Theoretical Analysis on Safety Thickness of the Water-Resistant Rock Mass of Karst Tunnel Face Taking Into Account Seepage Effect

We took into account the adverse influence of karst water seepage effect on water-resistant rock mass tunnel face. Based upper-bound theorem limit analysis and Hoek–Brown failure criterion, we obtained calculation method critical safety thickness mass. carried out a feasibility analysis, an influencing factors comparative with previous related research achievements this method. The results showed that: (1) With decrease surrounding grade, gradually increased, at all grades remained within reasonable range. (2) decreased as compressive strength, tensile strength parameter A it increased pressure, excavation height, B increased. (3) change trend was completely consistent under two conditions considering without effect, force greater than that force. Taking Yunwushan Tunnel Yiwan railway example, calculated value in good coincidence adopted actual project. are great significance to prevent occurrence high pressure filling geological disasters such inrush tunnels.