Stress Distribution Characteristics Near Small Coal Faults and Prediction of Coal and Gas Outburst Risk

Abstract

This study aims to accurately predict the risk of coal and gas outbursts in coal seams located near small faults. Models of small-scale normal faults in the Changping mine field were constructed using the FLAC3D software, with fault dip angles of 65° and 70°, and drops of 1, 3, 5, 8, and 10 m. The objective was to analyze the effects of fault drop and dip angle on stress distribution near the faults and to predict the related outburst risks. The results indicate that in the hanging wall of the fault, the peak stress correlates with the fault drop through a linear function, whereas the range of influence is described by a quadratic function. As the fault drop increases, the impact range and stress peak also increase. The position of the stress peak gradually shifts away from the section, whereas the stress concentration area widens. Furthermore, the protruding danger zone expands and similarly moves farther from the section. When the fault drop is constant, the impact range of the 65° dip fault is smaller; however, the stress peak and the stress concentration zone in the nearby coal seam are larger and closer to the fault surface. Additionally, the highlighted danger zone is also larger and nearer to the fault surface. On the basis of the measured fundamental parameters of coal seam gas in the region, within a distance of 6 m from the fault surface (Zone I), there is a significant influence from the fault, resulting in a higher risk of outburst in this area. In the range of 6–15 m from the fault surface (Zone II), the gas content continues to increase, leading to an overall heightened risk of outburst.