Toward the Development of a Methodology for Forecasting the Disturbance of Mine Fields in Kuzbass

A. A. Belitsky

Usually, exploration of coal deposits from the surface, even with a dense network of exploratory workings, makes it possible to determine only the principal structural features—folds of considerable size and relatively large tectonic faults. Meanwhile, the development of underground mine workings is strongly influenced by so-called small structural forms—minor folds and faults, pinches and swellings of seams, and fracturing. In many deposits of Kuzbass—in the Osinovskoye, Prokopyevsk-Kiselevsk, Bachat, Anzhero-Sudzhensk, and others—the broad and varied occurrence of these small structural forms is one of the main difficulties that must be overcome in developing coal seams. It is generally known that the tectonic disturbance of these deposits affects the choice of mining system, the mechanization of operations, the increase in coal losses, the stability of mine workings, and, ultimately, labor productivity and the cost of the extracted mineral.

By the present time, extensive material on mine tectonics has accumulated at the mines of Kuzbass. Although all this material has not yet been sufficiently studied and generalized, it is nevertheless already possible to attempt, as a first approximation, to outline the general regularities of the mine tectonics of Kuzbass. It seems to us that some of these regularities may make it possible to outline ways of forecasting the tectonic structure of areas not yet exposed by preparatory and extraction workings. The enormous importance of such forecasting is self-evident.

In tectonic terms, the greatest interest in the Kuznetsk Basin is presented by the well-studied coal-bearing deposits of the southwestern near-Salair part of the basin—the Prokopyevsk-Kiselevsk, Bachat, Belovo, and Leninsk-Kuznetsk districts—and by the coal-bearing deposits of the northern part of the basin—the Anzhero-Sudzhensk district. Despite the fact that these parts of the basin are located at opposite ends and in different tectonic blocks, their tectonic structure is characterized by many common regularities.

The tectonics of the coal-bearing deposits of the southwestern near-Salair part of the basin is associated with the overthrusting of the Salair Ridge onto Kuzbass. In this connection, in the near-Salair belt of the basin there formed a distinctive tectonic zone, approximately 50–60 km wide (Fig. 1). The coal-bearing deposits of this zone are cut by large longitudinal faults into

a series of scales, among which, counting from the boundary into the interior of the basin, one may distinguish the Prityrgan, Chertin, Belovo, and Leninsk-Kuznetsk

Fig. 1. Geological map of the Kuznetsk coal basin, compiled by the Kuzbassuglegeologiya Trust under the editorship of I. I. Molchanov, E. M. Senderzon, and N. M. Belyanin, using the geological map of V. I. Yavorsky.

scales. These large faults are traced for tens and hundreds of kilometers along the strike. All of them belong to the thrust-fault type, dipping to

southwest toward the Salair Ridge at an angle of 60–80° and have a considerable vertical displacement amplitude (up to 1000 m and more).

The rocks within each slice are gathered into folds, which are likewise linearly elongated in a northwestern direction, parallel to the front of the Salair thrust. Among these folds one can distinguish a number of more or less complex brachyfolds, which in turn are cut by longitudinal faults of smaller scale, also dipping toward the Salair thrust at an angle of 60–80°. Thus, for example, within the coal-bearing deposits of the Prityrgan slice in the Prokopyevsk district there are ten such faults, which, together with the numerous folds of this district, create a rather complex tectonic structure (Fig. 2).

Fig. 2. Transverse-vertical section of the Prokopyevsk district of Kuzbass.
1 — Kuznetsk suite; 2, 3, 4 — Upper, Middle, and Lower strata of the Balakhonka series;
5 — Ostrog suite; 6 — Lower Carboniferous deposits; 7 — Middle Devonian deposits;
8 — tectonic faults.

The intensity of the basin tectonics weakens from the western boundary toward its center.

The tectonics of the Anzhero-Sudzhensk district is associated with the overthrusting of mountain masses of the Kolyvan-Tomsk folded region onto the coal-bearing deposits of the basin. Here, too, more or less complex brachyfolds are cut by longitudinal tectonic faults of the reverse-fault type, whose scale, however, is smaller than in the near-Salair belt. According to R. G. Kolomin, the fault planes of these faults also dip westward at an angle of 40–70° (see Figs. 4 and 5 in the article by R. G. Kolomin in the present collection).

