Abstract: In view of the continuous deterioration of strength parameters of rock and soil during the progressive failure of slope, the strain-softening model, instead of the traditional ideal plastic model, was applied. An improved vector sum algorithm, which considers the tensile-shear progressive failure, was proposed in this paper. Both the safety factor expression and the method of searching the most dangerous sliding surface were studied. Based on vector characteristics of sliding and force, the sliding trend and safety factor expression of vector sum were improved. Moreover, the most dangerous sliding surface of slope was searched based on the improved adaptive genetic algorithm. Results of several case studies show that, when the strain-softening model was adopted, the safety factor based on the definition of vector sum and the most dangerous sliding surface shape have dynamic changes and adjustment characteristics. The proposed algorithm in this paper, which is based on the tensile-shear strain softening model, expands analytic methods of slope vector sum to a certain extent.

Key words: slope engineering, vector sum method, genetic algorithm, tensile failure, progressive failure, strain-softening model