Analysis of face stability for tunnels under seepage flow in the saturated ground

Abstract

Based on the three-dimensional hydraulic head distribution model and the upper bound theorem of the limit analysis, a new model was established to calculate the limit support pressure in shield tunnel faces. A series of numerical simulations were conducted to evaluate the accuracy of the proposed model and the obtained results were compared with those of other classical analytical methods. It is found that the obtained analytical solutions are in good agreement with the numerical simulations and the proposed method outperforms other methods in terms of accuracy. In the present study, the influence of the water level, internal friction angle, burial depth, and water pressure on the stability of the tunnel face is analyzed. The performed analyses reveal that the limit support pressure is negatively correlated with the internal friction angle, while the burial depth does not affect the limit support pressure of the shield tunnel face in subsea tunnels (C/D ≥ 1). Meanwhile, it is found that as the water level and the water pressure on the tunnel face increase, the limit support pressure increases linearly, and the failure area extends to the front of the tunnel face and decreases in height.