Analytical prediction of tunneling-induced ground movements and liner deformation in saturated soils considering influences of shield air pressure

Abstract

Complex underground constructions in urban areas require strict predictions for ground movements and liner deformation induced by shield-driven tunneling, in which the complex interaction mechanics between ground and liner play a substantial role. Previous studies, however, provided little information on the ground-liner interaction and less attention to the effects of groundwater and compressed air during the shield operation. This paper presents a closed-form analytical solution for predicting long- and short-term ground deformation and liner internal forces induced by tunneling in saturated soils in which shield excavation effects with and without air pressure are both considered. The oval-shaped convergence deformation pattern is incorporated as the boundary condition of displacements around the tunnel section. This paper also investigates the difference between uniform radial and oval-shaped convergence deformation patterns on the ground and tunnel responses. Generally, the predicted ground movements by the oval-shaped deformation pattern aligns well with measured data of actual tunnels with and without considering the shield air pressure. It is comparatively observed that the shield excavation under air pressure obtains larger ground deformation than the non-pressure condition, and the long-term ground settlements induced by tunneling in saturated soils are confidently larger than the short-term. Moreover, the effects of sensitive parameters, including the shield air pressure, the long- and short-term effects on the tunneling-induced ground movements are assessed based on the oval-shaped deformation pattern. Furthermore, parametric analyses are conducted to measure the influences of concerned tunneling coefficients on the liner displacements and internal forces, namely, soil Young's modulus, soil unit weight, coefficient of lateral soil pressure, tunnel radius, tunnel buried depth and gap parameter. In summary, the analytical approach proposed in this research provides an effective insight into the ground-liner interaction mechanics related with the shield air pressure, which can serve as an alternative approach in the preliminary design for conservatively estimating the excavation influences caused by tunneling in saturated soils.