A main factor affecting the rationality of the sloped foundation stability analysis is to determine the position and shape of the sliding surface。Therefore the first problem of the sloped foundation stability analysis to be solved is to reasonably determining the position and shape of the sliding surface. The Mohr-Coulomb yield criterion

commonly used in the geotechnical engineering

shows that the failure of the rock and soil mass is due to the reach of the shear stress on someone surface to its shear strength

when there must occur a large shear deformation on the shear plane. Therefore

the sliding surface can be determined through searching the positions where have the largest shear strain increment. Based on the ideas above

comprehensively using the finite difference software-FALC3D and the curve fitting technique

the paper proposes a method

based on the largest shear strain increment

to determine the potential sliding surface. Its specific processes steps are that: firstly

the stress and strain in the slope are calculated by using the finite difference software-FALC3D; then a series of vertical line would be set in the calculating section

and then the discrete coordinates of the sliding surface

where the shear strain is largest on the vertical line

would be found through programming FISH program. Then the position and shape of the sliding surface can be obtained through carrying out the curve fitting of the discrete points by using the least squares method. The rationality of the proposed method is verified through comparatively analysing the limit equilibrium method. The method has a criterion with clear physical significance and is simple

convinient and practical for application and also overcomes the dependence of the calculting grid.