Study On Failure And Reliability Of Tunnel Structure

Traditional method of safety coefficient is used widely in the analysis of underground construction engineering. Because stochastic characteristics of all factors and variables can not be considered with this method, many shortcomings of the method can not be solved by itself. The characteristic of structural reliability is described by structural reliability, which makes the structure design more scientific, reasonable than traditional method, and it can further reflect the essence of the question studied.Based on a lot of documents, the paper discusses the factors which affect the failure of the tunnel and the failure forms by analyzing the causes of the failure of the tunnel,systematically elaborates the judgement criterion for the tunnel failure,and defines the allowable limit displacement as the criterion.Focused on the practical situation of the Qinling No I tunnel project, the analysis of 3-D nonlinear finite element of the typical placement block is given with Druker-Prager Criterion under utilizing its actual data. The results show that there is concentration of stress at hance of the tunnel,the maximum of the stress is at the point of 1/3 distance from the arch foot ,and the stress at the vault is the minimum.After the excavation and supporting,the displacement of the vault is the largest,the displacement of the hance is intermediate and the displacement of the arch foot is the smallest.The results are line with the practical data.At present the reliability analysis of large-sized cavern structure has become the concern of many scholars. Because of the complexity of underground cavern structure, the performance function can not be expressed by definite equations. The first-order second-moment method and its concerned methods can not be applied. Monte-Corla method needs thousands of simulation, whose practicability is doubted. The function is made by response surface method in the paper,and combines the response surface method with the Monte—Carlo method to carry out the reliability analysis for the Qinling tunnel .The result shows this tunnel is in the stability status.The value of the reliability index β is the largest at the arch foot,at the hance is the intermediate,and at the point of 1/3 top of the hance—it varies from small to big then to small,finally becomes the smallest at the vault.The result agrees with...