Numerical Simulation Of The Shield Tunneling In Soft Soil Stratums

With the continuous, speed, healthy, stable development of our national economy, the construction of subway in economy prosperous cities along the coast becomes the important solution to the serious problem of city public transportation. The geological condition of cities along the coast is the soft soil straturns, so the research of the problem of shield tunneling in the soft soil stratums is very practical. Based on these, the following items are studied:Firstly, the research background and the shield tunnel are introduced; the research present state about the effect of the shield tunneling on surroundings is summarized; some shortcomings in the current researches are pointed and the works in the article are presented.Secondly, bow to simulate the shield tunneling in the 2D plane strain condition is explained including how to simulate the soil loss, the choice of element, the discretization of the finite mesh, the set of calculation domain and boundary conditions, the choice of the material parameters and the division of the calculation step.Thirdly, the front modeling method is used to analyze Shanghai No.2 Subway Line. In calculation the linear elastic model, idealized elastic-plastic Drucker-Prager model, hardened elastic-plastic modified Cambridge model are used. Then the calculations from the three constitution models are analyzed and compared to the measured data, so that the constitutive model more suitable to model the shield tunneling can be decided.At last, based on the front modeling method and the chosen constitutive model the shield tunnel in soft soil is systematically calculated to study the relationship between the surface swelling and many influencing factors, such as the burial depth of tunnel, the dimension of tunnel, the rate of soil loss, the mechanical parameters of soil, the overconsolidation ratio and the coefficient of the static earth pressure. The liner resistance has also been studied. The relationship can be employed to direct the design and construction.