DOI: 10.11648/j.ajce.20261404.15 ISSN: 2330-8737

Application of Deformation Control Technology for Deep Foundation Pits Adjacent to Subways in Soft Soil Areas

Jingde Liu
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Unloading caused by the excavation of foundation pit will lead to the deformation of the surrounding strata and the adjacent metro structures. Excessive structural deformation will threaten the normal metro operation and even the safety of the subway, so effective deformation control measures are indispensable. This study takes a deep excavation project neighboring two operating metro lines in Shanghai as an example and the deformation control techniques of foundation pit excavation are introduced. Overall, the plane division excavation is adopted to reduce the exposed length and the time-space effect of the foundation pit. In order to effectively control the deformation of the enclosure structure adjacent to the subway, the high-stiffness diaphragm walls are utilized as the retaining structure along the metro sides and the concrete axial force servo system is adopted for the second strut to achieve active deformation control. Meanwhile, triaxial cement-soil mixing pile reinforcement is arranged inside the pit to enhance the resistance of the passive soil zone. Furthermore, some of the diaphragm walls deepen as penetrating curtain to control the adverse environmental impacts of dewatering of micro-confined aquifer. The deformation of diaphragm walls and the metro structures is monitored and analyzed. The result shows that the maximum displacements of the diaphragm walls and the metro structures are 15.7mm and 4.8mm, respectively, both complying with the relevant deformation control standards and verifying the effectiveness of the proposed deformation control methods.

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