Design equations for undrained stability of opening in underground walls

Undrained stability of an opening in underground walls in clays with constant and linearly increasing shear strengths with depth was investigated by two-dimensional finite element limit analysis under plane strain condition. Three parametric studies were performed to study the effects of the cover depth ratio, overburden stress factor and linear strength gradient ratio on the load factor of the opening in underground walls. Predicted failure mechanisms associated with these parameters were discussed and examined. New design equations for the undrained stability of an opening in underground walls in clays with an arbitrary linear increase in strength with depth were developed for a practical application in the field of trenchless constructions.