Thus, on the whole, the fault structure of the described coal-bearing deposits of Kuzbass is characterized by a slice-like structure with successive overthrusting of the western slices onto the eastern ones along relatively large longitudinal faults (Figs. 1 and 2). It should be noted, however, that these faults do not exert a substantial influence on...

mining operations. The largest of these are natural boundaries of industrial districts. Others, however, are boundaries of mine fields or of operating sections.

The greatest influence on the conduct of development and extraction work is exerted by minor faults, whose dense network in places creates exceptionally difficult conditions for the mining of coal seams. Therefore, it is of enormous practical interest to identify the regularities in the manifestation of minor faults in order to determine the possibility of forecasting them in areas not yet opened up by development and extraction workings.

Studying the manifestation of minor faults in the mines of Kuzbass, especially in the Prokopievsk-Kiselevsk, Anzhero-Sudzhensk, Leninsk, and Belovo districts, it is easy to note that minor faults are spatially always associated with major longitudinal faults. On the other hand, a connection is established between minor faults and the jointing¹ of coal and of the enclosing rocks, which is clearly visible directly in underground mine workings, and also when compiling circular diagrams of minor faults and jointing, for example in the Anzhero-Sudzhensk district (Figs. 4, 5 in the article by R. G. Kolomin in the present collection). This connection becomes comprehensible if one imagines the history of the formation and development of the tectonic structure. At first, plastic deformation predominated, in the course of which the coal-bearing deposits were gathered into folds; in addition, a large number of slip planes arose in the rocks; the latter gradually developed into jointing². Then, when the possibilities for plastic deformation began to be exhausted and, in connection with this, the rocks began to fail, there arose first of all longitudinal faults, which, in places of the greatest concentration of stresses, gradually merging and growing along the strike and dip, formed major longitudinal faults, well studied in the Salair-adjacent belt of Kuzbass. Simultaneously, in the course of the development of these faults, a dense network of minor faults formed along their flanks; these arose along the jointing, as along the directions of least resistance. It is therefore quite understandable that, near major longitudinal faults, distinctive zones of destroyed rocks formed. Since in the districts of Kuzbass a complex network of jointing is usually observed, the minor faults correspondingly have the most varied orientations. Under these conditions, a typical block structure arose within the indicated zones.

It is understandable that, in this case, minor faults must also be distinguished by great variety in form. Among them are found conformable and nonconformable reverse faults, thrusts, normal faults, and upthrow faults³.

We may accept the spatial connection of minor faults with major ones as an important regularity for developing a methodology for forecasting the disturbance of mine fields. Indeed, we observe everywhere that where major faults are absent, minor faults are also absent or occur comparatively rarely. This is not difficult to verify if one examines maps of seam outcrops beneath the overburden and especially seam maps for individual mine fields, as well as cross-vertical—

Scale 1:10000

100 0 100 200 300 400

SW

NE

Southwest

Serafimovich seams

Abinsk anticline

Golubevka anticline

Malaya anticline

Fig. 3. Transverse-vertical section of the left-bank part of the Prokopyevsk district of Kuzbass.

80 0 80 160 240 320 m

Internal IV

Internal III

Internal II

Abramov seam

Break

Section along I--I

265 m

215 m

165 m

65 m

Fig. 4. Seam map of the 220 m horizon of the Golubevka anticline of the Stalin Mine, Prokopyevsk district of Kuzbass. Thick solid lines indicate coal seams; dash-dot lines indicate tectonic faults.

tical sections, especially in the Prokopyevsk-Kiselevsk, Anzhero-Sudzhensk, Leninsk, and Belovo districts of Kuzbass. This regularity is most clearly expressed in the left-bank part of the Prokopyevsk-Kiselevsk district, within the Abinskaya, Golubyevskaya, Malaya anticlines and the “Muraveinik” anticline (Figs. 3 and 4). Here the northeastern limbs of the last three folds are intersected by large longitudinal faults of the overthrust type—GG, JJ, J′J′—with which the formation of a dense network of small faults is associated. In individual areas the degree of disturbance of the seams by these faults reaches such proportions that considerable coal reserves have to be written off as losses because it is impossible to work them. A different picture is observed on the southwestern limbs of the indicated folds. Here there are no large longitudinal faults, and therefore small faults are encountered comparatively rarely. The coal seams on these limbs are excellently persistent over a long distance both along strike and down dip, and therefore their development here does not encounter substantial difficulties.

