	Az.	dip angle	Az.	dip angle	Az.	dip angle	Az.	dip angle
42	66	237	49	152	77	178	68	86	42	4	52

All these planes influence the spalling of the coal in two combinations; in both combinations the controlling role belongs to exoplane III-bis. Dipping toward the face, this plane is oriented in the seam in such a way that it also dips toward the roof of the seam, as a result of which a piece of coal that has separated along it is easily detached from the face wall.

The first combination—the main plane, the face plane, exoplane III-bis, and exoplane II-a.

All these planes, except the face plane, are rather distinctly expressed in the coal seam. The face plane influences the spalling of the coal insofar as it coincides with the breast plane of the longwall face.

Exoplane III-bis and exoplane II-a, intersecting in the coal seam, form a dihedral angle. The line of their intersection dips eastward somewhat more gently than the dip of the seam. A piece of coal that has separated upward along the main plane falls out of this dihedral angle; in doing so it is easily torn away from exoplane II-a, as from a plane overhanging the worked-out space, and then rapidly slides along exoplane III-bis. Sometimes the piece of coal below separates along the main plane, but then it merely settles and remains in place.

The shape of the piece obtained when the coal spalls along these planes is an elongated triangular prism, bounded by the face plane, exoplane II-a, or the main plane, and exoplane III-bis.

The second combination—bedding, exoplane I-a, and exoplane III-bis.

Spalling of the coal along these planes is especially well manifested in the near-roof part of the seam. A piece of coal, having easily separated from exoplane I-a and the bedding, slides along exo—III-bis as along a steep inclined plane. As is clear from this description, moving the longwall face from north to south in the 5th wing does not have the advantages that were established for the 4th wing. But in general, both in the former and in the latter case, mining the seam in a layer \(3.5\)—\(4\) m thick caused no special complications.

Manifestation of Cleavage Planes in the Gorely Seam.

(Observation points 20, 21, 22, 23, 24, and 26).

In the Gorely seam at the Koksovaya Mine, wings 4 and 5 have no stoping operations; therefore, we had to make observations of cleavage only in development workings, which, incidentally, are only in an embryonic state, especially on wing 5, where a drift only 100 m long has been driven south from the main crosscut.

We made our principal observations of the Gorely seam on wing 4—south, where we succeeded in investigating six points.

The Gorely seam on wing 4—south occurs under conditions of normal bedding. The drift driven along this seam from the main crosscut to the south, and from the southern intermediate crosscut to the south and north, encountered no disturbances.

The normal thickness of the seam, equal to 9.5 m, is well maintained along the strike. The roof of the seam is represented first by argillite, 5 m thick, and then by sandstone. The floor of the seam is represented first by carbonaceous shale, and then also by sandstone.

In the roof of the seam there is an interbed of clay shale, penetrated by thin stringers of coal, 0.25 m thick. Below this interbed there is a second interbed of clay shale, 0.1–0.15 m thick, and, finally, in the middle of the seam there occur small lenses of oolitic iron ore, 0.1–0.15 m thick. In the floor of the seam there is a band of crushed coal 0.6 m thick.

In the coal seam we observed the following planes.

Table 13.

Bedding	Bedding	Endoplanes: Principal	Endoplanes: Principal	Endoplanes: Face	Endoplanes: Face	Exoplanes: I-a	Exoplanes: I-a	Exoplanes: III-bis	Exoplanes: III-bis
255	62	52	30	165	75	230	68	18	68

All the planes, with the exception of the face plane, are very well expressed. On the bedding and principal planes, slickensides and striations are often visible. The influence of these planes on the splitting of the coal will depend on the orientation and direction of the stoping working. In the development workings we observed splitting of the coal chiefly along the bedding, the principal plane, and exoplane I-a.

Mine 3—3-bis.

At the time of observation, stoping operations in mine 3—3 bis were concentrated in two places: on the eastern wing of syncline 6, which corresponds to wing 4 of the Koksovaya Mine, being its direct continuation to the south, and on the western wing of syncline 5, which corresponds to the first wing of the same mine.

On the eastern limb of syncline 6, seams IV and III Internal were worked: in IV Internal, by a system of diagonal slices with cutting into long pillars along the strike; and in III, by inclined slices, with the seam divided into 2 layers and extracted in ascending order by a solid face (longwall). In the second place, only the Gorely seam was worked; here, over a comparatively small section of it, 600 m in length, three different systems were applied: 1) a system of inclined slices, with the seam divided into three layers and extracted in ascending order, each layer by a solid face; 2) a “zone” system, in which the seam is divided into short pillars and they are extracted by horizontal layers in ascending order, and within the layer by narrow strips across the strike; 3) a system of horizontal layers, extracted in descending order. It is clear that the greatest interest for us was presented precisely by this latter sector, where we were able to observe the manifestation of cleavage planes in one and the same seam under three different systems of working, concentrated practically at one point. But, in order not to range too widely, we shall present the results of our observations in the order indicated above.

1. System of diagonal slices. Seam IV Internal.

(Observation point 17).

This system at mine 3–3 bis was observed by us in seam IV Internal on the eastern limb of syncline 6, 350 m south of the mine’s main crosscut. The azimuth of dip of the seam is 253°, angle 65°. The chute dips north at an angle of 35–40°. The main drift, 410 m long, at the adit level encountered only one disturbance, with dip azimuth 124°, angle 60°, 60 m south of the place where the stoping working was laid out; it was of the type of a conformable upthrow, with a rather considerable horizontal amplitude.

The normal thickness of the seam in this sector ranges from 7.57 to 8.27 m. The roof of the seam is represented by a weakly stable sandy-clayey argillite. The floor is sandy argillite.

At the roof of the seam the coal is fairly strong. There are two rock partings. The first parting is graphitic argillite, 0.10 m thick, at a distance of 0.7 m from the roof of the seam. Below it there is a second parting of sandy argillite, 0.07–0.10 m thick. In the floor of the seam the coal is weaker, in places strongly crushed.

The following planes were observed here.

Table 14.

