Face stability analysis of a shallow square tunnel in non-homogeneous soils

An improved approach for the face stability analysis of shallow square tunnels in non-homogeneous soils is investigated in this study. Based on the discrete technique, an improved 3D failure mechanism is proposed to investigate the face stability of square tunnels by incorporating the soil arching effect in the framework of the limit analysis theory. To better assess the stability issue, the non-homogeneous frictional angle phi is also considered when calculating the critical support pressures. The results obtained from this study are validated by those from the 3D finite element limit analysis and an advanced wedge-prism model based on an existing research on the limit equilibrium method.