Modelling of Geomechanical State of the Rock Mass during the Large Scale Mining of Underground Space

Abstract

The article considers the mechanical and mathematical modeling of the process of subsidence of the Earth’s surface during the mining of rock mass by a pillar mining system. The task is to study the influence of the waste space on the state of the rock strata located at different depths (Horizons) at each stage of the process of rock movement. The purpose of the study is to develop a numerical geomechanical model of a rock mass using a pillar mining system, which makes it possible to correctly identify the characteristic zones formed as a result of mining operations in the rock column, and also provides an opportunity to simulate the process of formation of the daily surface subsidence trough. Computational numerical schemes of model problems are constructed using finite element and discrete element modeling algorithms. Based on the results of numerical modeling, it is shown that the characteristics (linear dimensions and maximum subsidence) of the subsidence trough obtained in accordance with the developed geomechanical model are close to the characteristics calculated by the engineering methodology used in the conditions of the Starobin potassium salt deposit (Republic of Belarus). At the same time, as the depths of mining operations increase, the discrepancies between them increase. The analysis of the reasons for this behavior is carried out. The nonlinear nature of the change in the boundary angles of displacement in the layers of the rock strata with an increase in the depths of mining is presented and conclusions explaining these changes are noted. The application of the obtained modeling results is to substantiate the possibility of reducing the size of the security pillars around the mine shafts and ground objects with an increase in the depths of mining operations, thereby reducing the amount of mineral reserves left in the bowels and increasing the economic indicators of extraction.

Keywords

• finite element modeling
• block elements
• coulomb–mohr model
• layered rock mass
• pillar mining system
• zone of collapse
• zone of fracturing
• boundary displacement angles
• displacement trough