The heterogeneity of soil in geotechnical engineering is relatively common

while the analysis method for the face stability of tunnel in nonhomogeneous clays is not well established so far. A simple method for evaluating the undrained stability of plane strain heading tunnel in soft clays is presented. Rigorous upper bounds on the loads required to resist collapse are derived using a rigid block translational collapse mechanism on the basis of plastic limit analysis. The variation of shear strength with depth and the gravity of soil are considered in the study. To verify the quality of the upper-bound solutions

the results are compared with those obtained from the finite element limit analysis. It can be proved that the upper-bound method of limit analysis is a feasible approach for the face stability analysis of tunnel; and it also provides an important theoretical basis for the practical geotechnical engineering.