Abstract
Taking a deep excavation in Suzhou soft soils adopting three support schemes as the background, the excavation performance metrics, including the heave and lateral deformation of diaphragm walls, surface vertical deformation, vertical deformation of surrounding buildings, and earth pressure, are thoroughly investigated based on 15 excavation cases collected in the soft soil area of Suzhou. Based on the analysis of monitoring data, some findings were achieved: the foundation pit deformation is greatly affected by the spatial effect. The existing station can constrain the foundation pit deformation. Benefiting from the combination of various support solutions, the average maximum deflection of the diaphragm wall is 0.10% He. The maximum lateral movement depth of the diaphragm wall (δhm) is mainly located at (He-7, He+12.5). The vertical deformation of the wall top is greatly affected by the excavation exposure time and soil conditions. The heave range of the wall top is (−0.08∼0.26%) He. Under the action of the displacement of the diaphragm wall to outside the pit and the upward displacement of the wall top, the ground surface is uplifted, and the maximum uplift is (0.02∼0.14%) He, ranging from 0.12δhm to 1.13δhm. The maximum surface settlement is (−0.01% ∼ −0.15%) He, ranging from −0.22δhm to −3.11δhm. The form of building heave is mainly affected by the surface heave and the distance from the diaphragm wall (d). When d is within a certain range, there is a heave settlement difference between the adjacent side and the opposite side of the excavation, and the adjacent side undergoes mostly subsidence, while the opposite side undergoes mostly uplift. The peak value of the apparent earth pressure (AEP) envelope is 0.59γHe, which falls within (0.47∼0.78) He. The calculation scheme proposed by Kim can be used to predict the AEP for multiple soil types.
Highlights
With the rapid development of urbanization, the utilization rate of urban space is increasing, and foundation pit engineering often occurs close to high-rise buildings, subway tunnels, municipal pipe networks, etc. (Liu et al, 2012)
At the top and bottom of the diaphragm wall, due to the shrinkage of the top beam and fixed end, their stiffness is relatively high, but there is no prominent constraint in the middle, and the stiffness is low, resulting in an uneven reduction within a certain depth of the lateral displacement of the the statistical results of Liao et al (2015). These results show that this project benefits from the combination of various supporting schemes so that it can better control the lateral displacement of the diaphragm wall in complex environments
Near the upper boundary of the statistical results of Li et al (2019), the deflection range is generally less than at the upper boundary of Analysis of Uplift and Settlement of the Figure 6 shows the spatial distribution of the vertical displacement Vqd of the diaphragm wall under different working conditions and relationship between Vqd and He
Summary
With the rapid development of urbanization, the utilization rate of urban space is increasing, and foundation pit engineering often occurs close to high-rise buildings, subway tunnels, municipal pipe networks, etc. (Liu et al, 2012).
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