Evolution Patterns of Water−Guiding Fracture Zones Due to Repeated Mining in Close−Bearing Coal Bed Groups and Measures for Water Control

Located in the Jurassic coalfield of northern Shaanxi, Liangshuijing Coal Mine exhibits typical conditions for close−range coal seam clusters and significant repeated mining effects. Addressing complex geological conditions—including multi−layered repeated mining, the absence of basement water barriers, and strong aquifer permeability—the study employed a combination of physical similarity modeling, numerical simulations, and field measurements to systematically investigate the dynamic evolution of water−conducting fracture zones in overlying rock during close−range coal mining. Results demonstrate that under repeated mining conditions, water−conducting fractures exhibit pronounced "activation and expansion" characteristics: mining activities cause stress redistribution in lower coal seams, activating existing fractures in upper goaf areas and inducing rapid nonlinear growth of fracture zones; complete fracture failure of inter−bedding rocks serves as a critical control point for upward fracture extension, with fracture development height showing abrupt increases after breakthrough; stable compaction phases occur between mining layers, where overlying rock fractures demonstrate self−healing capacity through gravity−induced compaction and clay swelling upon water contact, partially restoring water−barrier properties, thus forming a dynamic evolution mechanism of "development → activation → compaction closure." Based on the aforementioned evolutionary principles, a layered coordinated mining strategy was proposed, establishing a three−dimensional integrated prevention and control system for roof water hazards comprising "source control – seepage reduction – risk elimination." This approach effectively curbed the excessive development of water−conducting fracture zones, preserved the integrity of highly water−rich aquifers, and ensured safe and efficient mine operations, and provides both theoretical foundations and practical references for water−preserving mining of close−coal seams under similar geological conditions.