In the right-bank part of the district this regularity is also clearly revealed. For example, in the field of the Kalinin Mine, on the flanks of large faults, and also in the hanging wall of the large fault of the Voroshilov Mine (Fig. 5), there is a large number of small faults. In such areas as the first syncline in the northwestern part of the Prokopyevsk district and the second Tyrgan anticline in the Kiselevsk district (the Abinsk areas), one may observe a simple structure unusual for this district, due to the fact that the coal-bearing deposits of these folds are not disturbed by major tectonic faults.

This regularity is expressed even better in the Anzhero-Sudzhensk district. Considering from this point of view the structural maps for all seams worked in this district, one may note that small faults are widely developed mainly on the flanks of relatively large longitudinal faults. With the disappearance of the latter, the small faults also almost completely disappear. Thus, at Mine 5/7, in the upper package of seams of the Central Suite—the Desyaty and Andreyevsky seams (Fig. 4 in the article by R. G. Kolomin)—small faults within the worked-out part of the mine field were encountered mainly in the northern part of the mine field, while in the lower package of seams—the Dvoinoy, Tonky, Petrovsky, and Koksovy seams—they were encountered in the southern part of the mine field (Fig. 5 in the article by R. G. Kolomin). Looking closely at the structural maps of these seams and the transverse vertical sections, one can easily explain this distribution of small faults. The upper package of seams is strongly broken by longitudinal faults in the north of the mine field; in the middle part of the field the fault structure of these seams becomes simpler, while in the south the indicated seams are not intersected at all by longitudinal faults. Conversely, the lower package of seams proved to be strongly broken by longitudinal faults in the south of the mine field, whereas to the north they retreat eastward; therefore, within the worked-out part of the field this package of seams proved not to be affected by longitudinal faults.

In connection with the question under consideration, it is appropriate to note that in the Anzhero-Sudzhensk district, against the background of a complex tectonic structure, there are large fields with a very simple structure. Thus, for example, at Mine 5/7, in the Desyaty and Andreyevsky seams, from the main crosscut to the southern boundary (more than three kilometers along strike), with the exception of several small faults, mine workings recorded a simple structure without faults or additional folds. Here the angle of dip is well maintained—from 20° to 35°—and significant deviations from the average seam thickness are rarely encountered.

Scale: 80 0 80 160 240 320 m

VI Internal

Typical

II Internal

IV Internal

VI Internal

Gorely

Molodoy

Section along I–I

W — E

IV Internal

II Internal

II Internal and Internal

Characteristic

Gorely

IV Internal

Fig. 5. Seam map of the hanging wall of the concordant upthrow EE of the 220 m level of the Voroshilov Mine, Prokopyevsk district of Kuzbass. The symbols are the same as in Fig. 4.

We observe a spatial connection between small and large faults also in the Leninsk district. The tectonic structure of this district is characterized by gentle and relatively simple brachysynclinal folds, elongated along the near-Salair belt. However, some operating mines, especially the Yaroslavsky mine, as well as the northern part of the field of the Zhurinka 3 mine, situated along a major longitudinal fault—the Zhurinka reverse fault—have recorded a large number of small faults. Their number decreases sharply with distance from the Zhurinka reverse fault and almost completely disappears 100–150 m from it.

It should be noted that the connection of small faults with major tectonic faults is a general regularity in structural geology. We also observed this connection when studying the tectonics of the mine fields of the Saransk and Promyshlenny areas of the Karaganda basin, and also when examining materials characterizing the structures of ore fields at a number of Siberian mineral deposits. This connection was established and described long ago for various mineral deposits [2, 3, 4]. However, many assume that small faults arise and develop on the flanks of large faults as shear and detachment planes in the process of displacement of the sides of the fault relative to one another (feathering fractures). Our studies have shown that small faults on the flanks of a large fault, as a rule, are not newly formed, but develop along fracturing that was mainly laid down in the form of slip planes already at the stage of plastic deformation of the coal-bearing deposits before the formation of the large fault.

