ABSTRACT
In this study, two factors were considered simultaneously for assessment of tunnel face stability. The first factor taken into consideration is the effective stress acting on the tunnel face calculated according to the upper bound solution of limit analysis, and the other factor is the seepage force calculated from numerical analysis under steady state groundwater flow conditions. From the results of derivations of the upper bound solution with consideration of seepage forces acting on the tunnel face, it was found that the minimum support pressure required for the stability of the tunnel face was equal to the sum of the effective support pressure and the seepage pressure acting on the tunnel face, where the distribution of the seepage forces acting on the tunnel face are calculated through numerical analyses. Consequently, a reasonable design concept to evaluate the support pressure required for stability of the tunnel face is suggested.
