Case study of post uplift in deep excavation of a subway station in thick soft clay using long pile foundations
There is growing engineering concern about the base heave and post uplift phenomena in deep excavation in soft clay, which may pose a risk of instability of retaining systems. The purpose here is to conduct a detailed case study on the post uplift observed in a 17.6-meter-deep braced excavation of a...
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| Format: | Article |
| Language: | English |
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KeAi Communications Co., Ltd.
2022-04-01
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| Series: | Underground Space |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2467967421000702 |
| _version_ | 1827887987651772416 |
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| author | Yanbin Gao Zhouxiang Ding |
| author_facet | Yanbin Gao Zhouxiang Ding |
| author_sort | Yanbin Gao |
| collection | DOAJ |
| description | There is growing engineering concern about the base heave and post uplift phenomena in deep excavation in soft clay, which may pose a risk of instability of retaining systems. The purpose here is to conduct a detailed case study on the post uplift observed in a 17.6-meter-deep braced excavation of a subway station in thick soft clay (total thickness up to 42 m) in Shanghai. In this case, a large uplift up to 87 mm unexpectedly developed for the post founded on a 30-meter-long pile foundation. Efforts were first made to examine the complex relationships between the post uplift with the excavation depth (H), Terzaghi’s safety factor against base heave (Fs) and maximum deflection of retaining wall. A simplified approach for soil-post-strut interaction analysis was then proposed and used for quantitative research. The working characteristics of the long pile foundation under low safety factor against base heave (Fs < 1.5) are summarized as following: (a) the back-analyzed neutral plane, where soil uplift equals the post uplift, lies at approximately 0.68 times the pile length from the pile top; (b) deep soil movement below the neutral plane results in the observed post uplift; (c) strut reaction plays a minor role in the restriction of post uplift. The influence of base treatment and excavation/construction procedures on post uplift and the principles of pile foundation design are also discussed in this paper. |
| first_indexed | 2024-03-12T20:27:22Z |
| format | Article |
| id | doaj.art-79385873334d4a18842b1b93b30aa44c |
| institution | Directory Open Access Journal |
| issn | 2467-9674 |
| language | English |
| last_indexed | 2024-03-12T20:27:22Z |
| publishDate | 2022-04-01 |
| publisher | KeAi Communications Co., Ltd. |
| record_format | Article |
| series | Underground Space |
| spelling | doaj.art-79385873334d4a18842b1b93b30aa44c2023-08-02T00:23:17ZengKeAi Communications Co., Ltd.Underground Space2467-96742022-04-0172254267Case study of post uplift in deep excavation of a subway station in thick soft clay using long pile foundationsYanbin Gao0Zhouxiang Ding1Department of Geotechnical Engineering, Tongji University, #1239 Siping Road, Shanghai 200092, China; Corresponding author.Department of Mechanical Engineering, University of Saskatchewan, CanadaThere is growing engineering concern about the base heave and post uplift phenomena in deep excavation in soft clay, which may pose a risk of instability of retaining systems. The purpose here is to conduct a detailed case study on the post uplift observed in a 17.6-meter-deep braced excavation of a subway station in thick soft clay (total thickness up to 42 m) in Shanghai. In this case, a large uplift up to 87 mm unexpectedly developed for the post founded on a 30-meter-long pile foundation. Efforts were first made to examine the complex relationships between the post uplift with the excavation depth (H), Terzaghi’s safety factor against base heave (Fs) and maximum deflection of retaining wall. A simplified approach for soil-post-strut interaction analysis was then proposed and used for quantitative research. The working characteristics of the long pile foundation under low safety factor against base heave (Fs < 1.5) are summarized as following: (a) the back-analyzed neutral plane, where soil uplift equals the post uplift, lies at approximately 0.68 times the pile length from the pile top; (b) deep soil movement below the neutral plane results in the observed post uplift; (c) strut reaction plays a minor role in the restriction of post uplift. The influence of base treatment and excavation/construction procedures on post uplift and the principles of pile foundation design are also discussed in this paper.http://www.sciencedirect.com/science/article/pii/S2467967421000702Post upliftDeep excavationField observationsNeutral planeSoft clayPile foundation |
| spellingShingle | Yanbin Gao Zhouxiang Ding Case study of post uplift in deep excavation of a subway station in thick soft clay using long pile foundations Underground Space Post uplift Deep excavation Field observations Neutral plane Soft clay Pile foundation |
| title | Case study of post uplift in deep excavation of a subway station in thick soft clay using long pile foundations |
| title_full | Case study of post uplift in deep excavation of a subway station in thick soft clay using long pile foundations |
| title_fullStr | Case study of post uplift in deep excavation of a subway station in thick soft clay using long pile foundations |
| title_full_unstemmed | Case study of post uplift in deep excavation of a subway station in thick soft clay using long pile foundations |
| title_short | Case study of post uplift in deep excavation of a subway station in thick soft clay using long pile foundations |
| title_sort | case study of post uplift in deep excavation of a subway station in thick soft clay using long pile foundations |
| topic | Post uplift Deep excavation Field observations Neutral plane Soft clay Pile foundation |
| url | http://www.sciencedirect.com/science/article/pii/S2467967421000702 |
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