Bedding	Bedding	Endoplanes: main	Endoplanes: main	Endoplanes: end	Endoplanes: end	Exoplanes: I-a	Exoplanes: I-a	Exoplanes: I-bis	Exoplanes: I-bis	Exoplanes: II-a	Exoplanes: II-a
253	65	45	20	155	71	194	78	333	35	125	78

All the cleavage planes in the seam are manifested very distinctly. Of the exoplanes, I-bis and Ia are especially pronounced. The leading role in delamination belongs to exoplane I-bis, since here, as on the northern slopes at the Koksovaya mine, it cuts the roof at an acute angle. Exoplane II-a, although also well manifested, plays an insignificant role in the delamination of the coal.

All these planes affect the delamination of coal in two combinations.

The first combination is bedding, the principal plane, and the end plane.

The influence of this combination of planes in analogous workings at the Koksovaya mine has already been described. Due to the delamination of the coal along these planes, overhangs are observed in the course of the work.

The second combination is exoplane I-bis, exoplane I-a, sometimes replaced by the end plane, and bedding.

This combination of planes creates hazardous delamination of the coal, with exoplane I-bis playing the leading role. Large blocks of coal delaminate along this plane. Thus, at the time of observation, in the upper part of the working, along the planes of this combination and especially along exoplane I-bis, a large dome had formed, 2 m high and 3.5 m long across the strike of the seam. Such delamination of coal in this working is a common occurrence, and in terms of its accident hazard it is no different from workings of this system at the Koksovaya mine.

2. System of inclined slices. Seam III Vnutrennii.

(Observation point 18).

Inclined slices on the eastern limb of syncline 6 are used in Seam III Vnutrennii. The stoping face is located 50 m from the main crosscut of the mine. The seam is worked in two slices in ascending order. The thickness of the lower slice is 2.60 m, and of the upper slice, 2.80 m. There is no natural boundary between the slices. The faces are staggered by 5–10 m. Extraction of the seam is carried out in strips from top to bottom. The width of a strip is 1.20 m.

The seam occurs in a rather complex tectonic setting. Several disturbances have been recorded here: one at the end of the drift, 530 m from the main crosscut, with dip azimuths of 182°, ∠65°; the second, 370 m from the main crosscut, with dip azimuth 120°, ∠65°. At 95 m south of the latter disturbance, two more disturbances were encountered, with dip azimuths of 305° and 205° and dip angles of 40° and 75°, respectively. All these disturbances had a great influence on the coal seam.

The normal thickness of the seam varies within the range 4.5–5.5 m; the dip azimuth is 255–64°. The roof and floor of the seam are fairly stable argillite.

There are two rock partings in the coal seam. The first parting, occurring at the roof of the seam, is a graphitoid argillite, 0.10 m thick. The second parting is a carbonaceous argillite, 0.20–0.25 m thick, 1 m from the roof of the seam.

Here we observed the following planes.

Table 15.

Bedding	Bedding	Endoplanes	Endoplanes	Endoplanes	Endoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes
Az.	ang.	Main: Az.	Main: ang.	Face: Az.	Face: ang.	I-a: Az.	I-a: ang.	I-bis: Az.	I-bis: ang.	II-a: Az.	II-a: ang.
255	64	47	28	150	87	195	69	329	35	125	81

The complexity of the tectonic setting strongly affected the cleavage lattice of the seam. All the cleavage planes are exceptionally sharply expressed. The main plane and the bedding are covered with slickensides and striations.

We observed coal spalling only in the lower layer. Here the chief role was played by exoplane I-a, which produces boat-shaped separateness, since the surface of this fracture is strongly undulating. In addition to this plane, the coal also splits well along the bedding, the main plane, and partly along exoplane I-bis.

The most intense spalling along these planes occurs from the side of the face. Exoplane I-a cuts the face at an acute angle. At the top the coal splits along the main plane, at the sides along the bedding, and then easily slips along exoplane I-a, as along a steeply inclined plane dipping toward the face.

As for the roof of the working, it proved stable, since all the cleavage planes cut it at considerable angles.

At the time of observation we did not observe hazardous spalling; evidently, this must be explained by the stable roof of the working.

Experimental section of the Gorely seam.

The Gorely seam, as already indicated above, was worked by three different systems. The northern part of the seam was worked in zones, the middle part by inclined layers, and the southern part by horizontal layers. Correspondingly, the seam was divided by preparatory workings into three approximately equal parts.

The experimental section was chosen rather successfully in terms of geological conditions, since along the Gorely seam the drift driven...

at a distance of 600 m from the main crosscut of mine 3—3-bis, did not encounter a single noticeable disturbance¹.

The normal thickness of the seam is 9.0 m; it is well maintained both down the dip and along the strike. The roof of the seam is represented by weakly stable argillite. The floor of the seam is represented at first by clay shale penetrated by streaks of coal, and then by sandy argillite, on the whole fairly stable.

The coal seam is comparatively clean and only in places contains lenses of oolitic ironstone. In the northern part of the seam, 6 m from the floor, there occurs a thin interbed of light-colored fine-grained sandstone, 0.02–0.05 m thick.

In the roof the coal is comparatively strong; in the floor of the seam it is usually crushed, strongly fissured, and bears abundant traces of rubbing along cleavage planes.

Above the —265 horizon the coal seam has burned out. The pressure of these burnouts is of great importance in mining the upper horizons of the seam.

The following planes were encountered in the Gorely seam (Fig. 28).

Table 16.

Bedding	Bedding	Endoplanes	Endoplanes	Endoplanes	Endoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes	Exoplanes
Az.	angle	Main Az.	Main angle	Face Az.	Face angle	I-a Az.	I-a angle	I-bis Az.	I-bis angle	II-a Az.	II-a angle	II-bis Az.	II-bis angle	III-a Az.	III-a angle
51	48	247	46	150	79	191	80	332	41	104	75	52	67	266	70

1. Inclined layers.

(Observation points 1, 2, 4).

The Gorely seam was mined in three layers, each 3 m of normal thickness. Two layers were in operation at the same time: one was being extracted, and the other was being packed. The advance of one layer relative to the other was 15 m along the strike. The layers were extracted in strips elongated down the dip of the seam, 1.2 m wide and as long as the full height of the level, 4.7 m. Extraction of the strip proceeded from bottom to top. In the first layer, the floor of the working was the floor of the seam, and the roof was coal. In the second layer, the floor of the working was packing material, and the roof of the working was coal. In the third layer, the floor of the working was packing material, while the roof of the working was partly the roof of the seam and partly coal, which in places was left in the roof in order to protect it from doming.

