Seepage-Stress Coupled Analysis on Shield Tunnel Face Stability in Layered Soil

Shield tunnel face stability in layered soil is becoming the important problem on the underwater. Seepage-stress coupled on the tunnel face is analyzed using fast Lagrangian method and discussed the effect of seepage force on face stability, and the relation is analyzed between the face pressure and the deformation of tunnel face. According to the stability theory, the limit support pressure that displacement of the center at tunnel face increases large suddenly when face pressure is changed very small is compared with the result of reference [7] by wedge body limit equilibrium, the error is only 5.7% and reasonable. The support pressure provide convincing computing results for the minimum pressure of tunnel face in design and construction and the support method to prevent the collapse of tunnel face. Comparing the plasticity, stress, displacement of the tunnel face under seepage force, it is showed that seepage-stress coupled has a bad effect on the stability of tunnel face, the support pressure is equal to the total of the effective face pressure and seepage force and the seepage force is the most of the total support pressure. The influence of pore water pressure on the stress and displacement and stability of tunnel face is large and not ignored. By comparison of coupling of fluid-solid effect, it is found the seepage force is the most of the total face pressure and the exist of underwater has the disadvantage influence on stability of tunnel face and not ignored.