Stress control for coal and gas outburst on a fault plane

A mathematical model is developed to describe the stress state of a fault plane. The control factors for coal and gas outburst near the fault are identified using the relationship between section normal stress and shear stress. The sealing coefficient is redefined and the concept of shear index is introduced to judge sealing ability of the fault and its structural stability. The study shows that the magnitude of normal stress is positively correlated with the acute angle between the fault strike and the maximum horizontal principal stress. However, it is not always between the magnitude of shear stress and the acute angle, which depends on the maximum/minimum horizontal principal stress and the normal stress. When certain intensity is satisfied, the gas pressure is a premise condition for the coal and gas outburst near the fault. Combined with the deformed coal distribution, according to the restrict relationship between gas pressure and normal stress in the fault, the coal and gas outburst are classified into 2 types: flow pressure controlling (FPC) and fluid solid coupling (FSC). An engineering case is employed to validate the stress control for the coal and gas outburst on the fault plane.