Once a soil slope is led to the limit equilibrium state by means of the finite element – strength reduction technique

usually

the critical slip surface goes through the points at which the equivalent plastic strain takes the maximum. First

some vertical lines are arranged along the horizontal direction. Then

along each of the vertical lines the point with the maximum equivalent plastic strain is found out. All such points compose a wave and make up the functional data. Finally

the functional data are smoothed by the least square method and the position of the critical slip surface is determined. The proposed procedure is confirmed through the comparison with other mature methods.