Evolution of Water-Conducting Fracture in Weakly Cemented Strata in Response to Mining Activity: Insights from Experimental Investigation and Numerical Simulation

Abstract

The accurate prediction of the vertical extent of water-conducting fracture (WCF) zones in weakly cemented strata is particularly significant in preventing and controlling water hazards in western coal mines. The evolution of fractures in weakly cemented strata affected by mining disturbances was comprehensively analyzed by physical similarity models, numerical simulations, and field investigations. Results indicated that the development progress of water-conducting fractures can be divided into three phases: initial slow generation, subsequent rapid development, and eventual stabilization. The numerical simulation results revealed that in the initial stage of working face mining, the development of the plastic zone is limited, and there is minimal failure in the overlying strata; therefore, fractures are slowly produced without penetrating through the strata. When the plastic zone fully encompasses the entire main roof, it triggers severe shear failure in the overlying strata, resulting in rapid fracture propagation and penetration. Once the fracture height reaches a stable state, there is no further increase in the maximum vertical displacement of key strata, indicating the extensive collapse and compaction of the overburden as well as the stabilization of the fracture heights. A modified prediction equation for WCF in weakly cemented strata was obtained by correcting the traditional empirical formula based on field investigations. This modified prediction equation enhances the accuracy in predicting fracture heights and provides a theoretical reference to address the issue of the inaccurate prediction of the water-conducting fracture height in western mine rock strata.