Study On Consolidation Behavior Of Soil Around Shield Tunnel In Viscoelastic Foundation

The subway is still the key of the development of urban rail transit at present and for a long time in the future.On-site monitoring of the built subway shield tunnels shows that the long-term settlement of the subway shield tunnels in soft soil areas is very large,settlement development lasts a very long time,and there is great unevenness along the longitudinal direction of the tunnel.While shield construction disturbs the soil,it also introduces new seepage boundary conditions,which redistribute the stress field and seepage field,reconsolidate the soil,and rheological deformation.That’s the main cause for the long-term settlement of the subway tunnel.Starting from analytical theory and numerical analysis,this paper uses existing engineering measurement data combined with analytical theory and numerical analysis to conduct an in-depth study on the consolidation behavior of the surrounding soil of a shield tunnel in a viscoelastic foundation.The main innovations are as follows:1.Introduce the generalized Voigt rheological model to simulate the time relationship of viscoelastic foundation soil stress-strain,combined with the TerzaghiRendulic consolidation theory and the free strain and continuity conditions of the soil to establish the consolidation governing equation.2.Considering the boundary conditions of the shield tunnel under the three cases of complete leakage,no leakage and partial leakage,the analytical solutions of excess pore water pressure in the soil around tunnels with different leakage degrees in viscoelastic foundation are derived by using the complex variable function method.The dissipating law of excess pore water pressure and the development law of consolidation degree in soil surrounding the tunnel are studied.The influence of soil permeability coefficient,soil rheological parameters and tunnel leakage degree on soil consolidation behavior around the tunnel is also researched in this paper.3.Use the universal finite element software ABAQUS to establish a numerical model of a shield tunnel in a viscoelastic foundation.The numerical analysis method and the analytical method in this paper are used to solve the same problem,and the calculation results are compared and analyzed.Based on the above data,combined with the Shanghai Metro Line 2 shield tunnel engineering example,in-depth study has been conducted on the dissipation of excess pore water pressure of the soil around the tunnel and the development of long-term settlement.