Solution for Soil Vapor Extraction from a Pressure-Controlled Well
Publication: Journal of Environmental Engineering
Volume 143, Issue 6
Abstract
This paper presents a new solution for a soil venting problem, in which a vertical, partially penetrating well is operated at a fixed pressure under covered, uncovered, or leaking ground surface conditions. The method of domain decomposition is applied to solve the problem of a mixed-type boundary condition imposed along a well screen, which in previous solutions was usually handled by discretization of the screen. The new solution is also capable of predicting the flow field beneath the well bottom, which is commonly neglected by other solutions. The authors found that the present solution may predict different pressure distributions from those given by a solution employing a constant flux rate at a well screen. The radius of influence for soil vapor extraction (SVE) operations is strongly affected by the radial permeability, the vertical permeability, and the ratio between the two. Vacuum pressure values were predicted with the proposed solution and compared against measurements at different observation wells and depths under venting tests at a former SVE-operated site. The measured vacuum pressure and gas flow velocity values around the wells were found to be substantially lower than the predicted values. Thus, the wellbore soils of the site were suspected to be positive skin zones.
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Acknowledgments
Funding of this work was provided by the ROC Ministry of Science and Technology under Contract 101-2221-E-035-030-MY2 and 103-2221-E-035-002-MY3. The authors would like to thank Yuroa Lin, Yong-tai Sun, and Raili Chung for their assistance in conducting the field experiments.
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Published In
Journal of Environmental Engineering
Volume 143 • Issue 6 • June 2017
Copyright
©2017 American Society of Civil Engineers.
History
Received: Mar 15, 2015
Accepted: Dec 1, 2016
Published ahead of print: Feb 21, 2017
Published online: Feb 22, 2017
Published in print: Jun 1, 2017
Discussion open until: Jul 22, 2017
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