Abstract: Due to shield tunnel construction disturbance, additional soil stresses can occur and thus soil plastic zones around tunnel may appear around the tunnel. The range of the plastic zone is closely related to grouting parameters, such as grouting pressure and grouting amount. To analyze the disturbance range caused by shield tunneling, the cavity expansion theory is introduced to determine the plastic zone and the disturbance range of the surrounding soil. The effects of backfill grouting pressure and grouting amount on the plastic zone and the range of disturbance by shield tunneling are investigated, and a functional relation between the plastic zone and grouting parameters is derived based on the cavity expansion theory. By defining a disturbance evaluation criterion, a simple numerical method for calculating the plastic zone and the disturbance range during shield construction is proposed based on the finite element method. The results obtained by theoretical formulation and finite element method are compared with the static cone penetration test (CPT) data, showing that the theoretical and numerical results are in a good agreement with those obtained by field tests, demonstrating the validity of the proposed approach. The results provide a theoretical support for the proper choice of grouting parameters in shield construction.

Key words: shield tunnel, grouting parameters, construction disturbance, plastic zone, finite elements