Study on evolution law of fault stress field in coal measures at different fault dips

In order to further understand the evolution characteristics of stress field in fault tectonic zone of coal measures, taking Shihao Coal Mine in Chongqing as an example, the failure mode and internal stress variation law of faults with different dips under horizontal stress were studied by physical similarity simulation. At the same time, the influence of stress-concentrated area and fault failure at different dips was analyzed by combining with numerical simulation software PFC. The results show that sliding failure occurs when the dip of fault is small. With the increase of dip, the stress at both ends of the fault cannot slip unloading, and the failure form gradually changes to shear failure. The stress concentration occurs in footwall area of fault during loading, and the increase of dip will make the stress-concentrated area transfer from footwall seam area to footwall floor area due to different failure forms. Through PFC numerical simulation, internal cracks can be effectively observed, which not only has a good agreement with the physical experiment, but also investigates the internal microcracks of specimens. Through force chain analysis, it is found that the change of fault dip will induce the stress-concentrated area to transition from coal seam to roof and floor with strong mechanical properties.