Field measurement analysis of the influence of double shield tunnel construction on reinforced bridge

Constructing subway systems by shield tunneling in urban area may require tunnels to cross through pile foundations of buildings and bridges, which will definitely affect existing structures. Therefore, it is of great importance to study the construction schemes and influence of shield tunneling on reinforcing and rebuilding bridges. Investigating the case of the double-line shield tunnel of Hangzhou Metro Line 2 crossing through Fengqi Bridge, this paper discusses the project of reinforcing Fengqi Bridge and analyses monitoring data before and after the shield body crosses the bridge. Modification of Fengqi Bridge involves expansion and reinforcement of the raft foundation and improvement of composite ground. Our research findings indicate that these enhancements can effectively decrease bridge settlement during tunneling and improve mechanical conditions of bridge structures. Meanwhile, shield tunnel construction cuts pile and causes pile foundation displacement, leading to settlements behind bridge abutment, deck surface, and pipelines. Settlement of pipelines even exceeds the allowable levels. In addition, due to differences in settling mechanism between pile foundation and soil, differential settlement occurs in both sides of the bridge head and consequently bridge bump arises.