Construction principles for large-sized grid shield tunnelling in soft clay

This paper is based on extensive field measurement from a large-sized grid shield tunnel project. The paper presents the construction principles of shield tunneling in saturated soft clay areas during normal advancement as well as during suspension of tunneling operations. In particular, the paper focuses on the relationship among the most relevant construction parameters, such as frontal face earth pressure of the tunnel, the amount of excavated soil, the advancement speed of tunneling, and the amount and quality of the grouting. These parameters were shown have great influence on the ground surface settlement, which is one of the major concerns when a tunnel is advanced under populated urban areas. In addition, the paper presents issues related to mechanical models of continuous ground surface settlement and the rheological phenomenon and the deformation mechanisms during suspension of tunneling.