Dynamic and static investigation of water-conducting fracture zone in weakly cemented strata of western China: Field-monitoring-based study

Abstract

The ecological environment of Western China is inherently delicate. Post-coal extraction, forming a water-conducting fracture zone (WCFZ), poses challenges for mine water management and exerts negative pressure on the ecological balance. The traditional methods for detecting WCFZ exhibit limited applicability in the Jurassic weakly cemented strata of the Hami mining area in Xinjiang, China, owing to their short diagenetic history, high clay content, and strong water sensitivity. This study proposes a dynamic-static integrated detection method for the development patterns of WCFZ in weakly cemented strata, combining Brillouin optical time-domain reflectometry (BOTDR), borehole TV imaging, and borehole water injection testing. Field measurements were conducted to investigate the WCFZ evolution in weakly cemented strata in Xinjiang, while laboratory experiments were performed to analyze the self-healing characteristics of fractures under stress recovery and hydro-mechanical interactions. The results indicate that the WCFZ height in 11701 working face ranges from 144.16 to 152 m, exhibiting a "rapid ascent followed by dynamic descent" trend due to intense mining-induced disturbances. Validation through borehole television imaging, transient electromagnetic method, and borehole water injection test confirms the reliability of BOTDR for dynamic monitoring in weakly cemented strata. Laboratory experiments reveal that the time-dependent reduction of WCFZ height is governed by stress recovery and the swelling and detachment of clay minerals. This research provides critical references for real-time monitoring of WCFZ, water hazard prevention, and water-preserved coal mining in weakly cemented coal mining areas under similar conditions.