Abstract:Against the backdrop of rapid urban development, the higher requirements are proposed for the safety and construction efficiency in the construction of deep foundation pits adjacent to subways and underground pipelines. Addressing the challenges of deep excavation construction in complex soft soil conditions, and combined with the practice of a large-scale integrated development project in Shanghai, a rapid sub-pit construction technology system is adopted, which combines “four-axis mixing pile water-stop curtain + ultra-thick bottom plate jumping bin method + annular bottom plate advance sealing + concrete support axial force servo system”. The water-stop efficiency is improved through four-axis mixing piles. The jumping bin method is used to decrease the setup of post-pouring belt and the cracks are controlled. The circular bottom plate is formed into a closed structure in advance to optimize the critical route schedule. And the axial force servo system is utilized to actively regulate the support deformation. The implementation results show that the maximum lateral displacement of deep foundation pit soil is controlled at 33.7 mm (2.56‰He), the impacts on the adjacent metro structures are effectively reduced, the exposure risks brought about by work stoppage during the Spring Festival are successfully circumvented, and the construction safety and organization efficiency are significantly enhanced. The technical system has achieved the dual objectives of deformation control and schedule compression, providing a viable pathway for rapid construction of deep foundation pits in similarly sensitive environments.
