Performance of a 56 m deep circular excavation supported by diaphragm and cut-off double-wall system in Shanghai soft ground

Abstract

The performance of a 56 m deep circular excavation supported by a double-wall system, consisting of an inner circular diaphragm wall and an outer rectangular cut-off wall, in Shanghai soft ground is studied in this paper. The surveyed data (e.g., lateral wall deflections (δh), horizontal displacement of soil (δs), ground surface settlement (δv), earth pressure (P), pore water pressure (Pw), and stress path) is systematically investigated. The results show that the maximum lateral wall deflections are 0.002% ~ 0.03% of the excavation depth (He). The maximum ground surface settlement (δvm) is generally larger than δhm, which is located at 0.4 ~ 0.6He. Moreover, an innovative formula is proposed to estimate the ground settlement. It is able to distinguish different characteristics of surface settlement in different zones of the settlement profile. The ground surface settlements are mainly induced by surcharge loading and continuous excavation, and they are related to the change in confined water level. The lateral earth and pore water pressures in the active zone are relatively insensitive to the excavation, while the correlation becomes obvious in the passive zone. The findings from this study can be helpful to the design of other similar deep excavations in soft clay.

Performance of Diaphragm Walls during Ultra-Deep Excavations in Karst Areas: Field Monitoring Analysis

“…Figure 9 illustrates the deformation of the representative D-walls during the excavation of the foundation pit in this study. Multiple deformation modes can be observed within the same D-walls during excavation, which differs from the single parabolic deformation mode reported by Wang et al [34] in soft ground. Furthermore, an unexpected deformation mode can be observed, as depicted in Figure 10.…”

“…Figure 7(c) illustrates that the top of the majority of D-walls in Zone 3 exhibited movement away from the foundation pit during excavation, which contradicted the findings of Wang et al [34]. The top horizontal movement of A9 (monitored at point S3), A16 (monitored at point S5), and A211 (monitored at point S72) exhibited rapid increases following the completion of the final level excavation.…”

RETRACTED: A novel back-analysis method for improving predictions of time-dependent ground settlements in deep excavations in soft soils

“…Extensive deep excavation projects are underway to meet the substantial demand for infrastructure construction in these regions such as the Circum-Bohai Sea region, the Yangtze River Delta region, and the Pearl River Delta region (e.g., [2,34,36,51]). The estimation of ground settlement induced by deep excavation is a primary concern for protecting adjacent buildings from potential damage caused by differential settlement (e.g., [1,8,9,15,21,44]). Thus, a reliable calculation method is required to estimate ground settlements induced by deep excavations in soft soils.…”