Abstract
Considering the deep foundation pit of a car dumper room close to the Beijing–Baotou railway, the countermeasures of the foundation pit design are analyzed according to the surrounding environment and stratum conditions. Through Midas GTS software as well as field measured results, the construction effect on the adjacent railway subgrade is discussed. Therefore, the deformation characteristics of the foundation pit as well as the retaining structure, including the railway subgrade, caused by the excavation process, are revealed. The results show that the five-sided water-stop structure formed by cement piles around and at the bottom of the pit avoids the consolidation settlement of the adjacent railway subgrade caused by deep dewatering and also reduces the lateral displacement (i.e., in a horizontal direction) and the heave of the pit bottom. As a result, the lateral displacement near the railway side is larger than that of the retaining structure on the other side due to the subgrade on the pit side. The cross-lot bracing across the foundation pit will transfer the bias pressure of the subgrade to the retaining structure far away from the railway, while the transfer effect of the knee bracing is not obvious. The deformation of the railway subgrade and its evolution rate caused by the removal of internal bracing is significantly greater than the subgrade deformation and the change rate of deformation caused by excavation. The research results provide useful guidance for the deep foundation pit design.
Highlights
With the increased development of urbanization construction, there are increasing foundation pit projects near the existing structures in recent years (Seong et al, 2011; Zhang et al, 2018; Li et al, 2020)
To strictly restrict the deformation and settlement of the adjacent railway, it is of importance to control the change of groundwater due to the excavation of the foundation pit, as well as the deformation values of the retaining structure
For deep foundation pit with settlement-sensitive structures, such as railway subgrade close to the foundation pit, the groundwater control scheme with a five-sided water-stop structure and appropriate pressure relief wells in the pit, it can effectively avoid the impact of great depth dewatering on the settlement of adjacent subgrades and determine the deformation properties of the retaining structure and reduce the heave of the bottom of the pit
Summary
With the increased development of urbanization construction, there are increasing foundation pit projects near the existing structures in recent years (Seong et al, 2011; Zhang et al, 2018; Li et al, 2020). Once the deformation of buildings adjacent to the foundation pit exceeds the limit value, differential settlement occurs. Distortion deformation occurs, resulting in the destruction of the buildings close to the deep. The existing railway subgrade and dynamic load on the stratum near the foundation pit result in an asymmetric load on the retaining structure on both sides, leading to an obvious increase in the applied stresses and corresponding deformation and settlement of the retaining structure (Ying et al, 2011)
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