Influence of normal faults on the physical and mechanical properties of coal and the distribution of underground pressure

Abstract

Through the observation of micro fractures and pores, the mechanical experiment and numerical simulation,it is systematically revealed the influences law of normal faults on the physical and mechanical properties of coal and the distribution of underground pressure. The test results indicate that coal (rock) mass in fault zone and its influential range is broken. The closer to fault plane, the more fractures in coal (rock) mass and the less mechanical strength of coal (rock) mass are. The mechanical properties of fractures change from extension to tension shear, and from tension shear to compression shear, then in turn to extension towards fault plane. The fault induces changes of initial stress field and additional stress in some areas. The fault activation is induced during coal mining. The abutment stress ahead of working face obviously increases and the peak value position of abutment stress migrates to the inside of coal mass with reduction of distance away from the fault. The pressure distribution which acts on the pillar between the coal wall of working face and the frontal fault, is similar to the residence pillar that the peak value of pressure appear at the middle of pillar. And the thinner the pillar, the bigger the peak value is, the coal compressive strength is the limit of resident pillar abutment pressure.