study on long-span and variable-section foundation pit excavation in muddy silty clay

The construction of large-span and variable-section foundation pits in silty soil is challenging. soil creep often leads to engineering problems such as excessive settlement, uneven settlement, and slope instability. this study proposes a new construction method, which is suitable for the inconsistent bottom elevation of a foundation pit by taking the long-span and variable-section foundation pit in nanjing as an example. the construction process parameters were determined based on abaqus, and the accuracy of the numerical model and safety of the construction method were verified by field monitoring. the results show that foundation pit deformation increases with the distance between the supporting erection and the step length. basal uplift decreased with an increase in excavation distance in the shallow area. the influence of the steel support erection time within 12 h on the foundation pit deformation was the most evident. the proportion of creep deformation in the foundation pit deformation on the early excavation side was approximately 21.6%, which was higher than that on the late excavation side. the location of the soft soil layer has an evident influence on the deformation of the foundation pit, and the creep deformation can reach 11% of the total displacement when it is located at half of the excavation depth. © the author(s), under exclusive licence to the iran university of science and technology 2023.