Abstract: A new slope stability evaluation method is proposed to evaluate the stability of excavation slope accurately and rapidly based on a small amount of indoor and field tests during initial survey. On the basis of the upper bound theorem of limit analysis, a two-dimensional limit analysis expression for the stability of excavation slope under undrained condition is derived. Tables and diagrams of stability coefficient and the variation of sliding surface under undrained condition are obtained and analyzed according to the calculation result. Finally a method of evaluating the stability of excavation slope under undrained condition is established. Results indicate that the relations between stability coefficient and undrained strength ratio, sliding surface and controlling depth can be quantified by upper bound theorem of limit analysis, which is of definite physical meaning and high calculation precision. Compared with limit equilibrium method and numerical analysis method, limit analysis method is more suitable for the evaluation of excavation slope’s stability.

Key words: excavation slope, limit analysis, stability coefficient of slope, undrained shear strength, sliding surface, limit depth