Research On Mechanism Of Coal And Gas Outburst Induced By Mining Instability In Hanging Wall Of Normal Fault

Coal and gas outburst is a complex geodynamic disaster that occurs during the production of coal mines and seriously threatens the safe production of coal mines.Statistics show that the number of outbursts near the fault accounts for more than 40%of the total number of outbursts,mainly occurring in the normal fault’s hanging wall.In this study,through theoretical analysis,numerical simulation,and physical experiment,the mechanism of fault structure instability and induced outburst under the influence of mining on the hanging wall of normal fault are deeply studied,and the causes of frequent outburst accidents on the hanging wall of normal fault are discussed.The main research results are as follows:(1)Based on the mechanical analysis of the formation process of normal faults,the mechanical differences between the two plates are compared,and the fracture distribution,permeability change,and tectonic coal development law of the two plates are studied.The results show that the fracture and tectonic coal of the coal-rock mass on the hanging wall of the fault are more developed in the same coal-rock strata.Coal’s mechanical strength and permeability near the normal fault are low.(2)According to the different sliding states of the fault,fault instability is divided into two types: fault local instability and fault slip instability.Based on the effective stress analysis of the fault plane,the mechanical model of the hanging wall instability of the normal fault is established,and the mechanical criterion of the hanging wall instability is proposed.(3)The mechanism of mining instability in the hanging wall of normal fault is expounded from the perspective of stress and energy.Through the numerical simulation of step-by-step excavation and the physical simulation test of outburst,the distribution characteristics of stress and pore pressure on the two walls of the normal fault and the activation and instability law of normal fault are studied,and the above mechanism is verified.(4)Combined with the ‘11.25’ outburst case of Sanjia Coal Mine,the mechanism of coal and gas outburst induced by mining instability on the hanging wall of normal fault is further revealed.The gas-solid coupling model of normal fault hanging wall excavation is established.The changes in coal stress,elastic energy,and permeability in front of the working face before and after excavation are compared.The influence of fault zone permeability and tectonic coal development degree on gas migration is analyzed.