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Charles D Shackelford - One of the best experts on this subject based on the ideXlab platform.
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limiting membrane and diffusion behavior of a geosynthetic Clay Liner
Geotextiles and Geomembranes, 2016Co-Authors: Charles D Shackelford, Amara Meier, Kristin M SamplelordAbstract:Abstract Bentonite based geosynthetic Clay Liners (GCLs) are commonly used as chemical containment barriers to minimize liquid flow and contaminant transport. The preference for GCLs relative to other materials for chemical containment include economy of use and superior engineering properties, including low hydraulic conductivity ( k ) and the ability to exhibit semipermeable membrane behavior that restricts the migration of solutes through the bentonite. In the case of low k (e.g., ≤10 −10 m/s), diffusion is likely to be a significant, if not dominant, mechanism of chemical transport. The objective of this study was to evaluate the membrane and diffusion behavior of a GCL in the limit as the salt (KCl) concentration increased to the extent that any observed membrane behavior was destroyed. The results indicated that the observed membrane behavior for the GCL was essentially destroyed when the average KCl concentration across the GCL specimen, C ave , reached 200 mM KCl, which was greater than the value of C ave that would have been predicted on the basis of previous results. The results also indicated that the value of the effective diffusion coefficient, D * , for Cl − at this limiting value for C ave of 200 mM KCl was greater than the value of D * that would have been predicted on the basis of the use of lower values of C ave . However, the differences between the measured and predicted values of D * were relatively minor (≤11.3%), such that the differences likely would be insignificant for most practical applications.
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assessment of consolidation induced contaminant transport for compacted Clay Liner systems
Journal of Geotechnical and Geoenvironmental Engineering, 2016Co-Authors: Patrick J. Fox, Charles D ShackelfordAbstract:AbstractThis paper presents an investigation of the effect of Clay consolidation on contaminant transport through compacted Clay Liner (CCL) and composite geomembrane Liner (GML)/CCL landfill bottom Liner systems. Numerical simulations were conducted using the CST2 model and consider coupled consolidation and contaminant transport with representative geometry, material properties, and applied stress conditions. Simulation results indicate that, depending on conditions, consolidation can have important effects on contaminant breakthrough time, mass flux, cumulative mass outflow, and concentration distribution within the CCL, not only during the course of the consolidation process but also long after consolidation has completed. In general, the effects of CCL consolidation increase with increasing CCL thickness, increasing magnitude of applied stress, decreasing loading time, increasing CCL organic carbon fraction, and increasing variation of effective diffusion coefficient. Traditional advective-dispersive...
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restricted salt diffusion in a geosynthetic Clay Liner
Environmental geotechnics, 2015Co-Authors: Michael A Malusis, Jong-beom Kang, Charles D ShackelfordAbstract:The influence of semipermeable membrane behaviour on salt diffusion through a geosynthetic Clay Liner (GCL) was investigated by conducting multi-stage membrane tests on four GCL specimens at different effective stresses (σ′ = 34·5–242 kPa) in flexible-wall cells. Each test was conducted by circulating five source potassium chloride solutions, sequentially from lowest to highest concentration (Co = 3·9, 6·0, 8·7, 20, 47 mM), across the top specimen boundary, while circulating de-ionized water across the bottom boundary. Membrane efficiency coefficients (ω) were determined from differential pressure measurements, and effective salt-diffusion coefficients (Ds*) were inferred from boundary electrical conductivities. Increases in Ds* with increasing Co were observed for all specimens and were correlated to decreases in ω. In each case, Ds* decreased linearly toward zero as ω → 1, regardless of the applied σ′. These results support the hypothesis from pore-scale physical modelling that Ds* for GCLs exhibiting m...
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Consolidation enhanced membrane behavior of a geosynthetic Clay Liner
Geotextiles and Geomembranes, 2011Co-Authors: Jong-beom Kang, Charles D ShackelfordAbstract:Semipermeable membrane behavior in Clays refers to the ability of Clays to restrict the migration of solutes. Thus, membrane behavior represents a potential benefit to the containment function of Clay barriers used for hydraulic containment applications. In this regard, the potential influence of consolidation effective stress, s 0 , on the membrane behavior of a geosynthetic Clay Liner (GCL) containing sodium bentonite was evaluated in the laboratory by establishing differences in salt (KCl) concentrations ranging from 3.9 to 47 mM across specimens of the GCL in a flexible-wall cell under closed-system boundary conditions. The membrane behavior exhibited by the GCL was enhanced via consolidation such that an increase in s 0 from 34.5 kPa (5 psi) to 241 kPa (35 psi) correlated with an increase in membrane efficiency from 0.015 (1.5%) to 0.784 (78.4%), respectively. The membrane efficiencies measured in this study at s 0 of 172 kPa (25 psi) and 241 kPa (35 psi) were similar to those previously reported for the same GCL using a rigid-wall cell but at unknown states of stress. The practical significance of the results is illustrated in the form of an analysis showing a reduction in liquid flux across the GCL with increasing membrane efficiency.