The factual material studied on the mine tectonics of Kuzbass makes it possible to establish not only the spatial connection of small and large faults, but also to outline a regular connection between the intensity of disturbance of coal seams by small faults and the form of their manifestation with the structural features of the deposits. In this connection, attention should be paid to the structural asymmetry of folds in the Kuznetsk basin. It turns out that the limbs of folds dipping to the southwest and northeast are very often deformed quite differently. The limbs of folds dipping to the southwest in the near-Salair belt face toward the Salair Ridge, from which, as is known, an active force flow acted. The tangential component AB (Fig. 6) is directed upward

Fig. 6. Orientation of the tangential component AB of the force flow OB on the limb of a fold dipping to the southwest and northeast.

along the bedding in the direction of least resistance (the ground surface). As a result, intensive bedding-plane movements occurred on the indicated limbs, which led to the formation of pinches

and swellings of beds, additional folds, and also tectonic ruptures of the type of conformable thrust faults.

Especially clear examples of such a structure are the northeastern limbs of the II and III synclines, as well as the southwestern limb of the Maganak anticline of the Prokopyevsk–Kiselevsk district and the eastern limb of the Anzher syncline. Here additional folds, pinches and swellings of beds are widely developed, causing considerable fluctuations in the thickness of coal seams. In the flanks of large longitudinal ruptures of the type of conformable thrust faults on limbs dipping to the southwest, small ruptures arose, predominantly also conformable thrust faults and, more rarely, normal faults. It should be noted, however, that, often adapting themselves to bedding as the direction of least resistance, conformable thrust faults cut through the beds relatively easily and therefore deformed the rocks adjacent to the rupture comparatively weakly. On the whole, the zone of destroyed rocks in the flanks of large longitudinal ruptures of the conformable-thrust type is characterized by relative simplicity (Fig. 5).

In a different setting, coal seams were deformed on limbs dipping to the northeast. If on limbs dipping to the southwest, from the very first moment of fold formation, favorable conditions were created for bedding-plane movements, and therefore in individual cases tectonic ruptures of the conformable-thrust type were initiated even at early stages of folding, then on limbs dipping to the northeast, owing to the fact that the tangential component is directed downward, toward the side of greatest resistance, such a release of stresses was impeded. Bedding-plane movements on these limbs proved possible only at the expense of support; but, not being the active force of the latter, it played a much smaller role in this process. Therefore, on limbs dipping to the northeast, ruptures of the conformable-thrust type, as a rule, did not arise, and additional folds were formed comparatively rarely. On these limbs, large longitudinal ruptures of the nonconformable-thrust type were initiated. In contrast to ruptures of the conformable-thrust type, a denser network of small ruptures usually arose in the flanks of nonconformable thrust faults. This is explained by the fact that the angle between the bedding and the rupture surface increased considerably, which led to an increase in friction and, consequently, to greater deformation of the rocks in the flanks of the rupture. Under these conditions, in the flanks of large ruptures of the nonconformable-thrust type there arose a more extensive zone of destroyed rocks; at the same time, normal faults and nonconformable thrust faults had predominant development here, while conformable thrust faults and reverse faults are encountered rarely. In general, the zone of destroyed rocks in the flanks of large longitudinal ruptures of the nonconformable-thrust type is characterized by comparatively greater width and complexity, as a result of which the mining of coal seams in such zones often encounters very great difficulties and in many cases may prove economically inexpedient. A good example of the structure described is the hanging wall of rupture GG at the Stalin Mine (Fig. 4¹).

It is necessary to note that small ruptures of the normal-fault type are widespread in deposits with steep dips of the beds (Prokopyevsk–Kiselevsk). In deposits with gentle dips of the beds (Anzhero-Sudzhensk, Belovo, Leninsk), instead of ruptures of the normal-fault type, upthrusts are encountered. This is explained by the different geometrical relationships of the rupture cracks and the bedding—

... and, in connection with this, by the different conditions of movement of individual blocks of rock on the flanks of major tectonic fractures.

