Time-domain solution for soil feedback induced by shield tunneling in viscoelastic strata considering influences of surcharge loading

At present, the researches on the influences of deformation of surrounding soil induced by shield tunneling in soft soils are generally based on instantaneous excavation conditions, less considering the rheological characteristics of viscoelastic soils. Furthermore, little attention is paid to the impact of surcharge loading on the shield tunneling. From the perspective of viscoelastic foundation, the elliptical convergence deformation mode around tunnel cavity is introduced. Using the complex variable theory and the Laplace transform technique, the time-domain solution for displacement and stress of surrounding soils induced by shield tunneling is proposed under the influences of surcharge loading. Based on the relevant actual projects, the measured values are compared with the simplified analytical solutions, and good consistency is obtained. The results show that the time-domain solution can reflect the influences of shield tunneling on the displacements of surrounding soils under surcharge loading and the development trend of soil deformation with time. Under the influences of surcharge loading, the ground deformation due to tunneling continues to increase as time goes by while the changing rate of soil settlements shows a gradual decline until it reaches zero. The sudden alternation of surcharge loading causes the surface settlement, especially the settlement rate, to change significantly. The research results have certain theoretical guiding significance for tunnel construction controlling within the scope of viscous strata and dense buildings.