Study on the minimum safe thickness of water inrush prevention in karst tunnel under the coupling effect of blasting power and water pressure

The water-filled karst cave in karst area as the disaster source is the energy storage structure of water and mud inrush disaster. Under the strong disturbance and high water pressure of blasting excavation, the water-bearing cracks in the rock mass between the disaster source and the tunnel face evolve to form water inrush channels, resulting in major disasters. In this paper, according to the type of water inrush caused by progressive failure of water-resisting rock mass, the outburst prevention structure is divided into disturbance failure zone, seepage failure zone and spallation failure zone. Based on the theory of rock mass mechanics, fracture mechanics and explosion mechanics, the water-rock interaction mechanism of drilling and blasting tunnel is analyzed, and the calculation method of minimum safety thickness of outburst prevention structure is established. Through the example verification of 2 # pressure pipeline project of Dagangshan hydropower station cavern group, the minimum safety thickness of anti-outburst structure in water inrush project is determined to be 5.25 m.