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Influence of large scale inhomogeneities on a construction dewatering system in chalk

Influence of large scale inhomogeneities on a construction dewatering system in chalk
Influence of large scale inhomogeneities on a construction dewatering system in chalk
Large-scale anisotropy and inhomogeneities resulting from the presence of fissures, fractures and high-permeability zones can have a major impact on local groundwater flows, and affect significantly the performance of a construction dewatering system. A groundwater model for the HS1 Channel tunnel rail link Thames tunnel southern approach excavation is used to show that the observed performance of the construction dewatering system cannot adequately be explained unless such features are incorporated. While experience suggested that such features were likely to be present in this geological setting, at the design stage there was significant uncertainty regarding their scale. Groundwater flow modelling enables the location and extent of the inhomogeneities present to be deduced in some detail. Features such as highly permeable zones might be identified by more thorough site investigation, inclduing the more widespread use of pumping tests. However, the influence of anisotropy is harder to establish, primarily because its effect is most significant once a horizontal flow barrier (for example, a retaining wall) is in place, which is generally not the case during site investigation.
numerical modelling, excavation, permeability, geology, groundwater
0016-8505
635-649
Bevan, M.A.
20b53e26-0581-40e5-9c76-8aeff845966e
Powrie, W.
600c3f02-00f8-4486-ae4b-b4fc8ec77c3c
Roberts, T.O.L.
ef394b99-fbc6-4d7a-8ea9-7716a4f1b78e
Bevan, M.A.
20b53e26-0581-40e5-9c76-8aeff845966e
Powrie, W.
600c3f02-00f8-4486-ae4b-b4fc8ec77c3c
Roberts, T.O.L.
ef394b99-fbc6-4d7a-8ea9-7716a4f1b78e

Bevan, M.A., Powrie, W. and Roberts, T.O.L. (2010) Influence of large scale inhomogeneities on a construction dewatering system in chalk. Géotechnique, 60 (8), 635-649. (doi:10.1680/geot.9.P.010).

Record type: Article

Abstract

Large-scale anisotropy and inhomogeneities resulting from the presence of fissures, fractures and high-permeability zones can have a major impact on local groundwater flows, and affect significantly the performance of a construction dewatering system. A groundwater model for the HS1 Channel tunnel rail link Thames tunnel southern approach excavation is used to show that the observed performance of the construction dewatering system cannot adequately be explained unless such features are incorporated. While experience suggested that such features were likely to be present in this geological setting, at the design stage there was significant uncertainty regarding their scale. Groundwater flow modelling enables the location and extent of the inhomogeneities present to be deduced in some detail. Features such as highly permeable zones might be identified by more thorough site investigation, inclduing the more widespread use of pumping tests. However, the influence of anisotropy is harder to establish, primarily because its effect is most significant once a horizontal flow barrier (for example, a retaining wall) is in place, which is generally not the case during site investigation.

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More information

Published date: August 2010
Keywords: numerical modelling, excavation, permeability, geology, groundwater
Organisations: Civil Engineering & the Environment

Identifiers

Local EPrints ID: 186155
URI: http://eprints.soton.ac.uk/id/eprint/186155
ISSN: 0016-8505
PURE UUID: fcb87aa5-21e4-449e-ae6b-1979871a6e91
ORCID for W. Powrie: ORCID iD orcid.org/0000-0002-2271-0826

Catalogue record

Date deposited: 12 May 2011 12:30
Last modified: 31 Jul 2019 00:51

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Contributors

Author: M.A. Bevan
Author: W. Powrie ORCID iD
Author: T.O.L. Roberts

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