Analysis Of Anti Sliding Stability Of Rock Slope Based On Finite Element Residual Shear Force Transfer Method

There are a lot of natural slopes in China, because of the existence of a large number of mountains, And with the implementation of road, railway, mine,dam construction and other infrastructure projects in recent years, a large number of artificial slopes emerge, that make the slope stability problems become increasingly prominent.In the course of geological activities, the discontinuous faults, joints and weak dissection appear in large rock slope under the influence of diagenesis, structure and other effects which change the slope of the mechanical characters and put forward severe challenge to the stability of rock slope. Due to the diversity and complexity of the external environment,analytic methods have not been unified standard about sliding stability of rock slope. A large number of engineering example show that the critical slip surface of rock slope often formed by a variety of interconnected discrete weak inter-layer, so the impact of weak structure plane must be fully considered in rock slope stability analysis.In this paper, in order to solve the problems that happen in common engineering, the finite element residual shear force transfer method which combines the rigid limit equilibrium method with the finite element method is proposed and suitable for mansard critical slip surface. The problem of rock slope anti sliding stability that weak structural plane does not penetrate to thesurface resulting in the main anti sliding surface position unknown is studied by the finite element residual shear force transfer method. Finally, searching the precise location of main anti sliding surface with the self compiled Fortran program. Specific contents are as follows:1. The principle of finite element residual shear force transfer method is presented: Taking into account that the internal stress transition of the slope can be shown by the change of sliding force and anti slide force of the sliding surface, the problem of slope failure can be generalized to the limit equilibrium problem of sliding surface force. The analysis process includes stress calculations and limit equilibrium slip surface analysis.(1)The slip surface force calculation: In order to study on the complexity of rock mass structure and rheological properties of material strength, the slope model is established and the elastic plastic analysis is carried out to obtain the initial stress field of the slope by using the finite element software ANSYS. The sliding force and anti sliding force of slip surface in natural are obtained directly by stress integral method based on ANSYS that fully consider the influence of cohesive force and internal friction angle of sliding surface.(2) Limit equilibrium analysis: Residual shear transfer pass down along the slip surface step by step, which is generated by assume each slip surface reaches the same state of limit equilibrium. Establishing limit equilibrium equation for each sliding surface and the safety factor of the sliding surface is obtained when the whole sliding surface reach in the limit equilibrium state after several tentative calculations, which absorbed the idea of rigid limit equilibrium method.2. The finite element residual shear force transfer method is compiled into Fortran program, which can study the slope stability influence of the main anti slide starting position and angle and find the main anti slip surface that makes the slope safety coefficient reaches the minimum value.Finally the accurateposition of the slope critical slip surface can be found out.3. Different methods were used to compare the findings: The results calculated by finite element residual shear force transfer method and finite element strength reduction method are similar. But the results calculated by finite element residual shear force transfer method is more objective and unique that overcomes the influence of the reduction method and the artificial judgment of catastrophe point. The safety factor is larger than that calculated by finite element stress algebra sum method but avoid the unreasonable problems that algebraic sum of the vector force. The safety factor is smaller than that calculated by the finite element residual thrust method, but it is more reasonable when thinking about the ways in which the balance of the force is built. The finite element residual shear force transfer method overcomes the shortcomings that calculate sliding surface force by rigid block division when compared with the imbalanced thrust force method.4. The program high efficiency calculation function are used to change the weak inter-layer material parameters and study on the change rules of safety factor and main surface position that influenced by cohesion c, internal friction angle ? and Poisson’s ratio ? of the weak inter-layer. Finally some certain rules are found out.In this paper, the calculation results of the finite element residual shear force transfer method are reasonable and reliable. It can provide a reference for rock slope stability analysis, and need to be applied and improved in practical engineering.