Stress Evolution Law of Coal and Rock Mass Affected by Mining before and after Dydraulic Fracturing

Abstract

Stress concentration of coal and rock mass is the intrinsic cause of rock burst, the dynamic evolution law of coal seam stress and roof rock stress during the advancing process of mining face is obtained by using the coal seam stress monitoring system and the developed surrounding rock stress monitoring system, In this paper, the stress variation law of coal and rock mass during mining and the correlation between them are analyzed in detail. In order to reduce the danger of rock burst caused by stress concentration, hydraulic fracturing measures of roof strata were adopted in the field, and the stress changes of coal and rock mass before and after hydraulic fracturing were compared and analyzed. The results of the inspection show: The vertical stress gradient is linearly correlated with the trend of coal seam stress. The influence of mining on the stress of rock seam is earlier than that of coal seam, but the influence of mining disturbance on the stress of coal seam is higher than that of rock seam; The increase amplitude of vertical normal stress of roof strata under mining disturbance is obviously higher than that of two horizontal stresses; the stress value of coal and rock strata decreases after hydraulic fracturing, and the decrease amplitude of stress in coal seam is larger than that of rock strata after hydraulic fracturing. The peak stress of coal seam moves toward stopping line than that before hydraulic fracturing. Field application shows that the stress evolution information of coal seam can provide the corresponding basis for anti-scouring measures and ensure the safe and efficient production of working face.