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Article: Modified Theis equation by considering the bending effect of the confining unit

TitleModified Theis equation by considering the bending effect of the confining unit
Authors
KeywordsBending Effect
Confined Aquifer
Modified Theis Equation
Pumping Test
Theis Equation
Issue Date2004
PublisherPergamon. The Journal's web site is located at http://www.elsevier.com/locate/advwatres
Citation
Advances In Water Resources, 2004, v. 27 n. 10, p. 981-990 How to Cite?
AbstractThe Theis equation has been widely used to study the transient movement of groundwater as a result of pumping in a confined aquifer. It is well known that the observed drawdown at early times has an obvious departure from the theoretical drawdown based on the Theis equation. The Theis equation was derived under the assumption that total stress in the aquifer was constant and the mechanical behavior of the confining unit was neglected. However, most geological formations, especially those which are well consolidated, have rigidity and therefore may bend like a plate to a certain extent. The increase in the effective stress in the aquifer due to pumping may not contribute entirely to the compression of the aquifer, but may be partially cancelled out by bending of the overlying aquitard. This means only a part of the total stress is used to compact the aquifer, or the aquifer cannot produce as much water as estimated from the Theis equation. This paper investigated the impact of the bending effect of the confining unit on drawdown. An analytical model which couples flow in the aquifer and bending of the confining unit was presented. The theory is based on elastic plates and solutions were given to the drawdown of groundwater level and deflection of the overlying formation. The drawdown estimated from the new equation was compared with that from the Theis equation. It can be concluded that drawdown from the Theis equation is less than the drawdown predicted by including the bending effect of the confining unit. Both a hypothetical example and a field pumping test in Shandong Province, China, were used to demonstrate the bending effect of the confining unit in the analysis of pumping test data. This paper demonstrated that the initial disagreement between observed drawdown and the Theis solution could be caused by the bending effect of the confining unit, a phenomenon not well addressed in traditional pumping test analysis. A quantitative understanding of this phenomenon can provide improved guidelines for analyzing drawdown data in a confined aquifer. © 2004 Elsevier Ltd. All rights reserved.
Persistent Identifierhttp://hdl.handle.net/10722/151279
ISSN
2015 Impact Factor: 4.349
2015 SCImago Journal Rankings: 2.408
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorWang, XSen_US
dc.contributor.authorChen, CXen_US
dc.contributor.authorJiao, JJen_US
dc.date.accessioned2012-06-26T06:19:57Z-
dc.date.available2012-06-26T06:19:57Z-
dc.date.issued2004en_US
dc.identifier.citationAdvances In Water Resources, 2004, v. 27 n. 10, p. 981-990en_US
dc.identifier.issn0309-1708en_US
dc.identifier.urihttp://hdl.handle.net/10722/151279-
dc.description.abstractThe Theis equation has been widely used to study the transient movement of groundwater as a result of pumping in a confined aquifer. It is well known that the observed drawdown at early times has an obvious departure from the theoretical drawdown based on the Theis equation. The Theis equation was derived under the assumption that total stress in the aquifer was constant and the mechanical behavior of the confining unit was neglected. However, most geological formations, especially those which are well consolidated, have rigidity and therefore may bend like a plate to a certain extent. The increase in the effective stress in the aquifer due to pumping may not contribute entirely to the compression of the aquifer, but may be partially cancelled out by bending of the overlying aquitard. This means only a part of the total stress is used to compact the aquifer, or the aquifer cannot produce as much water as estimated from the Theis equation. This paper investigated the impact of the bending effect of the confining unit on drawdown. An analytical model which couples flow in the aquifer and bending of the confining unit was presented. The theory is based on elastic plates and solutions were given to the drawdown of groundwater level and deflection of the overlying formation. The drawdown estimated from the new equation was compared with that from the Theis equation. It can be concluded that drawdown from the Theis equation is less than the drawdown predicted by including the bending effect of the confining unit. Both a hypothetical example and a field pumping test in Shandong Province, China, were used to demonstrate the bending effect of the confining unit in the analysis of pumping test data. This paper demonstrated that the initial disagreement between observed drawdown and the Theis solution could be caused by the bending effect of the confining unit, a phenomenon not well addressed in traditional pumping test analysis. A quantitative understanding of this phenomenon can provide improved guidelines for analyzing drawdown data in a confined aquifer. © 2004 Elsevier Ltd. All rights reserved.en_US
dc.languageengen_US
dc.publisherPergamon. The Journal's web site is located at http://www.elsevier.com/locate/advwatresen_US
dc.relation.ispartofAdvances in Water Resourcesen_US
dc.subjectBending Effecten_US
dc.subjectConfined Aquiferen_US
dc.subjectModified Theis Equationen_US
dc.subjectPumping Testen_US
dc.subjectTheis Equationen_US
dc.titleModified Theis equation by considering the bending effect of the confining uniten_US
dc.typeArticleen_US
dc.identifier.emailJiao, JJ:jjiao@hku.hken_US
dc.identifier.authorityJiao, JJ=rp00712en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1016/j.advwatres.2004.08.007en_US
dc.identifier.scopuseid_2-s2.0-6444239311en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-6444239311&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume27en_US
dc.identifier.issue10en_US
dc.identifier.spage981en_US
dc.identifier.epage990en_US
dc.identifier.isiWOS:000225018100003-
dc.publisher.placeUnited Kingdomen_US
dc.identifier.scopusauthoridWang, XS=8118576100en_US
dc.identifier.scopusauthoridChen, CX=14027847300en_US
dc.identifier.scopusauthoridJiao, JJ=7102382963en_US

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