Calculating the stresses in solid rock from measurements of roof movement in a coal seam

Abstract

Complete information on the mechanical state of solid rock is given by a knowledge of its stress-strain state. However, experimental methods of measuring the stresses in solid rock are still in the development stage. Analyrical methods of attacking the problems of stress redistribution in rock due to mining operations can be solved in the general form, but as a rule it is impossible to use these methods at present to solve practical problems in particular geological and mining conditions. The stress pattern in the rock can be found by a method which combines the possibility of analytical solutions with the use of data on rock pressure phenomena.In mine observations the most widely used method of investigation is observation of movements of the side rocks due to mining operations. The experimental-analytical method of determining the stress pattern, developed in the Laboratory of Mining of the Institute of Mining of the Siberian Branch of the Academy of Sciences of the USSR, permits us to determine the changes of stress around mine workings from measurements of the movements of the roof while a coal seam is being worked.As a result of mining operations, there is a spatial redistribution of the stress-stain pattern in me rocks. We will consider this spatial pattern in cross sections, assuming that each such cross section obeys the conditions for a plane problem. In this case, the caiculated stress-strain pattern of the rock will usually be greater than the actual spatial redistribution of stresses.The redistribution of the stress-strain pattern due to mining operations will also vary with time (as well as space), owing to the gradual advance of the face and to the theological properties of the rock mass [l].