Thus, on the opposite limbs of folds on the flanks of major longitudinal fractures of the type of conformable and nonconformable thrust faults, zones of destroyed rocks arose that differed in width, in the intensity of their manifestation, and in complexity. However, it is necessary to trace how the intensity of manifestation of small fractures changes along a major tectonic fracture within one limb of a fold. The greatest disturbance of the seams is usually observed directly at their truncations by major tectonic fractures. The zone of influence of these fractures across the strike and along the dip of the seams, as we have already noted, is different and reaches 200–300 m for conformable-dip fractures, and 300–400 m for nonconformable-dip fractures (Figs. 4 and 5). By tracing this zone along the strike and along the dip, one may become convinced that in most cases it gradually dies out with increasing distance from the truncation of the seams by a major tectonic fracture. Thus, studying the deformation of rocks on the hanging wall of the nonconformable thrust fault GG (Fig. 4), one can see that the greatest number of small fractures occurs in the sector where the seams are truncated. As the distance from the truncation of the seam VI Vnutrennii increases, the number of small fractures becomes smaller, and toward the closure of the fold they almost disappear. To the south, after the truncation of the Moshchnyi seam, the fracture approaches the fold axis and farther along its entire extent lies alongside the Bezymyannyi and Moshchnyi seams; nevertheless, the latter are nowhere intersected by small fractures.

The same can be observed in the hanging limb of the conformable thrust fault EE (Fig. 5). In the north, within the sector where the seams are truncated by the thrust fault EE, the number of small fractures is greater, but toward the south, almost to the closure of the synclinal fold, they gradually disappear, although throughout this entire extent the indicated thrust fault lies alongside the Gorelyi seam but does not cut it directly. In the south the thrust fault EE was intersected by crosscut No. 8 of the Kaganovich Mine. It is curious to note that the rocks on the flanks of this largest fracture have completely calm bedding (Fig. 7), and the fissure itself, having adapted here to the bedding, was so weakly expressed that during the driving of the crosscut it was not noticed at first. They began to search for the fissure only after seam III Vnutrennii had been cut, following the Podspornyi seam, which indicates a stratigraphic displacement equal to almost two thicknesses of the Balakhon series.

Fig. 7. Geological section in the plane of crosscut No. 8 of the Kaganovich Mine, Prokopyevsk district of Kuzbass.

Studying the intensity of manifestation of small fractures on the flanks of major fractures, especially on the flanks of major conformable thrust faults, one can often observe over a great extent an absence of small fractures, even in cases where the seam is situated alongside a major fracture but is not directly truncated by it at the given horizon. However, it is not uncommon for sectors where small fractures are absent to alternate with sectors where they occur in large numbers. Such a sector is, for example, the field of the Yaroslavsky Mine of the Leninsky district, which...

is located on the hanging wall of the Zhurinka thrust fault. The neighboring mine fields—Zainskoye 1–2 to the northwest and Komsomolskoye to the southeast—have almost no minor faults, whereas many were encountered in the field of the Yaroslavsky mine. Considering the structure of these three mines, it is easy to see the reason for this phenomenon (Fig. 8). The fact is that within the Yaroslavsky mine the seams dip very gently—5–8°, whereas in the Zainskoye 1–2 mine field they dip at 15–20°, and in the Komsomolskoye field at 20–45°. Consequently, transverse bends of the seams are rather clearly outlined approximately along the boundaries of the Yaroslavsky mine field. These bends, as the most weakened places, are associated with transverse faults—the Western and Eastern Kamyshanka thrust faults, which are apophyses of the Zhurinka thrust fault. It is clear that the Yaroslavsky mine field underwent complex deformation, which led to the formation of a large number of minor faults. Since this wing dips concordantly with the dip of the Zhurinka thrust fault to the southwest, the dominant form of minor faults here is concordant thrust faults.

Fig. 8. Copy from a map of seam outcrops beneath drift deposits. Leninsk district of Kuzbass.

