Stress distribution under coal pillars in the case of multi seam mining: A case study at Thong Nhat Coal Mine, Vietnam

Abstract

The presence of an overlying coal pillar (OCP) strongly influences the stress distribution and deformation of the surrounding rock of the roadway and working face. In this paper, the stress distribution characteristics under the coal pillar are analyzed through numerical simulation using the FLAC3D program. Multi-coal seam mining conditions at Thong Nhat coal mine were selected as the technical foundation. Research results show that the presence of coal pillars acts as a bridge to transfer loads from the roof rock strata to the floor, and therefore it forms a high-stress concentration zone with an oval shape under the coal pillar. Caused by stress superposition, abutment stress distribution rules are affected by the distance from the roadway or working face to the OCP. In the concentrated stress zone of the OCP, the abutment pressure at the roof and floor of the roadway increases by 2 times and puts the road into a dangerous deformation condition. Meanwhile, when the working face approaches the OCP, the front abutment pressure value increases 1.3 times, and the range of the high-stress zone increases 2 times. Thus, the presence of OCP has changed the stress distribution law in the direction of increasing the value and distribution range of the maximum stress area, and it affects the roadway and working face of the coal seam below. The research results of this article will be an important document as a basis for researching technical solutions to meet the requirements for safe mining in underground coal mines.