Repository logo
 

Selected factors affecting measurement of the hydraulic conductivity of geosynthethic clay liners

Simple item page
dc.contributor.authorPopang, Monika Aprianti, author
dc.contributor.authorScalia, Joseph, IV, advisor
dc.contributor.authorShackelford, Charles D., advisor
dc.contributor.authorRonayne, Michael J., committee member
dc.date.accessioned2018-09-10T20:05:27Z
dc.date.available2019-09-06T20:04:15Z
dc.date.issued2018
dc.description.abstractGeosynthetic clay liners (GCLs) are thin (~7 to 10 mm), factory manufactured hydraulic barriers typically comprising a layer of sodium bentonite sandwiched between two geotextiles. Upon hydration and permeation with water at low effective stress (σ´) (e.g., typically ≤ ~30 kPa [4 psi]), the bentonite in GCLs, which typically is initially in an air-dried condition, swells to form a low hydraulic conductivity (k) layer (i.e., k of ~2-3×10-11 m/s) that is suitable for use as a barrier in hydraulic and chemical containment applications. However, adverse physico-chemical interactions between the bentonite in GCLs and both the hydrating and permeating liquids may yield substantially higher k than what is typically acceptable for design (i.e., k ≤ 1×10-9 m/s). Accordingly, this study pertained to evaluating the effects of the type of permeant liquid and the magnitude of σ´ on the measurement of k of two GCLs, a higher grade needle-punched (HGN) GCL and a lower grade needle-punched (LGN) GCL. The permeant liquids included tap water (TW), conservative water (CW), and several calcium chloride (CaCl2) solutions, and the σ´ included 27.3 kPa (4 psi) and 61.7 kPa (9 psi). The resulting measured ratios of final k for the HGN GCL relative to the LGN GCL (kf HGN/kf LGN) at ~24-27 kPa (4 psi) were ~28 (1.5 orders of magnitude), ~194 (2.3 orders of magnitude), and ~1975 (3.3 orders of magnitude) based on permeation with 5, 10, and 20 mM CaCl2, respectively. Thus, an increase in the fiber bundles density of the needle-punched fibers of the GCL adversely impacted the k of this GCL. Tests using dyed permeant liquids revealed that the high k was attributable to preferential flow along the fiber bundles of the GCL. Also, an increase in σ´ from 27.3 kPa (4 psi) to 61.7 kPa (9 psi) did not appreciably impact the measured k. Finally, permeation of the HGN GCL with the more dilute liquids (TW, CW, 1 and 2.5 mM CaCl2) resulted in consistently low k of ~2×10-11 m/s. The results of this study also illustrate the importance of achieving not only hydraulic equilibrium but also chemical equilibrium before terminating the k tests, as the measured k at hydraulic equilibrium based on the higher ionic strength solutions (i.e., 5, 10, and 20 mM CaCl2) typically were lower and, therefore, more unconservative than the measured k at chemical equilibrium. This study also evaluated the use of different methods to measure the k of the HGN GCL, including the falling headwater, constant tailwater method and the constant rate-of-flow method using a flow pump with pressure transducers. The results indicated that neither method proved substantially effective at achieving chemical equilibrium faster, although employing higher hydraulic gradient (i) was shown to expedite the attainment of chemical equilibrium. This result is associated with flushing action in the intergranular pore spaces that effectively maintaining higher concentration gradient between within and outside the bentonite granules. Also, prehydrating the specimens with the permeant liquid tended to enhance the osmotic swell of the bentonite resulting in a lower k at lower pore volumes of flow. Finally, diffusion of solutes from interlayer to intergranular pore spaces within the GCL specimens permeated with CW was shown to be the rate-limiting mechanism for attaining chemical equilibrium.
dc.format.mediumborn digital
dc.format.mediummasters theses
dc.identifierPopang_colostate_0053N_15037.pdf
dc.identifier.urihttps://hdl.handle.net/10217/191443
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado State University. Libraries
dc.relation.ispartof2000-2019
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.titleSelected factors affecting measurement of the hydraulic conductivity of geosynthethic clay liners
dc.typeText
dcterms.embargo.expires2019-09-06
dcterms.embargo.terms2019-09-06
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.)

Files

Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
Popang_colostate_0053N_15037.pdf
Size:
19.17 MB
Format:
Adobe Portable Document Format
Description:
Download

Collections

2000-2019
Theses and Dissertations