Cleavage planes affect the splitting of the coal in several combinations, and each combination is confined to a definite layer.

In the first layer the coal splits along exoplane II-bis, the principal plane, exoplane III-a, and the face. The guiding role in splitting belongs to exoplane II-bis, which is close to the bedding; dipping conformably with the seam, it cuts the roof of the working at an acute angle, causing constant sagging of the roof.

In the second layer the coal is softer and more strongly fissured. Here almost all cleavage planes are observed; however, the coal splits most readily along the principal plane, exoplane II-bis, and exoplane I-bis. Here, too, the guiding role in splitting belongs to exoplane II-bis, along which the coal, as along a steep overhanging plane, easily separates. At the sides, however, the coal splits along exoplane I-bis and slips along the principal plane.

In the third layer two combinations of planes influence the splitting of the coal.

First combination—exoplane II-bis, the principal plane, and the face.

At the moment of observation this combination of planes was better manifested at the top of the working. The effect of this combination is the same as in the first layer. Here, however, this combination already represents a considerably greater danger, since the roof of the seam is weak and, together with the coal, more or less substantial falls of it occur. Therefore, when mining the third layer, they try not to expose the roof, leaving a little coal in the roof.

Second combination—exoplane II-bis, I-a, and II-a.

This combination is better manifested at the base of the layer. Here a piece of coal, having split off along exoplanes I-a and II-a, whose line of intersection dips rather steeply from the roof toward the worked-out space, easily slips along exoplane II-bis.

When the roof caves, it yields large pieces, 1.2 m long and 0.2 × 0.5 m in cross-section. The coal does not yield large pieces, although substantial masses of it split off, because, cut by a large number of differently oriented fractures, it crumbles into small pieces when it falls. The largest pieces of coal do not exceed 0.3 m. We did not observe any accidents in the mining of this system.

3. Horizontal layers. Extraction in descending order.

In this system the coal is extracted in layers in descending order, with complete stowing of the extracted layer, the height of which is 2.4 m. The layers are extracted in strips 20–27 m wide, in the direction from the roof to the floor. To prevent the stowing material from spilling down from above onto the floor of the extracted ...

a lagging is laid. Thus the roof of the working is a wooden lagging, on which the packing material rests, while the floor of the working is coal.

With this method of working, overhanging coal is completely eliminated, and the lateral pressure, when coal is extracted in strips from the roof toward the floor, is of no importance; therefore the cleavage planes of coal separation do not cause harm and only facilitate its breaking during extraction.

Zone system.

(Observation points 7, 6, and 23).

When working by the zone system, the story, whose vertical height is approximately 40 meters, is divided into two substories, leaving between them a protective pillar 3–4 m high. Before extraction, each substory along the strike is divided into 10 m intervals—“zones”; in the intervals between them protective pillars 3–4 m thick must also be left. Coal extraction begins from the upper substory and is carried out in horizontal layers 2.2 m high in ascending order, the zones being extracted successively one after another. The work is conducted using special bench timbering and with complete packing of the worked-out space; without packing, extraction of no more than two layers is permitted. Thus the roof of the working is always coal, and the floor is the wooden lagging of the preceding layer.

Observations of cleavage were carried out in the lower and upper substories of zone No. 4 and in the upper substory of zone No. 3.

The cleavage planes manifest themselves differently in different parts of the seam. In the weaker parts of the seam, especially near the floor, almost all exoplanes are expressed with equal distinctness, with the exception of exo-II-a, which was recorded only in the lower substory of zone No. 4 and in the upper one—of zone No. 3. Closer to the roof the fracturing of the coal is manifested more weakly, but here too the exoplanes II-bis, I-a, and I-bis are quite clearly expressed. The bedding and the principal plane are likewise always distinctly expressed and play a very substantial role in the separation of the coal, although at times they are also replaced respectively by the exoplanes II-bis and III-a.

According to our observations, these planes influence the separation of the coal predominantly in the following combinations.

First combination—principal, II-a, I-a, and II-bis or bedding.

This combination creates accidental separation of coal at the floor of the seam in the lower substory of zone No. 4. The leading role here belongs to exoplane II-a and to the principal plane. Here we obـ

observed how, along these planes, a dome 5 m high formed. The coal at the top split off along the main plane and partly along exo-III-a, at the sides along exoplanes II-a and I-a, and then slipped along the bedding (Fig. 29).

The second combination—exoplanes III-a, I-bis and II-bis, or bedding.

This combination is more often observed in the roof of the seam. Here the coal at the top splits off along exoplane III-a¹, and from the sides along the bedding and exoplanes II-bis and I-bis. The pieces that split off usually have the form of irregular rhombohedra.

As is evident from this description, the zone system has no advantages whatever in comparison with other systems. Because of the narrow working front, it is less productive than the systems of inclined and diagonal slices, and at the same time it has the disadvantages inherent in these systems, both because of the overhanging coal above one’s head and because of its destruction in the roof zone when being undercut from below. By the very nature of the work it requires special support (stand support) and, despite the use of this complex and expensive support and the extraction of coal in narrow strips, it does not prevent sudden emergency falls of coal from the overhanging roof of the working. These falls of coal greatly hamper the work and constantly threaten accidents. During our observations there were several cases in which work was stopped for this reason.

Conclusion.

We are not specialists in the field of deposit exploitation. Therefore, a comprehensive assessment and selection of one or another system of mining for the seams we investigated was not and could not be part of the task of our work. Nevertheless, the observations we carried out—although short-term, but more or less systematic—in the stoping faces of various mining systems make it possible to draw certain comparisons and conclusions, which will probably be of some interest to specialists when deciding this question.

In mining the thick seams of the Prokopyevsk district of Kuzbass, several different systems are used, representing certain modifications of all types of slice mining.

A. Diagonal slices in several variants.

1) The normal system of diagonal slices, with advancement of the diagonal face along the strike (seam IV, Internal 4 of the wing—north of the Koksovaya Mine, and the eastern wing of syncline 6 of Mines 3 and 3-bis).

2) The so-called single-slope system, or the system

diagonal layers along the raise, representing another variant of the same system of diagonal layers, but in this case the extraction of the diagonal layers is carried out in ascending order and, consequently, the diagonal face advances from below upward (seam IV of the Internal Mine, Koksovaya, wings 4 and 5).

