Research On FEA And Its Application To Soil Engineering

In soil engineering, there are some traditional problems such as stress-strain and consolidation-settlement to be studied. Because of their complexity, only a few problems can get accurate solutions. With the development of computer and numerical modeling techniques, many numerical methods have been established and applied to this field. FEM (Finite Element Method) is one of the most effectives. The application of FEM to soil engineering is studied in this thesis. The main contents are listed as follows:(1) Some widely used numerical methods are summarized. The principles of FEM and the ways of analysis are dissertated in detail. The elements adopted in this study are analyzed and the practical expressions are formulated completely.(2) Some famous constitutive models are introduced. The advantages and disadvantages of these models and their applicable conditions are described generally. Especially, several constitutive models adopted here are also expatiated thoroughly. The nonlinear analysis of soil structure is discussed.(3) The governing equations based on Biot theory are fully expatiated. The method of 8-node iso-parametric element coupled with 4-node iso-parametric element is deduced. And then, 6-node constant thickness contact interface element coupled with 4-node iso-parametric element is developed to simulate the smear layer of drain wells. The new kind of element has made a better simulation of PVD/sand drains-improved ground with surcharge preloading.(4) The error estimation of adaptive time-step in consolidation are studied. Compared with the traditional methods, which usually give limitations to the time step, a better precision and less computation quantity can be obtained.(5) According to the theories and methods mentioned above, the program RIFEM is developed. The basic structure and the main functions of this program are introduced briefly. Some key techniques in programming are also presented. The program has been verified by some examples.(6) Two practical projects are taken as the examples by this program. The results are quite good and can be used in the design and the construction of soil engineering.