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consolidation of a geosynthetic Clay Liner under isotropic states of stress
Journal of Geotechnical and Geoenvironmental Engineering, 2010Co-Authors: Jong-beom Kang, Charles D ShackelfordAbstract:The consolidation behavior of a geosynthetic Clay Liner (GCL) was evaluated by consolidating duplicate specimens of the GCL in a flexible-wall cell to a final effective stress, σ′ , of 241 kPa (35.0 psi). The hydraulic conductivity, k , also was measured at the end of each loading increment. The results indicated that the GCL was normally consolidated for values of σ′ greater than 34.5 kPa (5.0 psi), which correlates well with limited consolidation data reported in the literature for GCLs based on confined compression using oedometers. Values of the coefficient of consolidation, cv , for the GCL ranged from 5.2× 10−10 m2 /s to 2.1× 10−9 m2 /s , and generally decreased with increasing σ′ , albeit only slightly. Values of the measured k , kmeasured , for the GCL were low ( ⩽5.0× 10−9 cm/s ) due to the sodium bentonite content of the GCL, and were within a factor of about two of the values of k calculated on the basis of classic (Terzaghi) small-strain consolidation theory, ktheory (i.e., 0.5⩽ ktheory /...
R. Kerry Rowe - One of the best experts on this subject based on the ideXlab platform.
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The 14-year Performance of a Compacted Clay Liner used as Part of a Composite Liner System for a Leachate Lagoon
Geotechnical & Geological Engineering, 2005Co-Authors: Craig B. Lake, R. Kerry RoweAbstract:The migration of contaminants through a 2.9 m thick compacted Clay Liner (CCL) for a landfill leachate lagoon is examined 14 years after construction. The Clay Liner formed the lower portion of the composite Liner system but the geomembrane (GM) was found to have defects that had allowed leachate to migrate between the GM and CCL. Chloride, sodium, potassium, calcium and magnesium pore water profiles through the CCL are examined. It is shown that chloride migrated approximately 1.7 m into the CCL during the 14 years of the lagoon operation, sodium approximately 1.2 m, and potassium 0.7 m. Diffusion and sorption data from laboratory diffusion testing are utilized in combination with a finite layer contaminant transport model to predict field contaminant migration profiles through the composite Liner system and to establish the time of ‘failure’ of the geomembrane at sometime between 0 and 6 years after installation. Relatively high sorptive uptake of potassium by the CCL soil is observed from batch testing and diffusion testing with field data suggesting an even larger amount of sorption. It is hypothesized that organic sludge matter at the base of the lagoon is responsible for potassium uptake from the leachate. This field case highlights the importance of the compacted Clay Liner as part of the composite Liner system in acting as a diffusion barrier during the lifetime of the lagoon as well as using relatively non-conservative contaminants such as chloride and sodium to estimate geomembrane ‘failure’ times
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Investigation of the Behavior of Geosynthetic Clay Liners Subjected to Thermal Gradients in Basal Liner Applications
Journal of ASTM International, 2004Co-Authors: Jonathon M. Southen, R. Kerry RoweAbstract:Composite Liners comprised of geomembranes and geosynthetic Clay Liners can be an effective means of minimizing fluid flow and associated groundwater contamination from municipal solid waste landfills. There remains uncertainty, however, regarding the long-term performance of such systems under conditions of elevated temperature that may occur at the base of landfills attributable to exothermic waste degradation processes. The heat generated by these processes may lead to the development of a thermal gradient through the lining system that creates a risk of desiccation within the uppermost portion of the subsoil and the geosynthetic Clay Liner itself. To investigate this issue, a series of small-scale laboratory experiments were developed in an effort to simulate the hydraulic and thermal conditions existing at the base of a landfill. This paper presents the results of investigations into the influence of various parameters on the behavior of a composite Liner. The distribution of temperature and water content over time is discussed, as well as potential impacts on the performance of the geosynthetic Clay Liner.
Kerry R Rowe - One of the best experts on this subject based on the ideXlab platform.
