Permeability Failure of Filling Medium in Fault Fracture Zones

This study established an erosion weakening model for the strength degradation of filling media, the rationality and validity of which were verified via indoor particle loss tests. To study the engineering-scale disaster evolution, fluid–solid coupling numerical simulations were conducted, with the water inrush in the Paomashan No.2 Tunnel used as the engineering case study. Simulations reproduced the catastrophic permeability failure, further validating the accuracy of the proposed model. Orthogonal numerical simulations with fault width, dip angle, constant water pressure, and tunnel excavation height as variables revealed the evolution laws of mud–sand volume and inrush morphology. The study also included a classification of the severity levels permeability failure-induced inrush in fault fracture zones and importance raking of influencing factors. This study deepens our understanding of the evolution mechanism of permeability failure in fault-filling media and provides important technical support for the prevention and control of such engineering disasters.