Local Refinement Method for Shear Failure Problems of Soil Foundation

In finite element analysis, the mesh coarseness and the type of elements used are vitally important to the accuracy of the final result. Obviously, high accuracy can be achieved by imposing high order elements and dense meshes. However, the computational cost in these cases would be considerable, especially for physically large or three dimensional models. In order to achieve satisfactory results within reasonable computational time, low order elements and local refinement is usually applied. There are two problems to be solved: i) the elements which need refinement are located. This is usually done through various kinds of error estimation. ii) the method for refining without ill composed elements is used. For two dimensional models, local refinement in a mesh consisting of triangular elements is easier than that of quadrilateral element which has better element properties; but using traditional methods for local refinement of quadrilateral elements, is virtually impossible without misshaped elements and/or meshes with ill composed valences occur. In this paper, an alternative low-cost refinement technique for refining both two and three dimensional problems using quadrilateral and hexahedral elements is present. The technique is applicable to linear as well as non linear problems, though in this paper, we focus on implementing the technique in the non linear soil problem of predicting failure mechanisms and collapse loads in soils.