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Investigation of mineral bentonite barriers optimized for hydraulic compatibility and shear strength

dc.contributor.authorJacob, Samuel Robert, author
dc.contributor.authorScalia, Joseph, IV, advisor
dc.contributor.authorBareither, Christopher, committee member
dc.contributor.authorSanford, William, committee member
dc.date.accessioned2024-12-23T11:59:35Z
dc.date.available2024-12-23T11:59:35Z
dc.date.issued2024
dc.description.abstractLiners are a foundation tool of environmental geotechnics. Modern liners are constructed using natural and polymeric materials with low hydraulic conductivity (k), often at the expense of having low shear strength. These liners are often subject to high stresses on the order of hundreds to thousands of kPa which can lead to decreased performance over time and failure of the liner in shear. This research investigates mineral-bentonite mixtures in the context of high-stress liner applications. Mixtures containing varying amounts of sand, bentonite, and rock flour were created in the laboratory. Hydraulic conductivity of specimens was measured using flexible wall permeameters in accordance with ASTM D7100 using either de-ionized (DI) water, 10 mM, or 500 mM CaCl2 solutions. Specimens were removed from permeameters once k termination criteria were met and subsequently tested in direct shear at either 35 kPa or 825 kPa effective stress to obtain peak (φ´peak) and ultimate (φ´u) friction angles. Mixtures generally achieved a final k of 10- 9 m/s with bentonite contents of 4.5% and 8% when permeated with DI water and 10 mM CaCl2 solutions, respectively. Adding rock flour to mixtures containing bentonite lowered final equilibrium k but rock flour was not suitable as a complete replacement for bentonite. At 35 kPa effective stress, shear strength increased until approximately 15% equivalent fines, whereas shear strength was relatively constant at 825 kPa with increasing equivalent fines from 0-15%. At 825 kPa, shear strength substantially dropped at equivalent fines greater than 15%, which is the approximate percentage of fines that the sand matrix began to lose grain-grain contact due to the displacement by fines. The results from this study highlight that while low k and high φ´ can be achieved, even at high effective stresses, care and precision during design and construction of a mineral-bentonite barrier is required to ensure that all design criteria are met.
dc.format.mediumborn digital
dc.format.mediummasters theses
dc.identifierJacob_colostate_0053N_18766.pdf
dc.identifier.urihttps://hdl.handle.net/10217/239819
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado State University. Libraries
dc.relation.ispartof2020-
dc.rightsCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.
dc.titleInvestigation of mineral bentonite barriers optimized for hydraulic compatibility and shear strength
dc.typeText
dcterms.rights.dplaThis Item is protected by copyright and/or related rights (https://rightsstatements.org/vocab/InC/1.0/). You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).
thesis.degree.disciplineCivil and Environmental Engineering
thesis.degree.grantorColorado State University
thesis.degree.levelMasters
thesis.degree.nameMaster of Science (M.S.)

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