Advance speed-based parametric study of greenfield deformation induced by EPBM tunneling in soft ground

For earth pressure balance machines advancing through soft ground, it is essential to control the mechanical driving parameters, such as skin friction, face pressure and cutter torque, to minimize the influence on the surrounding environment. A test at a greenfield site was conducted to determine the tunneling-induced soil deformation and the relationship between the mechanical driving parameters and advance speed. A method based on fuzzy statistics was proposed to calculate the standard values and deviations of the advance speed and mechanical driving parameters at the normal state of advancement. A finite element model verified by field measurements was employed to investigate the greenfield response and the effect of the mechanical driving parameters on soil deformation. Further, the response of soil deformation to the mechanical driving parameters was analyzed at the normal state of advancement. The results showed that at the normal state of deep advancement, the skin friction deviation had the greatest influence on the displacement of both the surface and subsurface. Increasing the skin friction increased the settlement above the tunnel and reduced the heave beneath the tunnel. The higher face pressure resulted in smaller settlement near the tunnel crown and heave near the tunnel invert. The larger cutter torque was only able to increase settlement near the tunnel crown. The combined effect of the mechanical driving parameter deviations was dominated by skin friction for the surface settlement. Regarding the subsurface vertical displacement near the tunnel, an offsetting or superimposed effect occurred at various advance stages. The mechanical driving parameter deviations based on a higher advance speed reduced the vertical displacement above the tunnel.