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Field trial of an ejector well dewatering system at Conwy, North Wales

Powrie, W. and Roberts, T.O.L. (1990) Field trial of an ejector well dewatering system at Conwy, North Wales Quarterly Journal of Engineering Geology and Hydrogeology, 23, pp. 169-185. (doi:10.1144/?GSL.QJEG.1990.023.02.06).

Record type: Article

Abstract

An ejector or water jet pump is particularly suitable for pore water pressure relief applications in fine soils since it can operate at relatively low pumped flowrates, creating a vacuum at depth inside the well. A field trial of an ejector well dewatering system was carried out in laminated glacial lake deposits at Conwy, North Wales, in connection with the construction of the A55 Conwy Crossing. During the trial groundwater extraction flow rates and pore water pressures were monitored. Some of the ejector wells terminated in the bedrock underlying the lake deposits: in many of these, the groundwater extraction flow rates were high and the drawdowns achieved were relatively low. Back-analysis using conventional methods modelled closely the observed response of near-by piezometers. On the other hand, wells terminating in the lake deposits yielded low groundwater extraction flow rates and vacuums at about 500 millibar developed. In this case, conventional analysis substantially overpredicted both the rate and magnitude of drawdown in the surrounding ground. The reasons for this are as yet uncertain: nonetheless, the results of the trial demonstrate clearly the influence of the hydraulic boundary conditions on the performance of a dewatering system.

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Published date: 1990

Identifiers

Local EPrints ID: 74889
URI: http://eprints.soton.ac.uk/id/eprint/74889
ISSN: 1470-9236
PURE UUID: 2b3f122a-c111-4568-a5e8-8278c10a961c
ORCID for W. Powrie: ORCID iD orcid.org/0000-0002-2271-0826

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Date deposited: 11 Mar 2010
Last modified: 18 Jul 2017 23:44

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