Chengshi guidao jiaotong yanjiu (Mar 2024)
Stability Analysis of Deep and Large Foundation Pit Construction for Urban Rail Transit Station in Soil Rock Composite Stratum in Coastal Area
Abstract
[Objective] Excavation of foundation pit will cause deformation of surrounding strata and buildings , which affects construction progress and even causes engineering accidents in some degree. In order to ensure the stability and safety of deep large foundation pit in urban rail transit stations, it is necessary to study the stress and deformation characteristics of the soil layer and the enclosure structure during the foundation pit excavation. [Method] With the deep foundation pit excavation for a metro station in Qingdao as the project background and in view of the characteristics of soil rock composite stratum, numerical simulation method is used to analyze the deformation and internal force of the deep foundation pit. Based on the on-site data, the deformation law of ground settlement, retaining pile displacement and supporting axial force during excavation of deep foundation pit under soil rock composite stratum is studied. [Result & Conclusion] The numerical simulation shows that when biaxial high-pressure rotary jet grouting pile is not under construction, the lateral displacement occurs in the east, west and south walls of the end shaft, all towards the internal of the foundation pit, and the maximum lateral displacement of 2.19 mm occurs in the middle of the south wall. During the construction, the deformation of the side wall of the end shaft reaches peak in the process of reinforcement of the rotary jet grouting pile at the end shaft of the foundation pit, and the maximum deformation is 2.21 mm. When the biaxial high-pressure rotary jet grouting pile is not under construction, the peak value of the internal force of the diaphragm wall appears at its waist, and the maximum value is 101 kN. During construction, the internal force of the diaphragm wall structure at the stratum side strengthened by the end shaft jet grouting pile changes obviously, and the peak value of the internal force appears at the waist of the diaphragm wall, and the maximum value is 96 kN. It can be seen that the biaxial high-pressure rotary jet pile has certain effect on reducing the internal force of the diaphragm wall under different construction conditions, but has little effect on the deformation of foundation pit.
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