Parametric Finite Element Analysis Of Composite Ground

With the fast development and wide application of the composite ground technique, the theoretic study on the composite ground has greatly lagged behind the engineering practice. Several scholars have studied the working mechanism of the composite ground by means of the analytical and numeric method. The parametric variational principle is used to study some problems on composite ground and some instructive conclusions have been drawn. In this thesis, the parametric finite element quadratic programming method is adopted to analyze the displacement and stress field of the soil in the composite ground. Firstly, the concept and classification of the composite ground are briefly introduced in this thesis. The current research status of composite ground is summarized up, especially the research progress in the numeric analysis. The minimum potential energy principle of the elasto-plastic problem, the parametric variational principle and the solving procedure of boundary value problem are introduced. The advantages of parametric variational principle relative to classic variational principle are expounded, at the same time the limitation of parametric variational principle is discussed when it is used to solve complex problems. Secondly, the routine finite element methods of elasto-plastic problem such as iteration method and incremental method are also introduced. The element analysis method and the construction and assembling method of stiffness matrix, plastic energy matrix, reinforcement matrix, and restraint matrix are emphatically introduced. The linear complementary algorithm of standard quadratic programming is introduced. The parametric quadratic programming algorithm of free design variables and its programming method are also discussed in detail. Finally, axisymmetrical strain analysis program is work out using FORTRAN90 according to parametric finite element quadratic programming method and some key points about the program are explained. With the help of the program, the displacement field and stress field of soil in the lime pile composite ground are analyzed on the assumption that the soil obeys Tresca or Drucker-Prager yield criterion. The computation results are in accordance with the analytical solutions or the results from the software ANSYS. This method is proved to be effective and feasible. The displacement field and stress field of soil in the lime pile composite ground are calculated by parametric finite element quadratic programming method in this thesis. The application range of parametric variational principle is enlarged in the numerical analysis of composite ground.