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hydraulic performance of gcl seams without field applied supplemental bentonite below a geomembrane wrinkle
Journal of Geotechnical and Geoenvironmental Engineering, 2017Co-Authors: Prabee Joshi, R W I Achma, Kerry R RoweAbstract:AbstractThe hydraulic performance of geosynthetic Clay Liner (GCL) overlapped seams relying on hydration of panel bentonite through a melted groove in one of its geotextiles to seal the overlap is ...
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hydraulic performance of overlapped geosynthetic Clay Liner seams requiring field applied supplemental bentonite
Journal of Geotechnical and Geoenvironmental Engineering, 2016Co-Authors: R W I Brachman, Prabeen Joshi, Kerry R RoweAbstract:AbstractThis article investigates the hydraulic performance of geosynthetic Clay Liner (GCL) overlapped seams subjected to nonuniform stresses due to a wrinkle in an overlying geomembrane. The performance when the GCL seam was parallel to and directly below a wrinkle depended on the width of the GCL seam relative to the deformed wrinkle. When both ends of the seam were confined under vertical stress from the deformed wrinkle, there was no evidence of preferential flow along the seam, and the magnitude of flow was slightly smaller than the case with just a single intact GCL panel beneath the wrinkle. Flow through the GCL seam when perpendicular to a wrinkle was mostly affected by the presence and distribution of supplemental bentonite. With no supplemental bentonite, flow was 370 times greater than that through an intact GCL panel beneath the wrinkle. Application of 400 g/m of supplemental bentonite piled along the center of the seam decreased the flow by more than two orders of magnitude compared with ha...
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sorption and diffusion of bisphenol a bpa through a geosynthetic Clay Liner gcl
Geotextiles and Geomembranes, 2016Co-Authors: Pooneh T Saheli, Kerry R RoweAbstract:Abstract Partitioning of bisphenol A (BPA) to geotextile (GTX), and geosynthetic Clay Liner (GCL) is investigated. BPA distribution coefficients range from 3.3 to 5.0 mL/g for the geotextile component of the GCL and 10–16 mL/g for the entire GCL. The diffusion of BPA through the GCL is also investigated and the diffusion coefficient is estimated to be 1.5 × 10 −10 m 2 /s at a bulk void ratio of 4.4. The estimated parameters are used to study the potential mass transfer of BPA through a composite Liner of a municipal solid waste landfill for a number of scenarios. The results show that HDPE geomembrane is an excellent diffusive barrier for BPA but the advective transfer of BPA through the composite Liner needs to be limited by minimizing the number of holes and length of the wrinkles in the geomembrane.
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btex diffusion and sorption for a geosynthetic Clay Liner at two temperatures
Journal of Geotechnical and Geoenvironmental Engineering, 2005Co-Authors: Kerry R Rowe, Toshifumi Mukunoki, Henri P SangamAbstract:The diffusion and sorption characteristics of a geosynthetic Clay Liner (GCL) are examined for a group of volatile aromatic hydrocarbons: benzene, toluene, ethylbenzene, m&p-xylene, and o-xylene (BTEX) at two different temperatures. It is shown that geotextile component of a GCL contributes to the sorption of hydrocarbons by the GCL. While the partitioning coefficients of the BTEX compounds have the order m&p-xylene ≈ethylbenzene>o-xylene>toluene>benzene , the diffusion coefficients have the order benzene>toluene>ethylbenzene>m&p-xylene≈o-xylene . The reduction in diffusion and sorption coefficients with decreasing temperature have opposite effects in terms of the rate of contaminant movement through a GCL. However, it is shown that the decrease in transport due to a reduced diffusion coefficient dominates and mass transport is reduced at lower temperature.
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modeling of Clay Liner desiccation
International Journal of Geomechanics, 2005Co-Authors: Yafei Zhou, Kerry R RoweAbstract:The potential for the desiccation of Clay Liner component of composite Liners due to temperature field generated by breakdown of organic matter in municipal solid waste landfills is examined using a model proposed by Zhou and Rowe. In these analyses, a set of fully coupled governing equations expressed in terms of displacement, capillary pressure, air pressure, and temperature increase are used, and numerical results are solved by using finite element method with a mass-conservative numerical scheme. The model results are shown to be in encouraging agreement with experimental data for a problem involving heating of a landfill Liner. The fully coupled transient fields ~temperature, horizontal stress change, suction head, and volumetric water content! are then examined for two types of composite Liner system, one involving a geomembrane over a compacted Clay Liner ~CCL! and the other involving a geomembrane over a geosynthetic Clay Liner ~GCL!. It is shown that there can be significant water loss and horizontal stress change in both the CCL and GCL Liner even with a temperature increase as small as 20°C. The time to reach steady state decreases as boundary temperature increases. Under a 30°C temperature increase, it takes 5 years to reach the steady state water content with a GCL Liner but 50 years with a CCL Liner. The effects of various parameters, such as hydraulic conductivity and thickness of the Liner, on the performance of the Liner are discussed.
