Development height of water-conducting fracture zone in fully-mechanized caving of extra-thick coal seam under strong aquifer

Investigating the height of the water-conducting fracture zone is pivotal for mitigating roof water hazards, particularly under the challenging conditions of fully mechanized top coal caving mining in extra thick coal seams beneath strong aquifers. Set against the backdrop of the ZF1405 working face in the Yadian Coal Mine within the Binchang mining area, this study employed a multifaceted approach. By combining multiple nonlinear regression, numerical simulations, and borehole measurements, it developed a robust predictive model for the fracture zone's height. The findings underscored the significance of considering a wide array of influencing factors to enhance the model's precision, with the predicted height reaching 257.4 m-markedly more accurate than traditional empirical methods suggest. The maximum development height of the water-conducting fracture zone obtained by numerical simulation is 244.2 m. The evolution of the fracture zone was delineated into three distinct stages: a gradual increase observed up to 200 m of working face advancement, followed by a sharp rise between 200 and 280 m, culminating in a stabilization phase beyond 280 meters. This sharp increase phase was particularly prone to roof water inrush incidents, highlighting the need for advanced preventative measures beyond the 200-meter mark. The model's reliability was further corroborated by the convergence of numerical simulation outcomes and borehole observations, which recorded the water-conducting fracture zone heights at 247.4 m and 238.4 m, respectively. Opting for the maximum value of 257.4 m as a conservative estimate, this research provides a solid foundation for predicting the height of water-conducting fracture zones in mines under similar conditions. © 2024 Editorial Office of Journal of Mining and Strata Control Engineering. All rights reserved.