Mathematical Modeling of Stress-Strain Evolution in the Rock Mass around a Mine Opening. Evaluation of the Steps of First Roof Caving at Different Thicknesses of the Main Roof

Abstract

Intensive mining activity has highlighted the need to study the dynamics of rock mass elements and to assess the degree of their nonequilibrium. The roof, floor, pillars, gateways, and so on are in a highly nonequilibrium state due to difficult mining conditions and high face advance rates. A good tool for predicting the mechanical behavior of the rock mass during mining is mathematical modeling, which is based on the solution of dynamic problems taking into account the nonequilibrium and nonstationary deformation and failure of rocks. In this paper, dynamic modeling has been performed within an evolutionary framework to investigate the steps of first caving in a model rock mass during face advance. All other things being equal, the thickness of the main coal seam roof is varied in the calculations. The steps of first caving are evaluated in the conditions of highly nonstationary deformation of the rock mass. The fluctuation statistics of the stress-strain parameters of the rock mass is analyzed. It is shown that the first roof caving is preceded by a fall in the slope of the amplitude-frequency curve of stress fluctuation.