Geological evolution process, mechanism, and application of protective layer in semi-coal and rock face

Xiaoping Xie,Xinqiu Fang,Minfu Liang,Dechun Ai

doi:10.15446/esrj.v24n4.91378

Abstract

Under the influence of geological structure, the surrounding rock of semi-coal seam is easy to be loose and fractured, and the repairing rate is high. Therefore, it is of great theoretical and practical significance to study semi-coal seam mining's mechanism and control technology. In this paper, the geological evolution principle of the semi-coal seam is analyzed theoretically. The mechanic's relationship between the mining height of the semi-coal face and the lower coal seam's pressure relief is interpreted. The mechanism of eliminating bad blind areas in non-pillar mining of upper protective seam is analyzed. Through numerical simulation analysis, it is concluded that the expansion deformation rate of a protective layer increases linearly with the increase of mining thickness of the protective layer, and the width of undesirable blind zone of coal seam increases linearly with the rise of protective layer thickness. This paper puts forward the technology of non-pillar mining in the protective seam's semi-coal and rock face. Field industrial test results show that the technology achieves the overall pressure relief and reflection reduction of low permeability and high gas coal seams. The underlying 3 + 4 protective layer achieves the general pressure relief and reflection reduction of low permeability and high gas coal seams. Coalbed methane can be pre-drained up to 18 m3/min with a concentration of 90%.

Highlights

When the roadway excavation section has both rock and coal seam, and when the coal seam occupies 1/5 to 4/5 of the area of the excavation face, it is called semi-coal-rock mining working seam, which generally exists in thin coal seam conditions
After the semi-coal rock working face is mined, the load of overlying strata in goaf is transferred to the front of coal wall forming an abutment pressure, and the coal wall is in a plastic or fracture state within a certain depth (Zhou et al, 2015; Cheng et al, 2012)
After the length of two working faces is continuously mined in the direction of inclination of 150 m, non-coal pillars are left between the two working face interfaces and the width of the pillar of the section is left separately

Summary

Introduction

When the roadway excavation section has both rock and coal seam, and when the coal seam occupies 1/5 to 4/5 of the area of the excavation face, it is called semi-coal-rock mining working seam, which generally exists in thin coal seam conditions. Geological evolution process, mechanism, and application of protective layer in semi-coal and rock face.

Results

Conclusion