The issue of determining the size of inter-chamber pillars is a very important issue, since it is closely related to issues of mineral loss. Factors such as the width of the chambers, the length of the chambers, the height of the pillar, the cross-sectional shape of the pillar, the physical and mechanical characteristics of the pillar rock should be reflected directly in the calculation formulas, and such factors as the nature of the complex of roof and soil rocks, the characteristics of the immediate roof and soil, the presence of aquifers, the shape and area of the excavation site - should be reflected in determining the magnitude of the load on the pillar and the nature of the pillar's work and, finally, the duration of the pillar's operation, work with or without backfilling of chambers, excavation of chambers with or without the use of blasting operations should be taken into account when choosing a safety factor.
The quantitative determination of the magnitude of deformations of rocks of various kinds in mine workings and the magnitude of rock pressure in the workings associated with these deformations raises the question of the fundamental possibility of applying to the solution of these problems the principles of the theory of elasticity and the theory of resistance of materials arising from the latter. It is very important to correctly solve the problem of rock pressure and rock deformation, since they essentially cover the entire complex of issues that is called rock pressure management (roof management) and which is the main and decisive factor in the correct conduct of mining operations. As a result of this circumstance, there is an urgent need to consider the possibility of applying the theory of elasticity to solving rock pressure control problems in more detail and to clarify the fundamental possibility (or impossibility) of such an application.
In the article “Determination of the sizes of interchamber pillars,” placed in the XVII-XVIII volume of “Notes of the Leningrad Order of Lenin Mining Institute,” an expression is given that determines the dimensions of the interchamber pillar through the adhesion force of a given rock C and its angle of internal friction. Determining the adhesion force through the tensile strength of the rock allows us to approach the issue of determining the sizes of inter-chamber pillars with great objectivity.
November 2, 1944 marked the 70th anniversary of the birth of one of the largest specialists in the field of mining mechanics, Academician Alexander Petrovich German.
The rate of advance of the faces, as is known, is of great importance not only from the point of view of the productivity of one or another section, but also from the point of view of work safety, facilitating the conditions for controlling rock pressure (roof control), as well as saving the consumption of fastening materials. The speed of advance is very important when developing adjacent layers.
In places of crossed or conjugate workings, the magnitude of vertical rock pressure, as is known, increases significantly. In this case, it is not possible to use the usual method of replacing the intersection of workings with a working of an equivalent span. Shape change theory is used to determine the magnitude of this rock pressure. Equations (8) and (10) represent the equations for changing the shape of the column in the case of straight or inclined intersections of shaft structures. The maximum change in the shape of the support angle is expressed by formulas (4) and (5). The equivalent width of the intersection of shafts is determined by formulas (9) and (15).
To correctly resolve the issue of the nature of the stressed state of the pillar and the deformations it experiences, it is necessary to have a correct understanding of the method of applying load to the pillar, since the latter determines the nature of the deformation - plastic or, conversely, elastic-brittle. In addition, it should be borne in mind that the very entry into operation of new cameras, which determines the increase in the load on the rear sight, does not occur immediately, but rather slowly and without jumps, but gradually. Having reached its maximum value—the full weight of the overlying rock strata—the load is not removed from the pillar, but continues to act for an indefinitely long time, which forces us to take into account the influence of time when considering the deformations of the pillar. Thus, it should be recognized that all conditions for loading interchamber pillars and the work of the load itself meet the conditions for the manifestation of plastic deformations.