3) Finally, essentially the same system, but only with two-sided diagonal layers, which received the local name “herringbone” (Koksovaya Mine, seam IV Internal, wing 4).

B. Inclined layers with coal extraction in ascending order.

(Seams Gorely and III Internal of mines 3 and 3 bis).

C. Horizontal layers in two variants.

1) The so-called “zone,” i.e., a system in which preparation is carried out by short pillars, while extraction is conducted by horizontal layers in ascending order.

2) Horizontal layers extracted in descending order (both of the latter systems on the Gorely seam—experimental section of mines 3 and 3 bis).

In addition, in some places on the III Internal seam the “longwall floor” system is used, i.e., development of the seam by a continuous face along the strike. But since, under this system, it is technically impossible to extract a seam more than 3.5–4 m thick, it ultimately amounts to extracting only one inclined layer, with coal left in the ribs in layers up to 2–2.5 m, and is in general a predatory system; for this reason we exclude it from consideration¹.

Coal splitting along cleavage planes in stoping workings is influenced, first of all, by the following circumstances.

1. The number of exposed coal planes overhanging the worked-out space.

2. The size of these exposed planes.

3. The length of the time interval during which the given plane remains exposed.

4. The orientation of the exposed planes with respect to the most important cleavage planes.

If from this point of view we examine the mining systems employed, we must come to the conclusion that such systems as diagonal layers—especially when applied to the extraction of long pillars along the rise, i.e., the single-slope system and the herringbone—are in less favorable conditions in comparison with other systems. Their principal disadvantages are the following.

1. An abundance of exposed planes, namely: a) the roof of the working, which is also the boundary of the diagonal layer; b) the side of the working or

the upper cut of the seam; (c) the side of the strip and (d) the face of the strip; moreover, in the “herringbone” system their number increases further because of the other incline and the cutting of the ridge at the intersection of both inclines.

1. A large part of these planes overhangs the worked-out space, naturally threatening collapses of the coal that has cleaved along them. This danger is further aggravated by the circumstance that blasting operations are usually used in breaking the coal; these cause shaking in the mass of coal hanging overhead, promote the opening of cleavage cracks, and weaken cohesion along them.

2. The boundary of the seam being extracted, which forms the inclined roof of the working, is an enormous area that remains exposed, unsupported during extraction of the entire seam; this promotes the sloughing of the coal, i.e., its natural cracking under the action of its own weight and the pressure of the overlying rocks.

3. A very substantial shortcoming of these systems is also the relatively slow advance of the stoping workings. With normal operation, a pillar measuring 30 m along the strike and 35–40 m along the rise should, according to estimates, be extracted within 4–6 months. According to the mine-surveying plans, however, it is evident that in fact its extraction continues for 8–10 months, and sometimes is prolonged even up to a year. (For example, the herringbone on seam IV Internal, 4th wing south.) Consequently, during all this time the mass of coal located above the worked-out space is subjected to the systematic action of shocks from explosions, the pressure of the roof, etc.; as a result, in the end it cracks, turning into a heap of fragments that have lost their connection with one another and with the surrounding rocks. It is clear that under such conditions the working of a pillar, especially in its final stage, becomes extremely difficult and dangerous.

If to this we add the absence of a rigid support at the timbering that holds up the roof of the working—not to mention the untimely and incomplete packing of the worked-out space, which is observed quite often at the mine—then it becomes clear that it is, at the very least, difficult to recommend these systems, especially for working such fissured seams as IV Internal and Gorely.

In essence, the same shortcomings are also characteristic of the system of diagonal slices in its pure form, i.e., with the stoping face moving along the strike of the seam. The advantage of this system, in comparison with the preceding ones, consists only in the fact that here, as the face advances, ever new thicknesses of coal are exposed in the roof. Therefore the effect of shocks during blasting should have less impact on the roof thickness. In addition, here there is the possibility of choosing the direction of face advance—along the strike in one direction or the other—which, with a certain arrangement of the cleavage lattice, is sometimes of substantial importance.

However, the other shortcomings inherent in diagonal layers—namely, the presence of large exposed planes overhanging the worked-out space, the abundance of exposed planes overhead, and the slow advance of the face—are fully retained here as well. In general, the slight advantages of this system are obscured by these basic shortcomings, and therefore the rationality of its application, especially in highly fractured seams, must likewise be called into question. All the more so because, in those places where we were able to observe it—namely, along IV Inner of the 4th wing—north in the Koksovaya mine and on the eastern limb of the 6th syncline of mine 3–3 bis—it had no advantages and was accompanied by constant accidents.

From this we draw the following conclusions:

1. The system of diagonal layers with extraction along the strike has certain advantages over the system of diagonal layers along the rise (single-slope face), but these advantages are small.

2. The shortcomings inherent in the system of diagonal layers are especially strongly felt in the working of fractured seams. Therefore, the rationality of using this system at all for the working of highly fractured seams, such as IV Inner and Gorely, is doubtful. But with stronger coals, as in seam III Inner, it may be used and could yield more satisfactory results.

However, in this connection the following circumstances must also be borne in mind.

Diagonal layers inclined to the north are in extremely unfavorable conditions, owing to the presence of the cleavage plane exo-I-bis, which cuts the plane of the diagonal face at an acute angle. As already indicated above, along this plane, in combination with the bedding and the principal plane, intensive coal separation occurs in large blocks, accompanied by accidents and even casualties. This causes frequent stoppages, and sometimes a complete cessation of work.

Diagonal layers (or slopes) inclined to the south are in somewhat better conditions. However, here too falls of large blocks and the formation of domes are often observed; in this case the dominant role belongs to the exoplane 1–a. Although it cuts the roof of the working at a less acute angle, nevertheless, being more clearly expressed, in combination with an equally clearly expressed bedding and principal plane, it creates favorable conditions for doming. Because of this, the southern slopes at some points, in terms of the intensity of separation, differ little from the northern ones.

Thus, for example, in seam IV Inner of the 4th wing—north, owing on the one hand to the proximity of the fold hinge and on the other to the disturbance passing here, the coal proved to be so broken up that its extraction encountered very serious difficulties,

despite the chosen dip of the strata to the south, work in the lower sublevel even had to be stopped.

