Cataclastic deformation and alteration induced fault water inrush: Cross effect, hazard characteristics and identification method

Faults are the main adverse geological causing water inrush hazards in tunnels. The complexity and diversity of fault-induced water inrush often results in hazard response delays. This study proposes a typical hazard mode, i.e., the Cataclastic Deformation and Alteration Induced Fault Water Inrush (CD/A-WI). Integrating mineralogy, geochemistry, and microstructural analysis, this method investigates the cross effect of cataclastic deformation and alteration on the fault water inrush hazard. Microstructural analysis revealed the fault damage mechanism, while mineralogy and geochemistry clarified the surrounding rock’s alteration. The cataclastic deformation and alteration resulted in numerous fractures and fragmented breccias, creating primary fluid pathways that accelerate alteration processes. Consequently, alteration weakens the surrounding rock’s mechanical strength, intensifying rock mass failure and leading to water inrush hazards after tunnel excavation. The typical characteristics of the CD/A-WI include an abundance of breccias with cataclastic and loose structures and a notable increase in altered mineral types and contents, evidenced by microstructural elements like cataclastic flows. This mode was validated through its application in the Gaoligongshan Tunnel. The method and finding provide a basis for understanding the geological factors in tunnel hazard and offer valuable insights for designing and constructing comparable engineering projects.