Use of photoelastic analysis of models to estimate the fracture of the rock near an underground working

Abstract

We propose a new approach to the estimation of fracture of rocks near underground workings on the basis of a photoelastic analysis of models. We verify our views and concepts with several series of experiments which show that our proposals have promise. In order to carry out our recommendations, it is necessary to know the diagrams of mechanical state of the prototype and model materials, to prepare and test a photoelastic model, and to make an experimental estimate of its behavior in static or dynamic conditions. Thus, we can analyze the processes of fracture of the rock near various openings with various cross-sectional shapes. In the elastic formulation the problems for unsupported workings have been studied comparatively thoroughly and their results in each particular case must be used, without even appealing to new experiments. For problems which do not yet posses photoelastic solutions, it is necessary to carry out additional experiments, and from their results to construct stress diistributions, mainly on the periphery of a working. As a result of an analysis of models and from our knowledge of the limiting strength characteristics of actual rock, we can predict the regions of possible loss of stability and fracture of themore » rocks, and can indicate the beginning and sequence of development of inelastic deformation of a working. According to the views advanced in this article, the failure of a homogeneous isotropic rock mass, which occurs by propagation of cracks in it, is always confined to the points of maximum stress concentration.« less