On the other hand, in certain parts of the seams, owing to the flattening of exoplane 1-a to 50–60°, with its general dip to the south, the latter will have, for the southern slopes, the same significance as exo-1-bis has for the northern ones. This is precisely the situation we shall apparently have for the III and IV Internal seams of the 5th wing of the Koksovaya mine and for the Moshchnyi seam of mine 3 and 3-bis. This circumstance, among others, was overlooked by geologist V. A. Azimov (1), who, when recommending that in the development of the IV Internal seam in the 5th wing the inclination of the slope be changed from north to south, sought to avoid the influence of exoplane 1-bis.

Thus, the application of the system of diagonal slices, in addition to the general disadvantages inherent in it, is in our case further limited by the unfavorable position of the first pair of the most clearly expressed exogenous cleavage cracks.

That is why it seems to us that the enthusiasm of some workers of the Stalugol trust for this system must be considered erroneous.

Let us now turn to inclined slices. Inclined slices in the Prokopyevsk district of Kuzbass are still an undeveloped system, and its application under the conditions of steeply dipping seams has not yet passed beyond the experimental stage. This is probably explained by the fact that, in the opinion of leading authorities¹, this system is not generally recommended for the working of steeply dipping seams with dip angles greater than 40–45°.

However, the experience of applying it in working the Gorely seam at the experimental section of mine 3 and 3-bis (western wing of the 5th syncline), where the seam dips at 50°, and in the III Internal seam of the eastern wing of the 6th syncline, where the angle of dip of the seam reaches as much as 65°, gives, on the whole, very good results. This allows one to think that the system of inclined slices deserves more attention than has been given to it up to the present, and may find fairly broad application in the working of thick seams in the district.

Indeed, the seams we have studied in most cases have a dip within the range of 50–60°, i.e., in any case close to that of the Gorely seam in the experimental section. The only exceptions are the IV Internal seams in the southern part of the 5th wing and the Gorely seam in the southern part of the 4th wing of the Koksovaya mine, where their dip reaches 70°.

The development of each slice may be carried out by a longwall, and extraction of the slices is performed in ascending or descending order. In all cases the face line will constitute a vertical plane not overhanging the worked-out space. By orienting the cleavage planes in such a face, we

¹ See, for example, L. D. Shevyakov, Development of Seam Deposits. — Gonti, 1936, pp. 345–365.

observed in many cases in the Gorely and III Vnutrenny seams, including during the mining of the latter by a “lava.” The stability of the face in this case is, of course, much higher than with an overhanging plane of the diagonal layer. The most unfavorable are cleavage planes that cut the plane of the face at acute angles and dip toward the face, i.e., toward the worked-out space, since along them delamination and falling of the coal occur most easily. Therefore, when choosing the direction of the face, this circumstance must be taken into account.

The plane of the face in this case usually coincides, or almost coincides, with the end face. But the end face is usually weakly expressed and does not affect the spalling of the coal. Its presence merely facilitates the breaking of the coal and the straightening of the face. Of much greater importance will undoubtedly be exo 1-a plane. In places it has a steep dip and usually dips to the south. Therefore, movement of the face from south to north is generally more dangerous than movement from north to south. Especially dangerous should be considered such a position of this plane when its dip is directed both toward the face and toward the roof of the seam, since with such an arrangement of the planes sudden collapses of large blocks of coal are possible, which, with a steep dip of the seam, may cause serious consequences.

When inclined beds are mined in an ascending order (as is currently practiced), the most dangerous is the exposure of the roof of the bed, which coincides with the bedding plane. It is clear that here, too, the greatest influence on delamination of the coal will be exerted by those cleavage planes that cut the roof at an acute angle.

If, from this point of view, we analyze the cleavage grid, we obtain the following table.

Table 17.

Magnitudes of the dihedral angles formed by exogenous cleavage planes with the bedding plane.

Names of seams	Dip angle of the seam	I-a	I-bis	II-a	II-bis	III-bis
Mine named after Comrade Stalin
IV Vnutrenny—4 north wing	50	60	52	40	—	—
IV Vnutrenny—4 south wing	50	56	52	61	—	—
Gorely—4 south wing	70	22	62	—	—	—
III Vnutrenny—4 north wing	50	64	—	—	—	—
III Vnutrenny—4 south wing	60	67	30	—	—	—
IV Vnutrenny—5 north wing	60	72	40	—	—	—
IV Vnutrenny—5 south wing	69	88	50	60	—	—
III Vnutrenny—5 north wing	66	60	—	42	—	34
Mine 3-3 bis.
Gorely, west 5 syncline	50	60	54	54	25	-
Moshchny, west 5 syncline	36	84	40	54	—	—
IV Vnutrenny east 6 syncline	65	64	68	64	—	—
III Vnutrenny east 6 syncline	65	58	60	56	—	—

Endogenous planes have not been included in the table, since they form right angles with the bedding plane.

As can be seen from this table, the overwhelming majority of planes make angles of not less than 30° with the bedding. The only exceptions are seam Gorely 4 of the southern wing of the Koksovaya Mine, and the western wing of 5 of the syncline of Mines 3 and 3-bis, where in the first case exoplane 1-a intersects the bedding at an angle of 22°, and in the second, exo-II-bis at an angle of 25°. It must be noted here that in the first case the Gorely seam dips at 70°, so that the use of inclined layers there is hardly possible at all; in the second case, however, it is precisely in this area that experimental mining by the system under consideration is being carried out and, as was already indicated above, not without success.

Proceeding from these considerations, we believe that experimentation with the application of this system should be expanded, and first of all it should be tried on seams III and, perhaps, even IV Vnutrennie, which have a roof that is considerably more stable than that of Gorely.

System of Horizontal Layers

Of these systems we had the opportunity to observe two varieties—the “zone” system and horizontal layers with extraction in descending order—both in the experimental section of Mines 3 and 3-bis.

In mining by zones, the coal is developed in short pillars—zones—while extraction is by horizontal layers in ascending order; moreover, the extraction of each layer is carried out in narrow strips from the floor to the roof.

As can be seen, this system has almost all the same shortcomings that we noted with respect to the systems of diagonal layers along the rise (overhanging of coal overhead and its destruction in the roof mass), although the number of exposed planes is smaller here, and only two overhang above the working. But this system requires special and, consequently, more expensive timbering (bench timbering) and, despite this, does not prevent accidental falls of coal.

