Rock response characteristics in the area of the hidden collapse column induced by mining

Abstract

The hidden collapse column has the characteristics of concealment, suddenness and connection with karst water, which pose a serious threat to safe production in coal mines. In this study, a numerical model of collapse columns with a random distribution of pores was constructed by a finite difference calculation program. Numerical simulation analyses of the coal mining face advance were carried out to explore the response characteristics of rock in the collapse column area under the influence of four factors: mining impact, lateral pressure coefficient, pore water and confined groundwater. The results show that the abutment pressure reaches its maximum when the working face advances to the boundary of the elastic stress elevated zone of the collapse column. The plastic zone above the collapse column shows a "Λ" shape and keeps growing during the advance of the working face. The height of the plastic zone in the top and bottom of the coal seam increases with the increasing lateral pressure coefficient. An increase in the lateral pressure coefficient can amplify the effect of mining on the vertical displacement and plastic zone distribution of the collapse column. When the collapse column is connected to the confined groundwater, the pore water pressure will increase significantly with the advancement of the working face. Under the joint action of confined groundwater and pore water, the extent of the plastic zone around the collapse column will be larger, and the development of the plastic zone inside the collapse column is especially obvious. This study will provide a basis for revealing the rock response rules in the area of the hidden collapse column during mining.