Research on the Law and Prediction of Ground Settlement by Shield Tunneling Construction in Ningbo Rail Transit

Abstract

Ground settlement laws and its control measures attract comprehensive attention in urban rail transit construction, particularly in soft soil area with shield tunneling method. Phase 1 of No.1 rail transit project in Ningbo is constructed by earth pressure balance (EPB) tunneling methods. In this paper, the horizontal ground settlement caused by single tunnel construction is studied by site measurement results. Correlation analysis of tunnel depth, grouting quantity, cover earth thickness, construction parameters and maximum settlement value is conducted. In the end, measurement data are linear fitted by least square method. Compared Peck formula with the result, the parameter selection and its applicability in Ningbo district are discussed. The research shows that the maximum width value of horizontal influence area can be up to 60 meters owing to the soft soil layer. Widths of settlement tank have mostly ranged between 15 and 20 meters. The maximum surface settlement has great linear relationship with grouting quantity, driving speed of shield machine and torque of cutter. But the depth of the tunnel has weak interaction with maximum ground settlement. Abovementioned research findings can provide technical support and theoretical guidance for the following rail transit construction in Ningbo. Keywords-Tunneling construction; rail transit; ground settlements; width of settlement tank; modified peck formula