On the other hand, because of the need to leave protective pillars both between sublevels and between zones, it leads to large losses of coal, reaching up to 45%, not counting the inevitable losses from coal spilling through the plank floor separating the layer being worked from the lower one, already extracted. Thus, under this mining system, at least in the form in which it is applied at the present time, only half of the total coal reserve in the seam is extracted, which is equivalent to the Gorely seam, reaching 9 m in thickness, being mined by two 2.5-meter inclined layers, while the remaining coal is discarded.

On the basis of coal losses alone, this system cannot be characterized otherwise than as predatory, differing little from the rejected—

...and recognized as harmful, the chamber-and-pillar system. But even apart from this, as our observations show, the system of zones has a number of substantial shortcomings that make it inapplicable for mining fissured seams.

An entirely different matter is presented by the system of horizontal layers with extraction of coal in descending order—at least in the sense of complete independence from the influence of cleavage cracks and the complete elimination of the danger of accidental spalling of coal. Here there are no fissured coal masses overhanging the worked-out space. The work is carried out under packing, and everything depends on the quality of the packing and support. But the support here rests on the solid foundation of coal pillars not yet touched, while the pressure of the packing on the support, at least at the time of our observations, was small and caused no complications. In any case, no special machine support is required here, as in the zones, and in general the support differed in no way from the ordinary support of stoping faces. As for the need to lag the roof in order to prevent the packing from spilling, such lagging is also required in other mining systems with packing, in particular in diagonal and inclined layers, and in zones for separating the packed space from the working space.

Unfortunately, we do not have exact data on the comparative effectiveness of this system and its technical-and-economic indicators under Kuzbass conditions, since up to now it has, for some reason, not been used there at all. Meanwhile, it would seem that it deserves special attention, since in all other respects—as regards completeness of coal extraction, fire safety, and complete independence from the degree of fissuring of the coal and the stability of the enclosing rocks—it is positively ideal.

At the experimental section of Mine 3 and 3-bis, where we had the opportunity to observe this system, coal extraction is carried out successively in narrow strips across the strike of the seam. But it is clear that some variations are possible here. In particular, some widening of the strips is probably possible, as is the creation of a stepped face, a change in the direction of the strips, and so forth, which will make it possible to expand the working front and increase face productivity.

Therefore, it seems to us that experimentation should be conducted first of all in the direction of improving and mastering this system, with the aim of introducing it for the mining of strongly fissured and broken seams that do not permit coal to be left overhead. Especially important, in our opinion, is the testing of this system for mining the sections most dangerous with respect to accidental coal spalling, such as, for example, in places of disturbances and especially at junctions of thick seams, where the use of any other system is entirely excluded.

As the experience of working the Gorely seam shows, this system can also be successfully applied to thick seams with a comparatively weak roof.

In other cases, such as, for example, on the III Inner and IV Inner seams, where it is not too fractured and has a moderate dip, as with seams having a stable roof, the system of inclined layers should be tried. As we have already noted above, the experience of applying this system on the III Inner seam gave quite good results, proving the possibility of its use also on steeply dipping seams, contrary to the opinion of some specialists. Very encouraging results were also obtained on the Gorely seam, although this seam—highly fissured in general and also compressed by the burn zones immediately above the working horizon, as well as having a weak roof and an unfavorable arrangement of cleavage planes—is not a favorable object for this system.

This, in our opinion, is the direction in which further experimental work should proceed in selecting the most rational system (or rather, systems) for mining the thick seams of the Kuzbass. But this work should not be carried out blindly, as it has been up to the present; rather, it must take into account the disposition of the cleavage planes. In other words, work on studying cleavage and its manifestations in stoping workings, and experimental work on testing one or another mining system, should be carried out in parallel and in coordination, mutually correcting and complementing one another.

Table 1

Variability of the cleavage lattice along the strike of seam IV Internal of the Koksovaya Mine named after Comrade Stalin.

Point Nos.	Bedding Az.	Bedding Angle	Main Az.	Main Angle	Face Az.	Face Angle	I-a Az.	I-a Angle	I-bis Az.	I-bis Angle	II-a Az.	II-a Angle	III-a Az.	III-a Angle	III-bis Az.	III-bis Angle
Seam IV Internal, 4th wing.
South.
12	253	60	62	36	159	75	—	—	320	38	93	60	—	—	—	—
7—10	260	60	68	35	159	72	202	75	319	50	127	74	—	—	—	—
6—9	255	60	57	43	152	72	196	75	325	27	100	58	248	74	—	—
x	253	62	32	44	158	80	193	78	313	30	100	65	—	—	—	—
8	255	64	71	27	154	76	199	56	—	—	—	—	—	—	—	—
Average values	256	61	58	37	156	75	198	71	321	38	105	64	248	74	—	—
North.
1—2	243	58	70	38	145	81	183	75	285	29	87	60	—	—	—	—
11	265	45	85	40	155	80	185	75	305	30	—	—	278	58	—	—
5	253	45	87	47	156	72	193	84	330	29	—	—	—	—	—	—
4	258	46	57	45	147	83	174	84	318	25	—	—	—	—	—	—
Average values	255	47	75	42	151	79	184	80	310	28	87	60	278	58	—	—
Seam IV Internal, 5th wing.
North.
36	42	59	258	34	168	79	210	61	330	21	110	50	—	—	—	—
35	52	65	254	26	169	85	—	—	—	—	108	48	—	—	7	37
Average values	47	62	256	30	168	82	210	61	330	21	109	49	—	—	7	37
South.
32—33	60	69	253	31	164	75	176	47	—	—	104	67	—	—	12	34
Average for the wing	51	64	255	30	167	80	193	54	330	21	107	55	—	—	10	35

Table 2.

Variability of the cleavage lattice along the strike of the seam
III Internal, Stalin Mine.

Point nos.	Bedding Az.	Bedding Angle	Main Az.	Main Angle	Face Az.	Face Angle	I-a Az.	I-a Angle	I-v Az.	I-v Angle	II-a Az.	II-a Angle	III-bis Az.	III-bis Angle
4th wing, south
18	250	54	70	44	156	82	170	84
19–27–15	265	59	50	33	161	74	187	74
17–28–16	262	63	63	30	150	70	197	62	295	51
Average values	262	59	61	36	156	75	185	73	295	51
4th wing, north
41	265	60	60	40	—	—	190	70
14	254	57	62	36	166	76	—	—
13	272	46	60	41	156	74	—	—
Average values	264	54	61	39	161	75	190	70
5th wing
31	44	67	243	31	148	77	196	67	—	—	93	45	6	65
29	42	66	237	49	152	77	178	68	—	—	86	42	4	52
30	55	66	248	22	155	84	192	66	—	—	82	46	—	—
Average values	47	66	243	34	152	79	189	67	—	—	87	45	5	58

Table 3

Variability of the cleavage lattice along the strike of the seam
Burnt, Stalin Mine.