We observed an analogous case at the Babanakovskaya mine of the Belovo district. This mine works the southwestern wing of the Belovo syncline, which is distinguished by a fairly simple tectonic structure. However, in the south of the mine field there is also a transverse bend of the seams. The formation of a transverse fault—an apophysis of the Kutanovka thrust fault—is associated with this bend. In the hanging wall of this fault a thick zone of minor faults formed, which has been traced by mine workings along the strike for about 500 m. Here the wing of the fold dips discordantly with the Kutanovka thrust fault to the northeast; therefore the dominant form of minor faults is discordant thrust faults and reverse faults.

Thus, a definite connection is emerging between the manifestations

Fig. 9. Seam map of the 245 m level of the field of the “Tom-Usinskaya I” mine and a transverse-vertical section in the plane of exploration line 11—11.

by small faults and various kinds of bending of the strata in the flanks of large faults—by additional folds, drag folds, especially transverse bends of the strata, etc. This relationship can be observed in all districts of Kuzbass. In particular, it has been noted, especially in deposits with steep dip angles of the strata of the Balakhon series, that in the closures of synclinal folds small faults in the flanks of large faults develop more intensively than in the closures of anticlinal folds, which, however, is understandable, since the latter are usually deformed under simpler conditions.

A regular connection has also been noted between the formation of a complex fault structure and additional folds and bends of the axes of folds. For example, in the Prokopyevsk–Kiselevsk district, the complex tectonic structure in the north near Novosergeevo, Afonino, and Kiselevka, and also in the south at Zenkovo and Spitsino, is connected with bends in these sectors of the principal synclinal folds of the district. It is characteristic that the largest longitudinal tectonic faults, having their maximum development in the sectors of the indicated bends of the fold axes, almost completely die out between Prokopyevsk and Kiselevka. Probably the complex mechanism of bending of fold axes is accompanied by the formation of faults and additional folds.

Finally, it should be noted that the intensity of manifestation of small faults will depend on the number of large faults on the limb of the fold and on the distance between them. Thus, for example, the very complex fault structure of the Kalinin mine in the Prokopyevsk district is due to the fact that a narrow belt of coal-bearing deposits of this mine field (about 1 km) proved to be disturbed by four large longitudinal faults AA, DD, MM, and SS. The dense network of small faults in individual sectors of the Anzhero-Sudzhensk district is likewise explained by the concentration of longitudinal faults within a comparatively narrow area. For example, in the northern part of mine 5/7 the Desyaty and Andreyevsky seams, within a narrow belt of about 500 m, are cut by seven longitudinal faults. Although these faults, in scale, are considerably smaller than analogous faults of the Prisalaire belt of Kuzbass and, moreover, all belong to the type of conformable thrust faults, nevertheless, being closely spaced, they together create a dense and complex network of small faults.

It has also been observed that in some cases small faults arise in the closures of the principal synclinal and additional folds without connection with large tectonic faults, especially when the axes of the additional folds form a more or less significant angle with the dominant strike of the coal-bearing sequence of the given district. In this case such folds undergo complex deformation and, as a result, are broken by numerous tectonic faults, whose orientation may also be varied. Such is the origin of the small faults in the southern part of the eastern limb of the Abinsk anticline of the Stalin mine, within the limits of a flexure-like bending of the strata of the upper sequence. In this way there arose numerous faults in the seams opened by the “Tom-Usinskaya 1–2” mine (Fig. 9).

Thus, by studying the structural features of coal seams along large tectonic faults and the relationship of coal seams to the fault itself, as well as the character of the principal and additional folds, it is possible in advance to outline sectors where small faults will practically not be encountered and where they may occur in large numbers. The basis for such a forecast, of course, will be the materials of preliminary exploration of the mine field, in the course of which [[unclear: sentence continues on next page]]

are all the largest structural elements of mine fields. Analyzing seam maps and geological sections compiled along exploration lines, we shall, in each specific case, using the regularities set forth above, mark out areas of differing degrees of disturbance.

