A Study On Slope Stability Of The Foundation Trench Of Immersed Tube Tunnel

Tunnels are good solutions to transportation problems in large cities separated by large rivers. Immersed Tube Tunnel (ITT) is a principal choice because of its unique advantage in the currently existing construction way.This paper discusses the immersed tube tunnel underwater slope foundation trench slope reasonable rates, this problems directly affect the underwater excavation of earthwork project and after the sinking pipe backfill earthwork, directly affect the duration and cost. Slope with slow slope rate, Foundation trench excavation of earth and backfilling of earth are both relatively larger and the project is not economic; slope with steep slope rate, then the construction may lead to slope collapse will bring huge economic losses. Therefore, a study on Immersed tube tunnel underwater slope of reasonable foundation trench slope of the rate has very great significance.Analysis of the underwater slope of the computing model to compare the analytical calculation and numerical results, based on the foundation trench flow field, analysis of underwater slope stability with hydrostatic conditions and analysis of underwater slope stability with hydrodynamic conditions draw a reasonable foundation trench slope rate. Analysis of the distribution of foundation trench flow is obtained at the lower river flow and lower speed of sinking tube sections, the flow field in the hydrostatic pressure distribution and pressure distribution in little difference; assume that at the higher river flow and lower speed of sinking tube sections, the downslope seepage flow emerges,consider the most adverse situations. Analyzes the underwater slope calculation model based on the above analysis and compare the results of analytical calculation and the numerical results. In the numerical calculation mainly use the strength reduction theory, there are three failure criteria in slope stability analysis:(1) the non-convergence of the numerical calculation;(2) the abruptness of the displacement or deformation at a certain characteristic location;(3) the connectivity of plastic zone on slip surface. As a key of finite element method based on shear strength reduction, the slope failure criterion will affect the accuracy of the calculation. To analysis the above several instability criterion and compare the result. The conclusion is that use non-convergence method to calculate safety factor of anti-slide Pile support slope is feasible.Through this analysis, combined with the actual situation, come to the slope ratio of foundation trench of the Zhoutouzui ITT:the slope ratio of highly weathered sandstone layer is 1:1, the slope ratio of sub-clay layer is 1:2, and the slope ratio of sand layer is 1:3.There are 57 illustrations,25 tables and 46 references.