Slope Stability Finite Element Analysis And Programming Design

Limit equilibrium method has been widely applied in engineering problems, but it doesn't include soil stress strain relationship, and makes assumptions on the inter-soil slice forces, so the result is not accurate, and it cannot provide the deformation of the slope. Finite element method can give the accurate stress field of the slope, differentiate different stress path, such as fill and excavation slopes, so it will be used more frequently. The following is the summarization of this paper.Firstly, non-circular slip surface stress finite element method is completed. Safety factor is defined along with a series of initial slip surfaces in slope stability finite element. Then stress field is obtained through FEM software, such as Geo-slope and ANSYS to calculate the safety factor. Area coordinates is introduced into the program in order to determine the stress tensor of the integration points on the slip surface. Four-node element is used here, and the scope of the element is defined by its maximal and minimal x coordinates and y coordinates. If the integration point doesn't belong to this scope, then check that for the next element. Otherwise, calculate the element area and the four triangles area. If the difference is less than the given precision, then it can be thought that the integration point belongs to this element. The element node stresses can be used to interpolate the stress tensor of the integration point. It is may be difficult to give the initial non-circular slip surface, and circular slip surface method is combined with the method of this paper to solve this problem. Sweden Arc Method can obtain the potential slip surface that quite similar to the accurate Bishop method, though the safety factor could be less than that of Bishop Method. So Sweden Arc Method is used to obtain the potential slip surface, which along with other slip surfaces near it then is regarded as the initial slip surfaces. Then the initial slip surface is discreticzed and Hooke Jeeves Method is used to search for the most dangerous slip surface with the minimal safety factor.Secondly, because ANSYS is used to calculate the stress distribution of the slopes, the constitute law parameters must be accurate. Non-assocaite flow rule based Mohr-Coulomb matched DP model in plane strain condition is deduced. Many Finite Element software such ANSYS use DP1 model as the constitute law model for the soil materials, which could overestimate the soil load capacity. Different DP model parameter relationship is studied in reference to Zheng Yingren's research results. Thirdly, the result, namely the location of the potential slip surface, safety factor and stress distribution along the potential slip surface, of slip surface finite element method, Bishop method and finite element strength reduction method are compared. It illustrates that the distribution curve shape of shear strength and shear mobilization is quite the same in Bishop Method, but it is not the case for finite element method. For slip surface stress finite element method, the shear mobilization along the slip surface can sometimes oppose the slip direction, which is because the method is based on the actual stress field not the stress field at the critical state. If it happens, the safety factor will be inaccurate. And the shear mobilization is also ambiguous, because it doesn't make the slope move in the slip direction. And what is more, Bishop Method also has such problems, so their results are still quite the same. In this paper, dived segment method is employed to analyze this problem.