Time-dependent surrounding soil pressure and mechanical response of tunnel lining induced by surrounding soil viscosity

A numerical simulation method of shield tunnel excavation is developed to capture the time-dependent deformation behaviour of surrounding soil. The simulation method consists of four parts: (i) an elastic-plastic-viscous constitutive model that can not only reasonably describe the viscous deformation behaviour of soil, but also appropriately calculate the plastic deformation under typical stress paths of excavation; (ii) simulation of main factors related to shield tunnel excavation, including the shield machine, face pressure, lining, grout behavior, and contacts between multiple media; (iii) a simulation procedure for excavation to reflect the process of shield tunnel excavation and achieve reasonable stress and strain fields at the end of the construction stage; (iv) a creep process that is used to investigate the long-term mechanical behaviours of the surrounding soil and tunnel lining. Taking the CK570H tunnel project in Taipei as the background, a numerical simulation is conducted by adopting the developed simulation method. Based on the simulation results, the radial and circumferential stresses acting on the lining, which are induced by the surrounding soil viscosity, are analysed. The rule of the mechanical response of lining, including its deformation, bending moment, and axial force, with time is revealed. On this basis, the long-term safety of the lining is evaluated.