In response to the problem of deformation caused by surrounding construction disturbances in existing shield tunnels in soft soil areas, lateral horizontal grouting is often used. Based on an independently designed and developed lateral grouting experimental device, the mechanism of horizontal lateral grouting on the convergence deformation of the tunnel was determined. A three-dimensional finite-element analysis model was established to study the force and deformation characteristics of the tunnel tube sheet, and to verify the correctness of the model test results. The grouting remediation efficiency, eta, was introduced to establish the relationship between the grouting volume and the convergent deformation. The results show that the tunnel tube sheet was subjected to asymmetric additional soil pressure along the ring direction, and asymmetric displacement occurred, which was most obvious on the grouting side. The additional moment distribution was symmetrical and spindle-shaped, and the peak bending moments mostly appeared in the arch roof, the arch bottom, and the arch whist. With a continuous increase in grouting volume, the efficiency of the grouting remediation decreased, and the two were negatively correlated.

Shield tunnels built in soft soil are prone to settlement, which is often accompanied by convergence deformation, further resulting in a series of damages to the tunnel structure and compromise its safety in service. This paper presents an engineering case on the settlement development and internal drilling grouting remediation of a tunnel in Shaoxing Metro Line 1, where the inner diameter and thickness of the tunnel linings are increased to be 5.9 m and 400 mm simultaneously. The tunnel settlement arises from a comprehensive analysis of several contributing factors, encompassing ground disturbances such as pile driving, pile extraction, backfilling of pile holes, road structure construction, and road traffic. A grouting remediation plan is thoughtfully designed, including a careful assessment on the necessity for a temporary steel support system which is based on a full-scale three-ring test of the tunnel structure. The deformation of the tunnel during settlement and grouting processes is thoroughly analyzed to investigate the deformation resistance capacity exhibited by the thickened larger-diameter tunnel. The case study and experimental results demonstrate that tunnel structures with an increased diameter and thickness have better deformation resistance than conventional metro tunnels in soft soil layers. The analysis of this study can provide a reference for tunnel structures optimization and similar grouting remediation projects in shield tunnels.