Abstract:Deep excavation projects in soft soil regions are prone to safety risks such as supporting structure instability and excessive deformation due to the high compressibility, low strength and significant rheological properties of soil. Based on accident statistics (2020—2024) from the Ministry of Housing and Urban-Rural Development (MOHURD), the soft soil excavation accidents accounted for 78% of cases. Combined with an excavation case of a WWTP, the deformation mechanisms of deep excavations in soft soils and the technical limitations of traditional support systems are systematically analyzed. The research shows that the strength attenuation of cement soil and the percolation-creep interaction in the coupling effect of soft soil creep and support structure are the main causes of deformation. The disturbances such as over-excavation during construction and over-limit dynamic loads, as well as parameter deviations like insufficient design depth of soil penetration, will further intensify the risks. Taking the SMW method piles as an example, the creep failure mechanism is elucidated, and a collaborative optimized path of “material - design - construction” is proposed, including the measures like low water-cement ratio cement soil modification to form a closed-loop control methodology of “warning - analysis / decision - execution”. Through empirical analysis of two typical excavation deformation accidents, the efficacy of emergency measures such as unloading counter-pressure and support reinforcement is confirmed that the subsequent deformation rates are successfully reduced to manageable levels, which provides the mechanism analysis, control remediation and preventive measures for survey, design and construction of deep excavation projects in soft soil regions, and has the significant socio-economic benefits and promotional values.
