The Reliability Research Of Subway Tunnel By Subset Simulation Method Combining Support Vector Machine

At the beginning of the 21 st century, with the rapid development of China's subway tunnel construction, a great deal of human, financial and material resources have been invested into the construction of the subway tunnel. To construct subway tunnels in urban areas brings a heavy demand of safety. Although the traditional safety factor method can reflect engineering safety to some extent, it can not consider the randomness of variables. On the contrary, reliability analysis method can analyze the uncertainty and randomness of variables, so it has a great significance in the safety evaluation of engineering.This thesis mainly introduces basic principles of several frequently-used analytical methods in reliability, analyzes the advantages and disadvantages of each method in practical application. The subset simulation method, which has some advantages for solving the problem of the small probability of failure, was studied and used to analyze the reliability of subway tunnel, the contents and conclusions of the thesis are including:1. A modified subset simulation method is introduced to improve the insufficient of the traditional subset simulation method and a solution is presented to solve the problem when there are a number of values equaling to threshold value of performance function.2. A reliability analysis method combining the subset simulation method with stochastic finite element method and support vector machine is presented, which takes full advantage of support vector machine, overcome the inaccurate of traditional subset simulation method when the initial sample points is not enough. Comparing with the classical sample, this thesis verifies the accuracy and the feasibility of the new method, so as to be used as a reliability analysis method for subway tunnel.3. Taking Xuzhou Metro Line 3 as an example and modeled by ANSYS, this thesis calculates the failure probability of tunnel lining by the new method and the traditional methods respectively and compares the results. At the same time, the influence of two different variabilities of parameters on calculating the failure probability of tunnel lining is considered: Considering the spatial variability of soil parameters, the failure probability of tunnel lining is quite different when it comes to whether to take the spatial variability of soil parameters into consideration or not. So spatial variability of soil parameters should be considered in the reliability analysis of engineering; Considering the time-dependent change of concrete strength, with time passing by, the tunnel lining's probability of failure will increase as the whole.Finally, from the calculation results, it is easy to see that the probability of failure in such parts as the vault, arch bottom and spandrel is higher, therefore monitoring of these parts should be enhanced.