Vertical Movement of Pile Groups Caused by Adjacent Large Diameter Shield-Driven Tunneling in Shanghai Soft Clay

Abstract

This study provides a case history of a large diameter shield tunnel (D = 15.43 m) in Shanghai soft clay through field measurement and finite element analysis (FEA). Two elevated bridges - Yixian elevated road and Metro Line 3 which were supported by multiple pile groups - were multi-crossed by a large diameter slurry shield machine. The two bridges were first crossed by the shield machine during the south bound tunneling, and then crossed during the north bound tunneling by the same shield machine. The minimum clearance between the shield skin and piles is 1 m. Field measurement on the movement of the pile groups during the tunneling process, including the vertical, longitudinal transverse, and lateral transverse displacement, was carried out for both bridges. The finite element (FE) software program ABAQUS is used to investigate the movement of the pile groups during the multi-crossing by the slurry shield. A full three dimensional FE model is generated without considering upper structures of the two bridges. Most of the relevant factors in tunneling are taken into consideration in the FE models including the slurry pressure, the grouting pressure, the grouting material hardening and soil- pile interaction. Modified Cam Clay (MCC) model is adopted in simulating the soft clay in Shanghai involved in this tunnel project. The FE results are compared with the field data to provide a better understanding of the disturbance of pile groups caused by the crossing tunneling process.