Takeshi Katsumi - One of the best experts on this subject based on the ideXlab platform.
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hydraulic performance and chemical compatibility of a powdered na bentonite geosynthetic Clay Liner permeated with mine drainage
Soils and Foundations, 2019Co-Authors: Angelica Naka, Giancarlo Flores, Toru Inui, Hirofumi Sakanakura, Takeshi KatsumiAbstract:Abstract The hydraulic and chemical compatibility of a geosynthetic Clay Liner (GCL), containing powdered Na-bentonite, was evaluated against artificial acid rock drainage (ARD) in terms of the swell index, hydraulic conductivity and heavy metal retention. Six artificial ARDs with an approximate pH of 3 and different metal concentrations (electrical conductivity, EC, ranging between 75 and 1000 mS/m; ionic strength ranging between 8 and 400 mM) were used in the experiments. The results of free swelling tests showed that high metal concentrations (EC higher than 70 mS/m) negatively impact the swell volume by lowering it. The hydraulic conductivity of the GCL permeated with distilled water was 1.2 × 10−11 m/s, falling in the range of 7.9 × 10−12 to 1.1 × 10−10 m/s when prehydrated with distilled water and permeated with ARDs. The ion exchange and metal precipitation appeared to be the main mechanisms controlling the metal attenuation on the bentonite. The ion exchange mechanism starts with the release of Na from the bentonite and the sorption of the bi- and tri-metals present in the ARDs onto the bentonite. After the depletion of Na, the ion exchange reaction proceeds with the desorption of Ca and Mg from the bentonite and the sorption of cations present in the ARDs onto the bentonite layers. The depletion of Na from the bentonite and the subsequent release of Ca and Mg correlate to the sudden drop in pH and a gradual increase or equilibration of the hydraulic conductivity. It is possible to say that, after this point, hydraulic and chemical equilibrium is reached. From the overall results, the tested GCL showed acceptably low hydraulic conductivity and the potential to attenuate heavy metals present in ARDs.
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effect of acid buffering capacity on the long term mobility of heavy metals in Clay Liner
Soils and Foundations, 2004Co-Authors: Huyuan Zhang, Masashi Kamon, Takeshi KatsumiAbstract:The pH and Eh effects on the mobility of zinc within landfill Clay Liner are investigated by modified batch tests on Osaka marine Clay with cultivation of native microorganisms in the soil. The long-term mobility of zinc in landfill Clay Liner is discussed based on the pH buffering capacity of Liner soil-leachate system. Tests results show that both pH and Eh conditions control the mobility of zinc in Osaka marine Clay. Low redox potentials and neutral to basic pH conditions in landfill sites tend to prompt the insolubilization of zinc in landfill Liner, in particular in the case where marine Clay is used to serve as a natural Liner material at offshore landfill sites. In the long-term perspective, oxygen will intrude finally into the landfill, which switches the anaerobic decomposition into an aerobic one and results a decrease in pH. Titration test results indicate that the newly generated leachate has a higher acid buffering capacity than the aged leachate, while leachates from MSW incineration ash have high hydroxides alkalinity at pH>8. Test results reveal that both of the wastes and Clay Liner possess enough acid buffering capacity to consume the protons produced in organic oxidation reactions. Therefore, high levels of remobilization of heavy metals are not expected in the long-term perspective.
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redox effect on the hydraulic conductivity of Clay Liner
Soils and Foundations, 2002Co-Authors: Masashi Kamon, Huyuan Zhang, Takeshi Katsumi, Naoki SawaAbstract:Microbial activities can be enhanced by organic rich leachate occurring in solid waste landfills, which possesses the potential to alter the barrier capacity of Clay Liners. Flexible-wall hydraulic conductivity tests are conducted to investigate the effect of the microbial activities on the hydraulic conductivity of Osaka marine Clay used for Clay Liners of offshore solid waste landfill sites in Japan. Permeants with different redox potentials are employed to investigate the redox effect; and, permeants with high nutrients are used to check the effect of the microbial production in soil specimens. Test results indicate that there are no obvious changes in the free swell index, the liquid limit, or the hydraulic conductivity of the marine Clay when a strong reducing agent is used. When nutrients are applied for the growth of microorganisms, however, a decrease in hydraulic conductivity, ranging from greater than two orders of magnitude to less than one order of magnitude, is observed. The formation of biofilm and anaerobic inorganic precipitation on the surface of the soil particles is considered to be responsible for this reduction in hydraulic conductivity. Test results reveal that microbial activities, enhanced by landfill leachate, may not cause an increase in the hydraulic conductivity of natural Clay Liners of offshore landfill sites.
