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Wall movement during de-watering inside a diaphragm wall before soil excavation

Wall movement during de-watering inside a diaphragm wall before soil excavation
Wall movement during de-watering inside a diaphragm wall before soil excavation
Significant movement of in-situ retaining walls is usually assumed to begin with bulk excavation. However, an increasing number of case studies show that lowering the pore water pressures inside a diaphragm wall-type basement enclosure prior to bulk excavation can cause wall movements in the order of some centimeters. This paper describes the results of a laboratory-scale experiment carried out to explore mechanisms of in situ retaining wall movement associated with dewatering inside the enclosure prior to bulk excavation. Dewatering reduces the pore water pressures inside the enclosure more than outside, resulting in the wall moving as an unpropped cantilever supported only by the soil. Lateral effective stresses in the shallow soil behind the wall are reduced, while lateral effective stresses in front of the wall increase. Although the associated lateral movement was small in the laboratory experiment, the movement could be proportionately larger in the field with a less stiff soil and a potentially greater dewatered depth. The implementation of a staged dewatering system, coupled with the potential for phased excavation and propping strategies, can effectively mitigate dewatering-induced wall and soil movements. This approach allows for enhanced stiffness of the wall support system, which can be dynamically adjusted based on real-time displacement monitoring data when necessary.
Deep excavation, Dewatering, Diaphragm wall deflection, Groundwater control, Laboratory experiment
2467-9674
355-368
Zeng, Chao-Feng
3b73e33b-0411-4721-9f4c-f2946a15a427
Powrie, William
600c3f02-00f8-4486-ae4b-b4fc8ec77c3c
Xu, Chang-Jie
ce52ceee-9c9c-4e51-9a45-927383baddaa
Xue, Xiu-Li
a3ce78d3-d9dd-407e-8f0f-3d227cce93b0
Zeng, Chao-Feng
3b73e33b-0411-4721-9f4c-f2946a15a427
Powrie, William
600c3f02-00f8-4486-ae4b-b4fc8ec77c3c
Xu, Chang-Jie
ce52ceee-9c9c-4e51-9a45-927383baddaa
Xue, Xiu-Li
a3ce78d3-d9dd-407e-8f0f-3d227cce93b0

Zeng, Chao-Feng, Powrie, William, Xu, Chang-Jie and Xue, Xiu-Li (2025) Wall movement during de-watering inside a diaphragm wall before soil excavation. Underground Space, 22, 355-368. (doi:10.1016/j.undsp.2025.01.003).

Record type: Article

Abstract

Significant movement of in-situ retaining walls is usually assumed to begin with bulk excavation. However, an increasing number of case studies show that lowering the pore water pressures inside a diaphragm wall-type basement enclosure prior to bulk excavation can cause wall movements in the order of some centimeters. This paper describes the results of a laboratory-scale experiment carried out to explore mechanisms of in situ retaining wall movement associated with dewatering inside the enclosure prior to bulk excavation. Dewatering reduces the pore water pressures inside the enclosure more than outside, resulting in the wall moving as an unpropped cantilever supported only by the soil. Lateral effective stresses in the shallow soil behind the wall are reduced, while lateral effective stresses in front of the wall increase. Although the associated lateral movement was small in the laboratory experiment, the movement could be proportionately larger in the field with a less stiff soil and a potentially greater dewatered depth. The implementation of a staged dewatering system, coupled with the potential for phased excavation and propping strategies, can effectively mitigate dewatering-induced wall and soil movements. This approach allows for enhanced stiffness of the wall support system, which can be dynamically adjusted based on real-time displacement monitoring data when necessary.

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Accepted/In Press date: 17 January 2025
e-pub ahead of print date: 3 April 2025
Published date: 15 April 2025
Keywords: Deep excavation, Dewatering, Diaphragm wall deflection, Groundwater control, Laboratory experiment

Identifiers

Local EPrints ID: 501483
URI: http://eprints.soton.ac.uk/id/eprint/501483
ISSN: 2467-9674
PURE UUID: cacf91d7-3ab1-46a5-b45f-4a568d128f7a
ORCID for William Powrie: ORCID iD orcid.org/0000-0002-2271-0826

Catalogue record

Date deposited: 02 Jun 2025 16:55
Last modified: 22 Aug 2025 01:39

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Contributors

Author: Chao-Feng Zeng
Author: William Powrie ORCID iD
Author: Chang-Jie Xu
Author: Xiu-Li Xue

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