Point nos.	Bedding Az.	Bedding Angle	Main Az.	Main Angle	Face Az.	Face Angle	I-a Az.	I-a Angle	I-v Az.	I-v Angle	II-a Az.	II-a Angle	III-bis Az.	III-bis Angle	IV Az.	IV Angle
4th wing
22	257	62	55	32	158	78
23	255	61	56	35	174	72									223	47
24–25	254	60	43	36	179	71	215	95
26	260	65	54	32	—	—	240	64
20–21	252	62	58	24	150	85	193	106
Average values	256	62	53	32	165	75	216	88							223	47
5th wing
38–39	38	71	276	60	140	55	210	100	—	—	95	52
Average values	38	71	276	60	140	55	210	100	—	—	95	52

Table 4

Variability of the cleavage grid along the strike of the seams of mine 3-3 bis.
(Observation points are located from N to S.)

Seams, observation points	Bedding Az.	Bedding Ang.	Endoplanes—Main Az.	Endoplanes—Main Ang.	Endoplanes—Face Az.	Endoplanes—Face Ang.	Exoplanes I-a Az.	Exoplanes I-a Ang.	Exoplanes I-bis Az.	Exoplanes I-bis Ang.	Exoplanes II-a Az.	Exoplanes II-a Ang.	Exoplanes II-bis Az.	Exoplanes II-bis Ang.	Exoplanes III-a Az.	Exoplanes III-a Ang.
Seam Gorelyi, western limb of the 5th syncline
Nos. 7, 6, 23 (zone)	48	50	236	56	150	86	197	81	336	33	106	73	56	68	280	70
No. 11	49	52	248	48	150	74	6	65	—	—	—	—	44	70	281	74
No. 12	60	41	245	44	160	70	12	88	336	42	—	—	46	72	270	70
Nos. 1, 2, 4 (pack layer)	51	42	246	49	150	79	194	85	330	47	105	71	50	64	274	70
No. 13	48	55	253	38	149	80	—	—	—	—	—	—	52	54	—	—
Nos. 8, 9, 3	49	46	252	44	151	85	191	82	325	43	100	81	63	74	—	—
Average values	51	48	247	46	150	79	191	80	332	41	104	75	52	67	276	71
Seam Moshchnyi, western limb of the 5th syncline
No. 24	62	35	259	44	154	78	—	—	333	18	—	—	55	58	—	—
No. 25	63	36	259	42	174	68	—	—	—	—	101	74	—	—	304	68
No. 26	53	40	257	44	161	75	197	55	—	—	106	77	—	—	299	87
Average values	57	36	258	43	159	78	197	55	333	18	104	76	55	58	302	74
Seam Vnutrennii Vost., western limb of the 6th syncline
No. 14	256	62	43	49	156	69	—	—	345	31	122	71	—	—	—	—
No. 16	253	63	58	24	155	70	187	87	335	62	125	58	—	—	—	—
No. 15	256	68	49	35	155	70	—	—	350	25	110	60	—	—	—	—
(Diagonal layer) No. 17	253	65	45	20	155	71	194	78	333	35	125	78	—	—	—	—
Average values	255	65	49	32	155	70	190	82	341	38	120	67	—	—	—	—
Seam Vnutrennii Vost., western limb of the 6th syncline
No. 18	255	64	47	28	150	87	195	69	329	35	125	81	—	—	—	—
No. 22	255	65	51	45	—	—	187	67	333	36	105	70	—	—	—	—
No. 19	260	56	32	48	149	74	190	64	325	37	125	81	—	—	—	—
No. 20	255	62	63	32	149	87	187	67	317	62	102	55	—	—	—	—
Average values	256	65	58	48	150	82	192	67	326	42	114	72	—	—	—	—
Seam Moshchnyi, eastern limb of the 6th syncline
No. 26	269	60	66	29	177	77	210	60	—	—	107	81	—	—	—	—
Average values	269	60	66	29	177	77	210	60	—	—	107	81	—	—	—	—

Table 5

Variability of the cleavage lattice along the strike of the rocks of the Stalin Mine 3 and 3-bis.

No. of observation point	Name	Bedding, Az.	Bedding, angle	Endocleat, main, Az.	Endocleat, main, angle	Endocleat, end, Az.	Endocleat, end, angle	Exocleat I-a, Az.	Exocleat I-a, angle	Exocleat I-bis, Az.	Exocleat I-bis, angle	Exocleat II-a, Az.	Exocleat II-a, angle	Exocleat III-bis, Az.	Exocleat III-bis, angle	Exocleat IV, Az.	Exocleat IV, angle
	Mine 3-bis
1	Sandstone-5 synclinal, eastern wing of seam IV Internal, 20–40 m from the projection of the main crosscut onto the surface	250	65	64	19	161	85	—	—	336	35	77	81	—	248	35	—
2	Sandstone—exposure on top of mine 3-bis, 57 m from the syncline	57	36	225	38	151	80	170	70	327	47	—	—	—	—	—	—
3	Sandstone-5 synclinal, eastern wing, 10–15 m from the roof of seam Powerful	270	70	73	22	167	80	—	—	—	—	—	—	30	71	—	—
4	Sandstone-5 synclinal, eastern wing, from the projection of the main IV Internal crosscut to the surface, 50–80 m, and from the roof of III 20–30 m	250	70	65	22	155	80	—	—	—	—	89	73	12	57	—	—
	Mine named after Comrade Stalin
1	Sandstone-2 circular, 300–400 m from the projection of the main crosscut onto the surface between seams III and IV Internal, and also seams Powerful and Burnt	238	67	62	20	148	86	—	—	—	—	117	56	—	—	—	—
2	Sandstone-6 circular, 200–300 m from the projection of the horizontal crosscut onto the surface, in the roof of seam IV Internal	275	60	92	26	182	88	—	—	344	27	—	—	—	—	—	—
3	Sandy shales-2, north wing, 400–500 m from the projection of the adit onto the surface	258	53	69	42	164	78	—	—	—	—	—	—	9	57	—	—
4	Sandy shales-1 wing to north, 350–400 m from the projection of the adit onto the surface	65	61	241	25	172	78	—	—	—	—	107	81	—	—	—	—

List of References

1. Azimov, V. A.—On cleavages in the coal seams of the Koksovaya Mine named after Stalin, of the Stalinugol Trust, Kuzbass Combine. Brief report on observations made of cleavage behavior in stopes in 1938. Manuscript in the files of the Mine Administration.

