Conditions Determining or Necessitating the Need and Possibility of Mining Closely Spaced Steeply Dipping Seams in a Suite in Ascending Order

V. V. Proskurin

The study of the conditions determining the need and possibility of mining closely spaced steeply dipping seams in a suite in ascending order is a pressing problem both for the Kuznetsk Basin and for other basins of the USSR.

In investigations carried out by us [1], a number of cases were identified in which ascending mining of seams in suites was applied at mines of the trust “Kaganovichugol.” Subsequently, analyzing these cases, we came to the conclusion that, for production and for further scientific research, it is expedient to distinguish three groups of conditions:

1) conditions determining the need to mine closely spaced steeply dipping seams in a suite in ascending order;

2) conditions necessitating the raising of the question of applying an ascending order of seam mining;

3) conditions determining the possibility of raising the question of applying ascending seam mining in a suite.

On the basis of the investigations we carried out, the following list is given below of the conditions that determined the need and possibility of applying an ascending order of mining seams in suites at mines of the trust “Kaganovichugol” (Table).

Table

Taking into account the data given in the table and the results of investigations for other districts and basins [2–5], we consider that the conditions determining the necessity of mining closely spaced seams in ascending order are the following:

1) when the overlying seam in the suite is dangerous with respect to sudden outbursts of coal and gas, then mining the adjacent underlying seam first, as a protective seam, is absolutely necessary in order to ensure the safe conduct of underground mining operations;

2) when the overlying seam in the suite is watered, then, in order to drain it, it is necessary to apply ascending mining of the upper pair of seams;

3) when the uppermost seam in the suite has a higher gas content than the adjacent underlying seam, then, for the purpose of degassing the upper seam, it is necessary to apply ascending mining of the upper pair of seams.

Among the conditions necessitating the raising of the question of applying mining of closely spaced steeply dipping seams in ascending order, we include:

1) when the opening of a suite of closely spaced steeply dipping seams is carried out from the side of the footwall; then, in order to shorten the time required for the mine to attain its designed production capacity, it becomes necessary first to mine the underlying seam;

2) when a group haulage roadway, for reasons of technical expediency and economic advantage, is driven not along the lowest seam in the suite but higher, then there arises the necessity, in order to increase the active line of stoping faces, to ensure the planned output of the mine, and to mine the opened reserves more rapidly, to conduct stoping operations in advance on the lower seams;

3) when, other conditions being equal and technically permissible for the use of either ascending or descending mining of the seams in a suite, the useful thickness of the underlying seam is considerably greater than the useful thickness of the overlying seam, then there arises the necessity, in order to increase the productive capacity of the mine, first to mine the underlying, more thick seam;

4) when the underlying seam is represented by coals of higher quality, and the overlying seam by low-grade coals, or when it becomes necessary first of all to mine the lower seams with coking coals;

5) if the coals of the seam along which the group roadway has been driven are prone to spontaneous combustion, and this seam is not the lowest in the suite, then, when mining the panel from the shaft toward the boundaries of the mine field, the reserves of this seam, for reasons of fire-prevention safety, must be preserved until the time when stoping operations on the other overlying seams of the suite reach the boundaries of the mine field; then there arises the necessity of putting the lower seams into operation;

6) if the overlying seam has medium thickness and is represented by very strong coals, then, in order to reduce the strength of the coal, it becomes necessary to apply ascending mining of the pair of seams; expediency will be achieved only if this order of mining ensures an increase in labor productivity and a higher economy of extraction as a whole for the pair of seams.

Among the conditions determining the possibility of raising the question of applying mining of closely spaced steeply dipping seams in ascending order, it is necessary to include:

1) roof control with complete, dense, and promptly erected stowing of the worked-out space;

2) the presence at the mine or ore mine as a whole of a well-developed centralized, mechanized stowing system;

3) the use of a shield mining system, which is characterized by: a high rate of advance of the working face along the dip of the seam and dense filling of the worked-out space with caved rocks of the overburden deposits, displaced following the movement of the shield;

4) the presence of thick, sufficiently loose, readily caving overburden deposits, ensuring more complete filling of the worked-out space;

5) the presence of an interseam rock thickness whose thickness exceeds the height of the caving zone;

6) high mechanical strength of the interseam rock thickness and the presence of rock partings composing the interseam, prone to plastic bending;

7) the absence, in the interseam rock thickness, of discontinuity disturbances and especially of open cracks parallel to the line of the working face;

8) a small floor height, which, other conditions being equal, ensures a small height of the caving zone at the upper boundary of the extraction field.

The criterion of necessity for applying ascending extraction of seams in a suite should be a technical analysis.

The criterion of possibility for applying ascending extraction of seams in a suite may be technical and economic expediency, achieved by safer working conditions, higher labor productivity in coal breaking, more rapid preparation and commissioning of new extraction fields and with more productive seams, more rapid commissioning of seams with high-quality coals, use of the maximum possible length of the active longwall front, and the smallest losses of coal in the subsurface.

REFERENCES

1. Proskurin V. V. Investigation of the order and methods of mining closely spaced steeply dipping seams of the Kiselevsk deposit of Kuzbass. In: Questions of Mining Thick Seams of Kuzbass. Ugletekhizdat, 1953.

2. Nekrasovskii Ya. E. Mining of steeply dipping seams with sudden outbursts of coal and gas. Ugletekhizdat, 1948.

3. Proskurin V. V. The Prokopyevsk Mine of Kuzbass. Tomsk, Poligrafizdat, 1951.

4. Strelnikov D. A. Mining of closely spaced seams of medium thickness by a long-pillar system. Vestnik Sibirskikh inzhenerov, No. 5, 1925.

5. Yarovoi I. M. Manual for the mining of seams hazardous with respect to outbursts of coal and gas. Ugletekhizdat, 1949.