STUDY ON THE UPPER BOUND SOLUTION OF SUPPORTING PRESSURE FOR SHIELD TUNNEL FACE SUBJECTED TO PORE WATER PRESSURE

Based on the upper bound theorem and spatial discretization technique, an upper bound failure mechanism for a shield tunnel face that can be applied to saturated stratum was established. By regarding the work rate of pore water pressure as an external loading work rate, the effect of pore water pressure is introduced into the virtual work rate equation of the upper bound theorem, and the upper bound solution of supporting pressure for tunnel face subjected to pore water pressure was obtained by optimizing calculation. To evaluate the validity of the upper bound solutions, the ultimate supporting pressures for tunnel face subjected to pore water pressure were computed by numerical simulation. The numerical solutions were compared with the upper bound solutions. The comparing results show that the upper bound solutions are very close to the numerical solutions. Finally, the influence of parameters variation on the upper bound solution and the failure surface of the tunnel face was studied. The parametric analysis demonstrates that pore water pressure has significant influence on the upper bound solution of supporting pressure while it has slight influence on the range of failure surface of tunnel face.