Performance of braced excavation in residual soil with groundwater drawdown

Zhang, W. G.; Goh, Anthony Teck Chee; Goh, Kim Huat; Chew, Otard Y.S.; Zhou, Dongbo; Zhang, Runhong

doi:10.1016/j.undsp.2018.03.002

Cited by 64 publications

(18 citation statements)

References 14 publications

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“…Due to some settlement markers being located further away from the wall or on buildings that has more solid foundation, a big range of δ vm /H is observed. Zhang et al [26] reported a quite similar experience to the present study, where δ vm /H was 0.9% and attributed the large ground surface settlements to significant groundwater drawdown.…”

Section: Specific Observations Along Walls E and Fsupporting

confidence: 87%

“…Ignoring these values, the maximum δ vm /δ hm ratio will be 6, still significantly larger than the typical value of 0.5-1.0. Zhang et al [26] reported δ vm /δ hm of 10 and attributed the excessive ground surface settlements to significant groundwater drawdown due to under-drainage mechanism. Therefore, drawing upon the data from the water standpipes at the cut-and-cover tunnel, it is deduced that groundwater drawdown, caused by ground anchor installation that punctured the wall, has led to significant settlement.…”

Section: Relationship Between Maximum Wall Deflections and Maximum Settlementsmentioning

confidence: 99%

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Data-Driven Field Observational Method of a Contiguous Bored Pile Wall System Affected by Accidental Groundwater Drawdown

Chong

Ong

2020

Geosciences

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This paper presents the use of a 700 mm-diameter contiguous bored pile (CBP) wall for a main basement deep excavation project with cut-and-cover tunnel. Due to the presence of cement grout columns between piles behind the CBP wall, the main basement was considered to be ‘impermeable’. However, site observations have shown that installation of ground anchors have unintentionally punctured the water tightness of the wall, creating leakages through the CBP wall and the possibility of localized groundwater lowering, as evidenced by the relatively large settlements. In the absence of cement grout columns at the cut-and-cover tunnel section, immediate groundwater drawdown was observed with the excavation rate. Settlement induced by the excavation and groundwater drawdown only slowed down upon the casting of skinwall to prevent groundwater from flowing through the wall. The accidental groundwater leakage led to small wall deflection. The ratio of maximum settlement to maximum deflection is atypical to those reported in the literature. The analysis also revealed that corner effect is significant with smaller settlement registered at the corners of the wall.

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Section: Specific Observations Along Walls E and Fsupporting

confidence: 87%

Section: Relationship Between Maximum Wall Deflections and Maximum Settlementsmentioning

confidence: 99%

Data-Driven Field Observational Method of a Contiguous Bored Pile Wall System Affected by Accidental Groundwater Drawdown

Chong

Ong

2020

Geosciences

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“…as well as groundwater levels, are primary terms that can remarkably alter the soil-pile responses to heavy external loadings. As an example, saturating the soil can cause soil shear strength reduction, which will influence the pile settlement as well as reducing the pile bearing capacities [48]. Another critical issue that can increase the complexity of soil-pile reactions, as well as load-settlement responses, as highlighted by Chisari et al [49].…”

Section: Pile Movement Monitoringmentioning

confidence: 99%

Determination of Young Elasticity Modulus in Bored Piles Through the Global Strain Extensometer Sensors and Real-Time Monitoring Data

et al. 2019

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For friction piles depending on the friction resistance, accurate prediction of unit skin friction around the pile shaft is the dominant resistance to measure the final bearing capacity of a bored-pile. The present study measures the stress-strain transferring in two instrumented bored-piles (BP #1 & BP# 2) embedded within the soil layer in Kuala Lumpur by real-time monitoring global strain extensometer (GSE) sensors. Two bored-piles (i.e., having 1.80 m and 1.0 m diameters, as well as 36 m and 32 m lengths) have been loaded with two times to their design working loads. Extensive data are analyzed to measure the changes in stress-strain in the bored-pile. The effect of loading and unloading stages on the pile's head and base settlement has been monitored, indicating that Young modulus of elasticity in concrete bored-pile (E c ), average strain, and unit skin friction changed along the bored-pile based on the ground site conditions and stress registered. One example of two case studies with great real-time monitoring data has been provided to further design.

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“…When a joint in a D-wall does contain defects, leakage may occur. If the excavation is below the groundwater table, there is the possibility that water inrush and piping may occur during excavation, resulting in land subsidence and even disaster [ 6 , 7 , 8 , 9 , 10 ]. Furthermore, the bearing capacity of the foundation will decrease with the inrush of groundwater into the excavation zone [ 11 ].…”

Section: Introductionmentioning

confidence: 99%

Application of Fiber Bragg Grating Sensor Technology to Leak Detection and Monitoring in Diaphragm Wall Joints: A Field Study

Zhang

Chen

Zheng

et al. 2021

Sensors

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Joints between diaphragm wall panels are weak spots in wall construction. It is essential that potential leak sites are detected prior to excavation. In this study, a novel leak detection and monitoring system is presented that is based on fiber Bragg grating (FBG) sensing technology. A field study was performed in a deep excavation supported by diaphragm walls (in Hohhot, China) to validate the feasibility and effectiveness of the proposed method. Two schemes were trialed; one using pipes made of stainless steel, and one used a pipeless method. The results of the field study are presented and discussed. They show that potential leak sites in the wall joints could be determined prior to excavation using the proposed detection method. Stainless steel is a good material to use to make the detection tube because it can protect the FBG sensors and heating belts from damage and is more sensitive to water leakage. The field study provides good evidence for the feasibility of the new detection system. It also provides valuable experience for the field application of the system and has generated useful data to use in follow-up work.

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Performance of braced excavation in residual soil with groundwater drawdown

Cited by 64 publications

References 14 publications

Data-Driven Field Observational Method of a Contiguous Bored Pile Wall System Affected by Accidental Groundwater Drawdown

Data-Driven Field Observational Method of a Contiguous Bored Pile Wall System Affected by Accidental Groundwater Drawdown

Determination of Young Elasticity Modulus in Bored Piles Through the Global Strain Extensometer Sensors and Real-Time Monitoring Data

Application of Fiber Bragg Grating Sensor Technology to Leak Detection and Monitoring in Diaphragm Wall Joints: A Field Study

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