Study On Construction Effects Of Shield Tunnel Excavation To Adjacent Bridges Based On HSS Model And Control Measures

There are more and more projects of urban subway tunnel passing through adjacent bridges.If the construction is not proper,it will cause the uneven settlement and affect the safety of the bridge.Shield method is widely applied in tunnel construction because of its advantages of safety,efficiency and no influence on ground transportation.At present,there are few researches on shield tunnel construction process and construction parameters.The M-C model is mostly used to simulate it.But there is a great error in the prediction of the displacement field.HSS model including HS model parameters and small strain parameters is suitable for numerical analysis of tunnel excavations.Because HSS model can not only reflect shear and compression hardening but also account for shear modulus attenuating with strain in tiny strain range.In this paper,a HSS model with geotechnical test parameters is adopted in the background of a subway shield tunnel in Jinan.It focuses on the evolution mechanism of the displacement field and the process response of the bridges during the construction of the tunnel from the aspect of the earth pressure,grouting pressure and the thrust force.The control measures of construction process are proposed,which could be used to give some reference to similar shield crossing projects in the future.This article mainly carried out the following works:?1?On the basis of literature collection,the paper emphatically analyzes the construction characteristics of metro shield tunnel and the influence of main construction parameters on the surrounding environment.The application of all constitutive models in tunnel construction analysis shows that the prediction results of HSS model are closer to the measured values.And it has better applicability in numerical simulation of tunnel construction.?2?According to the experiment scheme determined by geotechnical test method standard and related literature,the strength parameters?c',?'?and stiffness parameters(E₅₀^{re f},E_ur^{re f},E_oed^ref)of HSS model are measured.The values of eight parameters,such as,?,m,?_{u r},p^ref,R_f,K₀,G₀^{re f},?_0.7,are obtained with empirical formula.?3?The finite element analysis method is used to simulate the initial construction plan of R1 shield tunnel.It is found that the scheme has great disturbance to the strata,and the bridge settlement exceeds the control standard.?4?On the basis of initial construction plan,isolated piles are applied for bridge protection.It focuses on the evolution mechanism of the displacement field and the process response of the bridges during the construction of the tunnel from the aspect of the earth pressure,grouting pressure and the thrust force.?5?The reliability of HSS model in tunnel construction simulation is verified by comparing the numerical simulation results with the measured data.?6?Combined with literature and simulation results,the earth pressure,grouting pressure and the thrust force are optimized when Jinan rail transit passes through typical silty clay formation.And the control measures and suggestions are put forward.