Improvement Of Numerical Manifold Method And Discussing About Contact Parameters

Rock mass is a kind of discontinuous material with cracks and joints. So it is not adaptable to calculate with FEM (Finite Element Method) as a kind of continuous material, or to calculate with DEM (Discrete Element Method) or DDA (Discontinuous Deformation Analyses) purely as a kind of discrete material. Now calculating both continuous and discontinuous mechanics with computer becomes a hot question and a lot of new methods are made to solve this question. NMM (Numerical Manifold Method) that can union the FEM and DDA to a system to simulate the mechanical activities of continuous and discontinuous materials has been developed quickly. But a important question in NMM is still not solved that the Spring Parameters which is used to control the opening and closing of fractions or joints can't be selected properly and can only get a range which of cause is not suitable to all conditions. For solving this question, a lot of numerical methods are studied in this thesis and their traits are summarized and compared and the defaults are pointed out. Then the traits of the method NMM used to solve this question are analyzed and Desai Element used in FEM is introduced to NMM, a formula is set up in which the stiffness of spring is selected according to the cut_in depth. Then the parameter of spring is properly selected; and the peculiarity of triangle element when contact is analyzed and a program is made to get contact information automatically.The program in this thesis is programmed on the base of NMM2001, which is programmed by Prof. Wang Zhiyin and two order global displacement function formed by one order displacement cover function and one order weight function is adopted in the program. The high order simplex integral function is calculated with Matlab and then the program was made to calculate by time steps and force can be executed to step by step. The formula of initial stress field is modified according to displacement cover function.Finally, some examples are given in this paper. The results have shown that the improvement is suitable. The defects of NMM are analyzed and the development expected.