Abstract: The incremental linear elastic model with modulus of deformation E and poisson’s ratio is very popular in numerical analyses of soil engineering. To research and understand the effects of E and on calculation of FEM is helpful to analysis of calculation results. Firstly, one parameter was simply assumed to keep a constant and effects of variation of another parameter were analyzed. Secondly, when the stability of slope was evaluated with FEM, the effect of E and had already been considered in strength reduction technique. The following three conditions are jointly used as a criteria to assess stability failure of slope, the contour lines of ? xy formed a sliding surface stress levels S in elements on sliding surface equaled to l and the displacement at a certain node increased suddenly. Thirdly, relationships between E and were discussed by means of strength parameters, the greater the E, the greater is the strength and the less is the of soil.

Key words: strength reduction technique, FEM, modulus of deformation, Poisson’s ratio, safety factor