Abstract:With the increasingly intensive development of urban underground space in China, the construction adjacent to operational shield tunnels has become a common challenge. As flexible structures, the shield tunnels are particularly susceptible to disturbance from adjacent construction activities in soft soil areas, necessitating stringent deformation control requirements. Aiming at the common protection measures for construction above shield tunnels, the applicability and limitations of the zero-loading method, isolation method, portal frame transfer method and rapid excavation-backfill method are analyzed. It is pointed out that in actual engineering, there are key problems such as the difficulty in achieving zero loading, the uncertainty of geological disturbances, the complexity of relative positional relationships, and the difficulty in controlling the construction process. Combined with an engineering case in a coastal soft soil area in Shanghai, the theoretical analysis and practical verification are conducted for two working conditions of trenching unloading and road loading above an operational shield tunnel. The engineering practice demonstrates that the theoretical analysis needs to be further conducted in combination with the actual situation of the project; otherwise, the inaccurate conclusions may still be drawn. Additionally, it is necessary to enhance the automated monitoring and information-based construction during the construction period so as to adjust the response measures in a timely manner. The research findings can provide a reference for micro-disturbance control projects of shield tunnels in similar soft soil areas.
