Abstract: The three-dimensional general slope and steep slope as numerical models are used to research the inhomogeneous slope reduction scope by the field variables based on finite element strength reduction method. In the study, from some scholars research results, both rock material’s shear strength parameters and tensile strength parameter T are reduced in ABAQUS. In light of the current shortage in existing slope stability criterion, the point mutant which sites on the relationship curves between the ratio of the feature point displacement’s increment to the strength reduction coefficient’s increment and the strength reduction factors is applied to determine the critical state of slope. The results show that the reasonable safety factor can be obtained only when the local reduction in the cohesion of similar circumstances is implemented and suggests that the overall strength reduction can be used for the rock mass difference slope, whereas the more reliable results can be obtained for the relatively soft local reduction in the high and steep three-dimensional slope. Compared with the traditional feature point displacement criterion, the (the relationship between feature point displacement increment and the strength reduction coefficient increment ratio and strength reduction factor) method is proved to be practical and reasonable. Meanwhile, the safety coefficient of bridge foundation is calculated based on the criterion, so as to provide a theoretical basis for the control of the bank slope.

Key words: three-dimensional bridge foundation slope, strength reduction method, inhomogeneous slope, instability criterion, safety factor