Water Inrush Mechanism Caused by Fault Activation Based on Stress Evolution of Surrounding Rock of Key Aquifer

Abstract

Water inrush accidents in coal mines are becoming increasingly serious with the increase in mining depth. Among these accidents, water inrush caused by fault activation is the most common. The water inrush mechanism cannot be revealed by the traditional method in determining whether the fault is activated by the displacement difference between the two walls of the fault. The fault Sun of Longdong coal mine was considered a research target, and the research methods of similar simulation test and numerical simulation were used based on the mining stress characteristics of surrounding rock of the key aquifer to investigate the water inrush mechanism and main control factors due to fault activation in mining. The mining characteristics of fault zone rock mass were analyzed in the process of coal pillar reduction, and the change in water inrush risk in the process of coal pillar reduction was revealed from the surrounding rock stress state of the key aquifer. Results show that the stress transfer law is evidently different in hanging wall and footwall. The stress state of the hanging wall rock near the fault zone is dominated by the compressive stress, whereas the stress state of the footwall changes with buried depth. The stress state of the surrounding rock roof of the key aquifer and fault zone changed from compressive to tensile stress, when the width of the coal pillar was 30 m. The degree of pressure relief increases with depth, and the results obtained by the two methods are consistent. Evident shear failure occurs in the fault zone, and such failure is unfavorable for water prevention. The conclusions in this study provide theoretical basis to retain the coal pillar.