Elastoplastic Boundary Element Method And Its Application To Underground Engineering

Because of the rapid growth of the world population, the human living conditions are having been changed constantly; the shortage of resource and the desertification of land are becoming serious problems. As to this, some countries consider that the excavation and application of underground tunnel is important in existence and development of mankind except adopting comprehensive treatment. With the sustainable development of the economy of our country, we have made a breakthrough in excavation of underground tunnel and its usage. The field used in underground tunnel is becoming more and more extensive and its scale is becoming larger and larger. So, it has theoretical value and project significance to study on tunnel excavating, especially the distribution of stress and displacement of tunnel.There are two main methods to solve engineering problems. One is theoretical method, the other one is numerical method. However, it is limited to solve problems with theoretical method. Because of applying and popularizing of computer, all kinds of numerical methods play an important part role in solving engineering problems. Numerical method is mainly component of finite different method, finite element method and boundary integral equation method (BEM in short). Compared to the other numerical methods, BEM has its own predominance, which are listed as follows: firstly, BEM debases the dimensions of problems; secondly, it only discretizes elements on boundary of object and it is very simple to solve infinite or half infinite problems; thirdly, when solving singularity problems, it's simple to calculate, because of not needing element discretized within the domain of object; last but not the least, BEM needs lesser man-made data, which can reduce the possibility of errors.This paper will adopt boundary element method, calculate and analyze the distribution of stress state and displacement and the changes of law. On the basis of summarizing predecessors' fruitful results, we work out the boundary element method program of linear elasticity for an infinite region in three dimensions. First of all, comparing the numerical stress state and displacement of a circle underground tunnel in deep depth with the theoretical stress and displacement distribution under plane strain state, we check that the program is accurate and efficient. Then we utilize the procedure to calculate and analyze the stress and displacement distribution, to analyze the stress concentration on tunnel section, and to analyze the changing law of stress and displacement along tunnel's axis of one single underground tunnel, two parallel underground tunnels, and two perpendicular tunnels. Then, we give the stability of rock body on tunnel section. At last, we learn and deduce boundary element method in elasto-plastic problems, provide a simple example, and carry on preliminary study on boundary element method in elasto-plastic issue, all of which are basic for further study. The results of this paper can do qualitative guidance to the project.