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redox effects on heavy metal attenuation in landfill Clay Liner
Soils and Foundations, 2002Co-Authors: Masashi Kamon, Huyuan Zhang, Takeshi KatsumiAbstract:Landfill leachate is characterized by high organic compounds that can be used by microorganisms as nutrients and induce a series of redox reactions. Thus, redox potential as well as pH is considered to have an effect on the behavior of contaminants in leachate from landfill sites. Modified batch tests, cultivating the native microorganisms in soil specimens, were conducted to evaluate the bacteria-induced redox and pH effects on the natural attenuation mechanisms of heavy metal in the bottom Clay Liner of landfills. The marine Clay sampled from Osaka Bay, Japan was used as a natural Clay Liner material due to the consideration that some of the solid waste landfill sites in Japan are located in coastal areas. Iron and zinc were selected as target pollutants. Test results show that both pH and redox potential indicated a combined effect on the solubility of zinc and iron. Under the denitrification and Fe(III) reduction conditions, zinc was soluble and its solubility was only controlled by pH. When pH increased higher than 7.2, zinc precipitated as hydroxides and adsorbed on soil particle surfaces. Under the sulfate reduction condition, the formation of zinc sulfides became another attenuation mechanism. Iron was insoluble under the aerobic and denitrification conditions in natural pH conditions. Elevated levels of soluble iron were observed in moderately reduced and highly reduced conditions. A combination of nearly neutral pH and extremely low redox potential condition in landfill site tends to promote the insolubilization of zinc but the solubilization of iron.
Jialiang Shi - One of the best experts on this subject based on the ideXlab platform.
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shear strength and failure mechanism of needle punched geosynthetic Clay Liner
Geotextiles and Geomembranes, 2020Co-Authors: Shijin Feng, Jiyun Chang, Yang Shen, Hongxin Chen, Jialiang ShiAbstract:Abstract The internal shear strength of a geosynthetic Clay Liner (GCL) within composite Liner systems is crucial for the stability of landfills and should be carefully considered in the design. To explore the shear strength and failure mechanism of the extensively used needle-punched GCL, a series of displacement-controlled direct shear tests with five normal stress levels (250–1000 kPa) and eight displacement rates (1–200 mm/min) were conducted. The shear stress to horizontal displacement relationships exhibit well-defined peak shear strengths and significant post-peak strength reductions. The monitoring results of the thickness change indicate that the degree of volumetric contraction is related to the reorientation of fibers and dissipation of pore water pressure. Furthermore, the peak and residual shear strengths both depend on the displacement rate because of the rate-dependent tensile stiffness of needle-punched fibers and shear strength of the soil/geosynthetic interface. Through additional tests and lateral comparison, it was discovered that the shear behavior of sodium bentonite, degree of hydration, and pore water pressures all affect the shear mechanisms of the NP GCL. In particular, the failure mode transfers from fiber pullout to fiber rupture with the increase in water content as the hydrated bentonite particles facilitate the stretching of needle-punched fibers.
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experimental study of shear strength of geosynthetic Clay Liner for monotonic loading
The International Congress on Environmental Geotechnics, 2018Co-Authors: Jiyun Chang, Shijin Feng, Yang Shen, Hao Shi, Jialiang ShiAbstract:Internal shear strength of geosynthetic Clay Liner (GCL) is of vital importance for the stability of waste containment facilities where GCLs are widely used as hydraulic barriers. This paper presents an experimental investigation of the internal shear strength of hydrated needle-punched geosynthetic Clay Liners (NP GCLs) under monotonic loading. A new dynamic direct shear apparatus with the capability to cover a large range of normal stress and displacement rate is developed. Series of direct shear tests on NP GCL for different normal stress levels and displacement rates are performed. The failure mechanism of hydrated GCL is explored through inspection of tested specimens and analysis of test results. The intrinsic relationship between peak/residual shear strength of NP GCL and displacement rate is also studied. Experimental results indicated that displacement rate has obvious effect on the peak shear strength of NP GCL, while the influence of displacement rate on residual shear strength is of little significance for the same normal stress level.