Considering from this point of view, for example, the geological map of the Leninsk and Belovo districts, it may be said that the Leninsk and Chertinsk brachysynclines are in the most favorable position. In both cases the seams are, for the most part, not cut by large faults; on the limbs of these folds, bends of the seams are encountered rarely. The least favorable conditions for mining may be expected within the Egozovo-Krasnoyarsk brachysyncline, especially on its southwestern limb adjoining the Zhurin thrust. Here the seams are often cut by this thrust and form a number of complex additional folds. In addition, this limb dips to the northeast and, consequently, faults of the discordant upthrust and overthrust type may be expected here. The southwestern limb of the Belovo brachysyncline is also in a less favorable position, since the seams here are cut by the Kutanov thrust and have additional folds. It should also be taken into account that this limb dips to the northeast.

In mine fields well studied by exploration and mining operations, it is possible to give a more substantiated and accurate forecast, which, in particular, is presented by R. G. Kolomin for mine 5/7 of the Anzhero-Sudzhensk district in the present collection.

Undoubtedly, all these regularities can be used for a more rational direction of development workings and operational exploration. However, they may also be duly taken into account in the process of preliminary and detailed exploration, especially in determining the density of the exploration grid and the spatial arrangement of exploration workings on different limbs of folds in the walls of large concordant and discordant thrusts. Taking these regularities into account is also of great importance for increasing the reliability of the calculated reserves of industrial categories \((A_2 + B)\). Thus, at present it has been established that in many mine fields of Kuzbass, owing to complex tectonics, the reliability of calculated reserves of industrial categories is very low. A number of examples may be cited (the Kalinin mine, the “Ziminka 3—4” mine, the “Krasnogorskaya” mine, the Vakhrushev mine, and others in the Prokopyevsk-Kiselevsk district; mine 9—15 of the Anzhero-Sudzhensk district), when recalculation of reserves, after additional operational exploration with extensive use of underground mine workings, led to a reduction in reserves of industrial categories as compared with detailed exploration, although the density of the exploration grid in some cases increased considerably.

The reason for the low reliability of the calculated reserves of industrial categories may be shown by the example of calculating reserves for seam II Internal of the eastern limb of the Golubev anticline in the hanging wall of the large discordant thrust GG (Fig. 10). As we have already noted, in the hanging wall of this fault a dense network of small faults is recorded in all seams—the figure shows only the largest of them. It is no accident that this seam, opened by underground mine workings on four working horizons, has still scarcely been mined. Such severe disturbance of this seam, despite its detailed exploration by underground mine workings and by a large number of boreholes, compelled a considerable part of the reserves to be assigned to category \(C_1\).

It would seem that, in calculating coal reserves for this seam for the pre-

Fig. 10. Calculation of reserves on the vertical projection of seam II Inner on the hanging wall of the major fault GG. The number or letter in a circle denotes the number of the calculation block; the letter to the left of the circle denotes the reserve category; the number to the right of the circle denotes the dip angle of the seam; the small black circles denote points where the seam was undercut by boreholes.

by workings in a well-explored area, on the basis of data from a comparatively sparse network of boreholes, it would have been necessary to take the revealed regularity into account and properly assess the reliability of the reserves. This, however, was not done. It is clear from the figure that the authors of the reserve calculation completely ignore this regularity and calculate reserves near the margin of the large fault GG, on the basis of only a single point of intersection by a borehole situated 500–600 m from the well-studied area, in the highest categories, A₂ and B. There is no doubt that when this area is opened up by mine workings, a dense network of minor faults will be encountered there, as a result of which the indicated reserve categories will likewise be reduced to C₁.

The example considered is not an isolated case. Many such examples can be cited for Kuzbass. Analysis of the factual material shows that such an approach to assessing reserve categories is, apparently, the prevailing one. Therefore, the need has become urgent to reconsider many questions of exploration methodology in highly disturbed coal deposits, making use of the regularities of mine tectonics.

Thus, at the present time there are sufficient possibilities for developing a methodology for forecasting the disturbance of mine fields in Kuzbass. The task is, by studying and generalizing the accumulated material on the tectonics of mine fields in operating mines and in geological exploration parties, to establish the regular connection of various structural elements and the manifestation of these connections under specific geological conditions.

