Upper Limit Analysis of Tunnel Collapse Under Existing Pipe Gallery Based on Hoek-Brown Strength Parameter

In addressing potential challenges stemming from the passage of subway tunnels beneath existing pipe gallery, the collapse failure mechanism of the stratum above the tunnel was constructed within the framework of upper bound theorem.This considered the synergistic effect of the structural load and supporting force of the upper pipe gallery.Based on the Hoek-Brown strength criterion of GSI method and the associated flow law, the analytical solution of the collapse slip surface was derived, and the formula for calculating the critical distance between the tunnel roof and the pipe gallery floor was given.The theoretical results were compared with the numerical solutions, and the agreement verified the correctness of the present method.The effect of different parameters on the collapse failure range and the sensitivity of each factor were discussed, and the corresponding engineering suggestions and measures were given.The research results could provide some theoretical guidance for the design and construction of tunnels under such working conditions.