dc.contributor.author	Baxter, Diane Yamane	en
dc.contributor.committeechair	Filz, George M.	en
dc.contributor.committeemember	Batra, Romesh C.	en
dc.contributor.committeemember	Duncan, James Michael	en
dc.contributor.committeemember	Kuppusamy, Thangavelu	en
dc.contributor.committeemember	Mitchell, James K.	en
dc.contributor.department	Civil Engineering	en
dc.date.accessioned	2014-03-14T20:10:17Z	en
dc.date.adate	2000-04-25	en
dc.date.available	2014-03-14T20:10:17Z	en
dc.date.issued	2000-04-14	en
dc.date.rdate	2001-04-25	en
dc.date.sdate	2000-04-21	en
dc.description.abstract	A soil-bentonite cutoff wall is a type of subsurface vertical barrier constructed by back-filling a trench with a mixture of soil, bentonite, and water. Although soil-bentonite cutoff walls are common, their mechanical behavior is not well understood. Current design procedures do not consider the final stress state of the consolidated soil-bentonite backfill or deformations in adjacent ground. The final stress state in the completed wall is important because it influences the hydraulic conductivity of the cutoff (Barrier 1995), the cutoff's susceptibility to hydraulic fracture, and the magnitude of deformations adjacent to the cutoff wall. Deformations adjacent to the cutoff wall can be significant and can cause damage to adjacent structures. The objectives of this research are to 1) add to the current body of knowledge of the properties of soil-bentonite mixtures, 2) evaluate constitutive models and select a model to represent soil-bentonite, 3) model a soil-bentonite cutoff wall using finite elements, and 4) investigate the influence of several factors on the deformations in adjacent ground. These objectives were met by first summarizing information from the literature on soil-bentonite properties and then performing a laboratory testing program on different soil-bentonite mixtures. Five constitutive models were evaluated to determine how well they match the data from the laboratory testing program. A model referred to as the RS model was chosen to best represent soil-bentonite, and provided a good match of the soil-bentonite behavior. The RS model, which is a special case of a more complicated existing model, is a non-associative Modified Cam Clay type model that has parameters to change the yield surface and plastic potential surface into ellipses of varying shapes. The RS model was implemented into the finite element program SAGE. A finite element model was developed using SAGE to simulate all stages of construction of a soil-bentonite cutoff wall including excavation of a trench under bentonite-water slurry, replacement of the bentonite-water slurry with soil-bentonite backfill, and consolidation of the soil-bentonite backfill. The model was calibrated with a well-documented case history, and predicted deformations in adjacent ground were close to measured deformations. Evaluation of the model indicates that there is good confidence in the prediction of deformations in adjacent ground, but there is lower confidence in the predicted stresses in the consolidated soil-bentonite and settlement of the backfill in the trench. A parametric study was then performed using the finite element model assuming sand sites of varying density and OCR. Deformations in adjacent ground were calculated for various soil conditions, soil-bentonite properties, and trench configurations. A correlation was found between maximum calculated settlement in adjacent ground and factor of safety against trench	en
dc.description.degree	Ph. D.	en
dc.identifier.other	etd-04212000-15560035	en
dc.identifier.sourceurl	http://scholar.lib.vt.edu/theses/available/etd-04212000-15560035/	en
dc.identifier.uri	http://hdl.handle.net/10919/27079	en
dc.publisher	Virginia Tech	en
dc.relation.haspart	appendix_b.PDF	en
dc.relation.haspart	vita.pdf	en
dc.relation.haspart	Ch2.PDF	en
dc.relation.haspart	Ch1.PDF	en
dc.relation.haspart	Ch8.PDF	en
dc.relation.haspart	ch7.PDF	en
dc.relation.haspart	Ch5.PDF	en
dc.relation.haspart	Ch3.PDF	en
dc.relation.haspart	Ch4.PDF	en
dc.relation.haspart	references.pdf	en
dc.relation.haspart	appendix_c2.PDF	en
dc.relation.haspart	etd.pdf	en
dc.relation.haspart	Ch6.PDF	en
dc.relation.haspart	appendix_a.PDF	en
dc.relation.haspart	appendix_c1.PDF	en
dc.rights	In Copyright	en
dc.rights.uri	http://rightsstatements.org/vocab/InC/1.0/	en
dc.subject	soil-bentonite	en
dc.subject	constitutive modeling	en
dc.subject	vertical barrier	en
dc.subject	Finite element method	en
dc.subject	cutoff wall	en
dc.title	Mechanical Behavior of Soil-Bentonite Cutoff Walls	en
dc.type	Dissertation	en
thesis.degree.discipline	Civil Engineering	en
thesis.degree.grantor	Virginia Polytechnic Institute and State University	en
thesis.degree.level	doctoral	en
thesis.degree.name	Ph. D.	en

Mechanical Behavior of Soil-Bentonite Cutoff Walls

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