2. Belov, V. I.—Fracturing in coal and rocks from the standpoint of rock-mass mechanics in coal mining.—Collection of materials on roof-control management. ONTI, 1936.

3. Lise, Ch. K.—Structural Geology. ONTI. M.–L., 1935.

4. Ivanov, G. A.—Jointing (cleavage) in coals and associated rocks of the Donets and Moscow Basin, their origin and use in Stakhanovite methods of work.—Lithographed edition of TsNIGRI. Mineral Raw Materials Sector. L., 1936, 228 pp. Bibliography of 65 titles, with numerous figures, photographs, and drawings.

5. Yete, V. S.—Cleavage and other microscopic features of seams prone to sudden gas outbursts.—Journal Safety of Labor, 1935.

6. Naidysh, A. M.—Roof control on the Smolyaninovsky seam of Mine No. 6 “Krasnaya Zvezda,” Budennovsky Mine Administration.—Collection of materials on questions of roof control. ONTI, 1935.

7. Ende, K.—Die Bildung von Schlechten und Drucklager in Steinkohlenflotzen.—Glückauf No. 48–49, 1929.

8. Faulkner and Phillips.—Cleavage, induced by Mining.—Trans. of the Instit. of Mining Eng., vol. LXXXIX, 1935.

9. Leith, C. K.—Rockcleavage.—USGS Bull. 203, 1905.

10. Oberste, Brink u. Heine.—Klüfte und Schlechten in ihren Beziehungen zum geologischen Aufbau des Ruhrkohlenbeckens.—Glückauf, No. 43, 1934.

Fig. 1-a

Program 193

Cleavage

Mine ______

Seam ______

____ wing of the ______ syncline

(name of working)

____ m ___ from picket No. ___

Horizon _________

Coordinates: \(x =\) ____

\(y =\) ____

\(z =\) ____

Observer, ________

Sketch of the sample

Sketch of the face with traces of cleavage planes plotted

Legend:

Fig. 1–6

Measurements of the elements of occurrence of the cleavage planes

Bedding	Bedding	Endocleavage	Endocleavage	Endocleavage	Endocleavage	Exocleavage	Exocleavage	Exocleavage	Exocleavage	Exocleavage	Exocleavage	Exocleavage	Exocleavage	Exocleavage	Exocleavage
\(h\)	\(L\)	Main	Main	End face	End face	I-a	I-a	I-b	I-b	II-a	II-a	II-b	II-b	III	III
\(h\)	\(L\)	\(h\)	\(L\)	\(h\)	\(L\)	\(h\)	\(L\)	\(h\)	\(L\)	\(h\)	\(L\)	\(h\)	\(L\)	\(h\)	\(L\)

Characteristics of the cleavage planes

Fig. 2

Fig. 3

Fig. 4

Fig. 5

Fig. 6

Composite stereogram
of the IV Internal seam, 4th wing—south,
I. V. Stalin Mine

Visible labels on the stereogram: main, cleavage, footwall, \(I_a\), \(I_{os}\), \(0\), \(90\), \(180\), \(270\).

Fig. 7

Composite stereogram
of the IV Internal seam, 4th wing—north,
I. V. Stalin Mine

Visible labels on the stereogram: main, cleavage, footwall, \(III_a\), \(I_a\), \(I_{os}\), \(0\), \(90\), \(180\), \(270\).

Fig. 8

Composite stereogram
of the IV Inner seam, No. 5 wing—south
I. V. Stalin Mine

Fig. 9

Visible labels in the diagram: “seam,” “principal,” “end”; angular markings: \(0^\circ\), \(90^\circ\), \(180^\circ\), \(270^\circ\).

Composite stereogram
of the IV Inner seam, No. 5 wing—north
I. V. Stalin Mine

Fig. 10

Visible labels in the diagram: “principal,” “end”; angular markings: \(0^\circ\), \(90^\circ\), \(180^\circ\), \(270^\circ\).

Composite stereogram
of seam IV of the Inner b syncline—rise side
Mine 3–3 bis

Labels visible in the diagram: seam; main; \(t_a\); \(t_b\); \(g\); \(0\), \(90\), \(180\), \(270\).

Fig. 12

Composite diagram
of the Gorely seam, western limb
of the b syncline

Labels visible in the diagram: main; seam; \(t_a\); \(t_b\); \(g\); \(0\), \(180\).

Fig. 11

Fig. 13

Legend:
Conventional symbols
— Principal cleavage
— Exocleavage I α
— Exocleavage II б
— [[unclear: exocleavage designation]]
— [[unclear: exocleavage designation]]

Inscription in the drawing:
Stalin Mine. Seam IV, Inner, no. 4, wing no. 2.

Fig. 14

a  b

Fig. 15

Inscription in the drawing:
spalling (?)

Fig. 16

Fig. 17

Fig. 18

Fig. 19

Fig. 20

Fig. 21

Fig. 23

Fig. 22

Visible labels in the figure: a, b; “Koksovaya”; [[unclear: seam or working name]]; “61 ok. k.”; [[unclear: central label, possibly “Ekzo 19”]].

Fig. 24

Visible labels in the figure: “120–105 m”; “1”; “2”; “e”; “n”; [[unclear: small numerical/letter markings]].

Fig. 26

Visible labels in the figure:

• VI layer
• intensive fracturing
• IV layer
• VI layer
• V layer
• III layer
• II layer

Fig. 25

Visible labels in the figure:

• [[unclear: small vertical label inside the right side of the figure]]
• [[unclear: small label near the lower left of the figure]]

Fig. 27

Fig. 28

Fig. 29

1. The zone system is also essentially a predatory system; however, the latter has its supporters, and therefore we shall have to dwell on it somewhat. ↩↩↩↩