Dynamic evolution characteristics and prediction of water inflow of karst piping-type water inrush of tunnels

A model for karst piping-type water inrush at tunnel site is established, and the dynamic evolution characteristics of water inrush are analyzed. The results show that there is no obvious time effect for the dynamic evolution of karst piping-type water inrush, but the spatial features have the property of phase evolution. The water inrush area can be divided into three typical flow velocity evolution areas: approximate high-velocity stability zone inside the karst pipeline, velocity rising zone near the critical plane and attenuation-low velocity stability zone in the tunnel. Based on the dynamic attenuation law of flow velocity in the inner area of pipeline, the method of limit analysis combined with numerical methods to predict water inflow is put forward, and a prediction system for water inflow is formed. The corresponding model test is designed, and the real-time monitoring of water inflow is carried out. The rationality of the comprehensive prediction method for water inflow is verified.