Application Of Fe Strength Reduction Method In Tunnel Stability Analysis

With the rapid development of science and technology,lots of tunnel and underground engineering come out in areas such as railways. highways. subways and urban construction. thus higher requirements are needed in the stability analysis of such areas . Method of FE strength reduction has been successfully applied in slope(slide)analysis,the paper is about the application study of FE strength reduction method in the stability analysis of tunnel and underground engineering. contents are as follows:①currently,there is no concept of quantitative safety coefficient in tunnel engineering. Based on the concept of strength reduction,the rock whose strength parameters have been reduced is dealt with in the state of limited failure.,then coefficient of reduced strength is the safety coefficient.②Study on the failure mechanism of tunnel,based on FE strength reduction method. indicates that the tunnel is destroyed from plastic area of arch foot and spandrel,on which stress concentration is clear. Plastic area develops upwards in arch foot while downwards in spandrel. both of which are concatenated in inner rock. Non-converged calculation shows that the tunnel is destroyed. According to the features of displacement and plastic strain in ruptured area. max of equivalent plastic strain in each section of numerical simulation contours are connected to lines. which is the potential position to be destroyed.③Variation of safety coefficient corresponding to types of rock parameters in current norms is calculated and analyzed based on the concept of strength reduction,which is of great significance to tunnel construction.④Rock and lining safety coefficient are involved in tunnel design,and as to Composite lining .safety degree of rock and lining must be insured. Rock safety coefficient is calculated by means of FE strength reduction. while lining safety coefficient is figured out with the traditional structure method.⑤Take cuntan tunnel with small spacing of chongqing as an example .the safety factor of surrounding rock and lining is calculated. the results betterly reflect the stability changes and security reserve situation of surrounding rock and the lining during the construction.and can be used as basis for stability evaluation.