Influence of permeability anisotropy of seepage flow on the tunnel face stability

This paper focuses on the influence of permeability anisotropy of seepage flow on the face stability for a shied tunnel. An analytical model has been proposed to present the hydraulic head distribution around the tunnel face in the anisotropic ground, considering the difference of permeability coefficient in the horizontal direction and the vertical direction. The rationality of the proposed model is verified by a series of numerical simulations. Then, an analytical model of face stability for a tunnel under the anisotropic seepage has been established based on the limit analysis upper bound method. Comparisons of the analytical solutions and the numerical simulations are conducted, and the limit support pressure of the two methods is consistent. The effect of permeability anisotropy and water pressure on the stability of the tunnel face is analyzed through the three-dimensional analytical solution. Anisotropy of permeability has a significant impact on the stability of the tunnel face, and its impact gradually decreases. It can also be found that the water pressure coefficient of the tunnel face has a significant effect on the limit support pressure and the failure area when the ratio of the horizontal permeability to the vertical permeability is large.