Deformation Law of the Diaphragm Wall during Deep Foundation Pit Construction on Lake and Sea Soft Soil in the Yangtze River Delta

Abstract

So far, there have been a large number of diaphragm walls in the Yangtze River Delta as engineering examples of deep foundation pit maintenance structures in subway stations, but there is a lack of systematic research and summary on the deformation characteristics of ground connecting walls. This study aimed to clarify the deformation law of the diaphragm wall during the excavation of a deep foundation pit in a soft soil region. Based on the monitoring data of the diaphragm wall of the deep foundation pit of the Hangzhou metro station, the monitoring data of the deep foundation pits of 15 subway stations in Shanghai and Ningbo cities around Hangzhou were considered. Grouping and classification methods were used to analyze the similarities and differences in the deformation characteristics of the diaphragm wall in the three regions. The results indicate the following: the maximum lateral deformation of the diaphragm wall in Hangzhou increases linearly with the relative depth of the maximum lateral deformation. The maximum lateral deformation of the foundation pit in Hangzhou is 0.072% H∼0.459% H, with a mean of 0.173% H. The wall deformation in Hangzhou varies significantly with the depth of the foundation pit, but the influence of the depth of the foundation pit on the wall deformation is considerably less than that in Shanghai and Ningbo. The corresponding position of the maximum lateral deformation in the excavation depth increases linearly with the excavation depth of the foundation pit, and the corresponding position of the lateral deformation of the diaphragm wall in Shanghai is more affected by the excavation depth of the foundation pit. The lateral deformation of the diaphragm wall increases rapidly in the range of 0 H–0.5 H, and the maximum lateral deformation occurs at 0.5 H–1.1 H.

Research on Deformation Law of Deep Foundation Pit of Station in Core Region of Saturated Soft Loess Based on Monitoring

“…Due to the upper concrete and the lower soil support, the deformation at the lower ends of the continuous underground wall is smaller. It can be seen from the figure that as the excavation depth of the foundation pit increases, the deformation of the underground continuous wall is "serrated," which is different from the general "bow" [14]. is is because the preaxial force of the steel support is too large, resulting in the continuous underground wall not being able to bear the force together with the steel support.…”

“…In recent years, many scholars have analyzed the monitoring of different types of deep foundation pits in loess and soft soil areas. Clough, Long, Moormann C, and others carried out a classification study on the deformation of different foundation pits around the world and obtained the deformation law of foundation pits during construction [9][10][11]; Mei and Yang analyzed the deformation characteristics and influencing factors of foundation pits in Xi'an, Shanghai, Ningbo, Hangzhou, and other regions, respectively [12][13][14]; Zhou Yong, Ren Jianxi, Liu, Zhi, Li Zhe, Eibaz, and Wang Guohui studied and analyzed the monitoring data of pile displacement, surface settlement outside the pit, supporting axial force, and groundwater level during the excavation of the foundation pit [15][16][17][18][19][20][21]; Xu Jian and Zhang, respectively, compared numerical simulation and monitoring data of foundation pit excavation to analyze the deformation characteristics of foundation pit [22,23]; Zhang and Di studied the influence of the enclosure structure on ground settlement [24,25]; Farzi et al [26] conducted a systematic survey of the complex geotechnical characteristics of Ahwaz, and the displacement value during construction and excavation was checked and evaluated; Wang et al [27] analyzed the influence of soil structural changes on the horizontal displacement of the retaining structure wall, ground settlement, and adjacent subway tunnels during the excavation of the foundation pit; and Liu et al [28] analyzed the influence mechanism of rainfall on the deformation of the soft soil foundation pit support structure.…”

Investigation on Dewatering of a Deep Shaft in Strong Permeable Sandy Pebble Strata on the Bank of the Yellow River

“…The authors would like to thank the financial support from China Railway First Survey and Design Institute Group Co., Ltd. and Lanzhou Rail Transit Co., Ltd. (Grant No. [13][14][15][16][17]. Thanks are due to the China Railway First Survey and Design Institute Group Co., Ltd. and the China Railway No.14 Engineering Group Co., Ltd. for providing great assistance in field water table observation and land subsidence observation.…”

“…Liu et al [10] proposed inflow prediction formulas for excavation pits with partial penetrating curtains in high-permeability aquifers. Other researchers [11][12][13] focused on the deformation mechanism of diaphragm wall and ground settlement induced by dewatering. Zeng et al [14] and Zeng et al [15] investigated ground settlement caused by preexcavation dewatering.…”

The Deformation Analysis of a Deep Frame Top‐Down Excavation in Downtown Shanghai Based on the 3D FEM

“…Moreover, it will take a long period of time to construct the floor, such as form work, rebar, concreting, and curing, which leads to the extension of construction period as well as duration of unpropped wall exposure. Significant retaining wall deflections and ground movements may be induced due to the long construction period and unpropped wall exposure period caused by deep excavations in Shanghai in soft clay with high water content, low strength, and high rheology [9][10][11][12]. e frame top-down method (FTDM) is a special top-down method which applies beams as supports to make full use of advantages of both the BUM and the TDM.…”