A Fuzzy Theory-Based Study On The Influence Of Driving Parameters To The Surrounding Soil Deformation In Shield Tunneling

In recent decades, earth pressure balanced machine tunnel boring technology has been increasingly applied to soft ground. Disturbing the surrounding strata, however, inevitably results in ground deformation and surrounding soil movement. Once the movement is too large, it would endanger the safety of the adjacent buildings and pipelines. 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, including the skin friction, face pressure and cutter torque, 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. Within a certain range of rings having parameter deviation, it produced a linear growth-influence on the surface deformation with the increasing number of the deviation rings.Futher, fault tree basic events were derived from the mechanical driving parameters during tunneling. Considering the calculated results in the parametric study and the field data in EPBM, the quantitative risk analysis on the risk loss and failure probability was performed. The results showed that the risk factors were ordered based on the risk to the ground settlement at the normal state of advancement. Therefore, the ground settlement induced by shield tunneling can be fine controlled according to the order of the risk factors.