Evolution of runoff discharge patterns and risk assessment of water inrush in mountainous railroad tunnels

Mountain railroad tunnels often need to cross deep and large active fracture zones during construction and tunnel site areas can be crisscrossed with underground water systems that carry huge volumes of water. The risk of sudden water inrush during the construction of mountain railroad tunnels is high, and uncontrolled inrush water runoff can negatively impact the tunnel site area. Therefore, risk assessments and prevention of inrush related surface runoff damage is key to reducing the ecological impact of tunnel construction. In this paper, the inrush water runoff of a typical mountainous railroad tunnel in the southwest of China was taken as the research object and the hydrological model and hierarchical analysis (AHP) were used to build a comprehensive risk assessment algorithm for surface runoff. Then the risk level of each section of the runoff channel was assessed under different flow scenarios and different inrush water runoff environmental risk prevention measures were proposed.