There is no doubt that, along with the general regularities of deformation of coal-bearing deposits, in each coalfield it is necessary to study the specific features that may obscure the general regularities or create distinctive structural elements in individual areas. For example, the manifestation of minor faults unrelated to large faults should be studied in detail, something that can be observed in places in the coalfields of Kuzbass. In these cases, the formation of minor faults will probably be connected with the peculiarities of the development of individual folds, as was already noted above.

The significance of specific deformation conditions can be shown by comparing coalfields in which coal-bearing deposits of the Balakhonka and Kolchugino series are developed. The rocks of the Balakhonka series, being older deposits, at the final stage of folding proved to be sufficiently brittle; as a result, they were easily destroyed with the formation of a dense network of tectonic faults. The rocks of the Kolchugino series by that time were less brittle and, consequently, had not yet lost the capacity for plastic deformation. Important evidence of this is the weaker manifestation of fracturing in the rocks of the Kolchugino series (slip planes had not yet had time to be properly transformed into fracturing), whereas in the rocks of the Balakhonka series it is expressed quite clearly. In addition, the rocks of the Balakhonka series, being located directly at the source of pressure, proved to be more strongly deformed than the rocks of the Kolchugino series. Therefore, in the rocks of the Kolchugino series, even at seam margins bounded by large tectonic faults, minor faults are often absent if there are no corresponding bends of the seams near the large fault. Such a situation can be observed in the field of the Zhurinka 3 mine of the Leninsky district, where the Podzhurinsky seams have been worked up to the margin bounded by the Zhurinsky thrust fault, yet minor faults were not encountered here.

It appears to us that, in the future, on the basis of these studies it will be necessary to change the procedure for preparing graphic material and the content of the corresponding sections of reports, usually compiled as a result of exploration of mine fields. The chapter of the report on the tectonics of the mine field should contain, in addition to a formal description of the recorded structural elements, also a detailed analysis of the tectonic structure and a forecast of the disturbance of the mine field by small structural forms. On the graphic materials—seam maps and sections—it is necessary to show zones where a large number of small faults, intensive manifestation of fracturing, etc., are expected to be encountered. Undoubtedly, such material will make it possible to design subsequent stages of exploration more rationally and to select the appropriate density of the exploration grid. Moreover, the exploration grid most often cannot be the same within a single mine field. Thus, on the flanks of large longitudinal faults of the type of oblique reverse faults, the exploration grid should be denser than on the flanks of a large longitudinal fault of the type of a conformable reverse fault.

The regularities noted in the present work and the recommended method of preparing graphic materials will also be of great importance for mine construction and for the development of preparatory and extraction workings. In particular, it will be possible not only to establish zones of development of small faults, but also to predetermine in advance their prevailing form, which is of great importance for searching for the displaced wings of disrupted seams.

The development of a methodology for forecasting the disturbance of mine fields urgently requires a fundamental improvement in the geological servicing of coal mines, especially the geological documentation of underground mine workings, since a forecasting methodology can be developed essentially on the basis of analysis and generalization of geological observations in underground mine workings.

CITED LITERATURE

1. Belitsky A. A. Classification of tectonic faults and geometric methods for studying them. Gosgeolizdat. 1953.

2. Volfson F. I. Structures of endogenous ore deposits. Fundamental problems in the study of magmatogenic ore deposits. Publishing House of the Academy of Sciences of the USSR. 1953.

3. Kreiter V. M. Structures of ore fields and deposits. Gosgeoltekhizdat. 1956.

4. Peck A. V. Fracture tectonics and structural analysis. Publishing House of the Academy of Sciences of the USSR. 1939.

1. It cannot but be noted that the regularities described and, in particular, the structural asymmetry of folds are important evidence of the tangential origin of the Kuzbass folds. ↩↩

2. During this period, longitudinal tectonic faults may arise on the limbs of folds facing toward the active force flow; later, together with the twisting of the limbs of the folds, these faults are also twisted or even gathered into folds. Such faults are known in Kuzbass; however, they occur comparatively rarely. ↩

3. These forms are described in detail in the work of A. A. Beltitskii [1]. ↩