Safe Range of Retaining Pressure for Three-dimensional Face of Pressurized Tunnels based on Limit Analysis and Reliability Method

Based on the existing research, the 3D active and passive failure mechanisms of a pressurized tunnel face are constructed. The nonlinear failure criterion is introduced into the limit analysis by virtue of the tangent technique. By neglecting the randomness of soil parameters, the collapse pressure of active failure and the blowout pressure of passive failure, namely the lower and upper limit of retaining pressure, are obtained along with the failure ranges. On account of the randomness of soil properties, a three-dimensional stochastic model of a pressurized tunnel face is established, and the optimal range of retaining pressure of the pressurized tunnel face is presented on the basis of the multiple correlated failure modes. Taking Changsha Metro Line 2 as an example, the good agreement of the measured data in situ with the reasonable range of retaining pressure verifies the presented method. The combination of limit analysis and reliability method can provide more scientific and reasonable support parameters for the construction of pressurized tunnels in the future.