Upper bound analysis of surrounding rock pressure in shallow buried unsymmetrical tunnels based on the Hoke-Brown criterion

Abstract

Tunnel stability is mainly concerned with the object of symmetric tunnels, shallow buried unsymmetric(SBU) tunnels should also be emphasized as the focus of the computational analysis of tunnel engineering. It is especially important to solve the expressions of ultimate support force and damage surface function for SBU tunnels. In this paper, considering the effect of unsymmetrical action, based on the Hoke-Brown(H-B) damage criterion, the optimal upper bound(UB) solution expression is derived by using the limit analysis method. The expression can be used to express the support force and collapse pattern of a SBU rectangular tunnel. The results show that q1 and q2 decrease with the increase of parameters A and σc, and increase with the increase of parameters B, γ, and h. q1 increases with the increase of α, and vice versa for q2. The range of damage surface decreases with increasing parameter A, σc and increases with increasing parameter B, γ, d, h. After the feasibility study and results analysis, it is concluded that the results obtained in this study are consistent with common engineering knowledge. The training results using Feedforward neural network verify the feasibility of the method for SBU tunnels and can be generalized for shallow buried(SB) symmetrical tunnels. The proposed method can provide a theoretical basis for the support design of SBU tunnels.