Influence of fracture structure plane on underground pressure and roof stability of working face

By using field observation and numerical simulation method, the influence of fracture structure plane on the underground pressure and the roof stability of working face are systematically studied.The research results show that the fracture structure plane of coal roof has three kinds of typical combination styles,namely "regular triangle" structure,"Ⅲ shape" structure and "inverted triangle" structure,During coal mining,the coal roof of "regular triangle" structure is unstable,but the "inverted triangle" structure is stable and the roof of "Ⅲ shape" structure is able to form structure equilibrium and reaching stability.Because of fault inducing medium discontinuous and changes of initial stress field and additional stress in some areas,there are the low stress area and high stress concentration zone in the fault and its surrounding zone,the much obvious effect range is about 10~30 m far away the fault surface.In the high stress concentration zone of fault,the abutment stress in front of working face increases obviously and the peak value position of abutment stress migrates to the inside of coal mass with reduction of distance away from the fault.In the zone,the roof accident and other dynamic phenomenon are prone to happen.In the low stress zone of the fault,the strength of coal and rock is lower,the abutment stress decreases and the stability of coal roof is weak.