Study On The Stability Of Tunnel Group Based On Finite-element Strength Reduction Method

The finite element method based on the strength reduction technique has been increasingly applied to the numerical analysis of slope stability, however, the related researches on tunnel and tunnel group were relatively limited. This article conducted studies on the stability of tunnels based on the strength reduction method, and the main contents are as follows:(1)The current status of tunnel stability is summarized and the strength reduction method is overviewed in the paper.(2)Nonlinear finite element method is very important to study the stability of tunnels, the classification of nonlinear problems is briefly described, and the solution process and iteration convergence criteria of nonlinear finite element method are discussed, nonlinear finite element methods are iterative method, incremental method and Hybrid method.(3) According the analysis on the stability of tunnels using the strength reduction method, three kinds of failure criteria, plastic zone breakthrough criterion, the criterion of abrupt change of the relationship between the displacement(or displacement increment) and the reduction coefficient at a certain characteristic location and the divergence criterion of numerical calculation are analyzed and utilized to discuss the applicability based in different cases of single hole, dual hole and four holes, respectively; in addition, some researches on the tunnel stability in layer of non-homogeneous rock are studied and the applicability of hierarchical reduction and overall reduction is compared.(4) The translated parameters relationship between Drucker-Prager strength criterion and the triple shear unified failure criterion is derived, and the two different strength yield criteria are discussed to analyze the impact to the stability of tunnels, finily, the relationship between influence coefficient of intermediate principal stress and safety coefficient of tunnels is summarized(5) Two different section planes, which are located in separatelyâ…£class and V class rock geological conditions of Dapein river hydroelectric generating station on the China-Burma border, are calculated strength parameters in back-analysis in this paper, and related finite element models are built to analyze the stability of surrounding rock at respective section plane under different operating conditions using the reversed parameters uising the finite-element strength reduction method, these conditions are different order of excavation in phase of construction, operating phase and operating phase under earthquake.