Hydraulic Conductivity Of Clay Liners Research Articles

Effects of 1,4-dioxane and bisphenol A on the hydraulic barrier performance of clay bottom liners for waste containment facilities

The bentonite and ocean-floor clay used in hydraulic barriers for on-land and ocean waste disposal sites, respectively, act as the last defense against environmental pollution, and therefore must have high chemical resistivity and long-term stability. The primary factors that determine the hydraulic conductivity of bentonite and ocean-floor clay are the polarity and functional groups of their organic compounds as well as their concentration and hydration characteristics in solution. However, it is not known which of the organic compounds reduce the hydraulic barrier performance of clay liners, and the extent of degradation has not been quantified. Recently, high concentrations of 1,4-dioxane and bisphenol A have been detected in some waste leachates. Although these low-polarity compounds hinder the hydration reaction of clay minerals and increase the hydraulic conductivity of clay liners, the magnitude of their impact in the limited concentrations found in leachates remains unclear. In this study, long-term hydraulic conductivity tests are conducted on a bentonite liner and ocean-floor clay samples, where the permeation liquid contains 1,4-dioxane or bisphenol A. The hydraulic barrier performance is evaluated based on the hydraulic conductivity and the distribution coefficient.

Studies on Hydraulic Conductivity of Fly Ash-Stabilised Expansive Clay Liners

Earthen barriers or clay liners are a major concern in geo-environmental engineering. They are designed to preclude or reduce leachate migration. Hence, a low hydraulic conductivity (k) is an important parameter in the design of clay liners. Materials such as bentonite and lateritic clays, which have a low hydraulic conductivity at high dry densities, are used in the construction of clay liners. Compacted expansive clays which are high in montmorillonite content also have a very low hydraulic conductivity. When expansive clays are blended with fly ash, an industrial waste, the hydraulic conductivity further reduces as the ash-clay blends result in increased dry densities at increased fly ash contents. Hence, fly ash-stabilised expansive clay can also be proposed as an innovative clay liner material. It is, therefore, required to study various physical and engineering properties of this new clay liner material. Liquid limit (LL) and free swell index (FSI) are important index properties to be studied in the case of this clay liner material. The hydraulic conductivity of this new clay liner material depends on the fly ash content in the blend. Further, parameters such as solute concentration and kinematic viscosity also influence hydraulic conductivity of clay liners. This paper presents experimental results obtained on hydraulic conductivity (k) of fly ash-stabilised expansive clay liner at varying fly ash content and solute concentration. The tests were performed with deionised water (DIW), CaCl2, NaCl and KCl as permeating fluids. Fly ash content in the blend was varied as 0, 10, 20 and 30 % by weight of the expansive clay, and the solute concentration was varied as 5 mM (milli molar), 10, 20, 50, 100 and 500. It was found that hydraulic conductivity (k) decreased with increasing fly ash content, solute concentration and kinematic viscosity. Further, hydraulic conductivity (k) was correlated with LL and FSI of the clay liner material for different fly ash contents and solute concentrations. Useful correlations were obtained.

Prediction of Field Hydraulic Conductivity of Clay Liners Using an Artificial Neural Network and Support Vector Machine

AbstractThis paper describes the application of artificial neural network (ANN) and support vector machine (SVM) methods for prediction of field hydraulic conductivity of clay liners based on in situ test results such as compaction characteristics, lift thickness, number of lift, and soil classification tests like Atterberg’s limits and grain size. Statistical performances criteria, root mean square error, correlation coefficient, coefficient of determination, and overfitting ratio are used to compare different ANN and SVM models. Different algorithms are discussed for identification of important soil parameters affecting the hydraulic conductivity of clay liners. A model equation based on the parameters obtained using SVM is also discussed.

Swelling Pressure of Compacted Clay Liners Contaminated with Inorganic Salt Solutions

Research Article| November 01, 2010 Swelling Pressure of Compacted Clay Liners Contaminated with Inorganic Salt Solutions SERACETTIN ARASAN; SERACETTIN ARASAN 1Department of Civil Engineering, Ataturk University, 25240 Erzurum, Turkey Search for other works by this author on: GSW Google Scholar R. KAGAN AKBULUT; R. KAGAN AKBULUT 2Vocational School of Higher Education, Ataturk University, Oltu, Erzurum, Turkey Search for other works by this author on: GSW Google Scholar TEMEL YETIMOGLU; TEMEL YETIMOGLU 3Department of Civil Engineering, Ataturk University, 25240 Erzurum, Turkey Search for other works by this author on: GSW Google Scholar GONCA YILMAZ GONCA YILMAZ 3Department of Civil Engineering, Ataturk University, 25240 Erzurum, Turkey Search for other works by this author on: GSW Google Scholar Author and Article Information SERACETTIN ARASAN 1Department of Civil Engineering, Ataturk University, 25240 Erzurum, Turkey R. KAGAN AKBULUT 2Vocational School of Higher Education, Ataturk University, Oltu, Erzurum, Turkey TEMEL YETIMOGLU 3Department of Civil Engineering, Ataturk University, 25240 Erzurum, Turkey GONCA YILMAZ 3Department of Civil Engineering, Ataturk University, 25240 Erzurum, Turkey Publisher: Association of Environmental & Engineering Geologists First Online: 02 Mar 2017 Online ISSN: 1558-9161 Print ISSN: 1078-7275 Copyright © 2010 EEGS Environmental & Engineering Geoscience (2010) 16 (4): 401–409. https://doi.org/10.2113/gseegeosci.16.4.401 Article history First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation SERACETTIN ARASAN, R. KAGAN AKBULUT, TEMEL YETIMOGLU, GONCA YILMAZ; Swelling Pressure of Compacted Clay Liners Contaminated with Inorganic Salt Solutions. Environmental & Engineering Geoscience 2010;; 16 (4): 401–409. doi: https://doi.org/10.2113/gseegeosci.16.4.401 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEnvironmental & Engineering Geoscience Search Advanced Search Abstract Processed and natural clays are widely used to create impermeable liners in solid waste disposal landfills. Swelling pressure and hydraulic conductivity of clay liners can be significantly affected by the leachate from the waste mass. In this study, the effect of five different inorganic salt solutions on the swelling pressure of compacted clay liners was experimentally investigated. As contamination liquids, sodium chloride (NaCl), ammonium chloride (NH4Cl), potassium chloride (KCl), calcium dichloride (CaCl2), and iron trichloride (FeCl3) inorganic salt solutions were used at concentrations of 0.01, 0.10, 0.25, 0.50, 0.75, and 1 M. The swelling pressure tests were conducted after permeation of salt solutions was completed on low-plasticity (CL class) and high-plasticity (CH class) compacted clays. The experimental test results indicated that the effect of inorganic salt solutions on CL (chlorite-smectite) clay samples was different from that on CH (smectite) clay samples. The swelling pressures were found to increase when the salt concentrations increased for contaminated CL clay samples. On the other hand, with increasing salt concentrations, the swelling pressures decreased for the contaminated CH clay samples. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

A linear graphical method to predict the effect of compaction on the hydraulic conductivity of clay liners and covers

It is proposed to present compaction relationships by plotting the inverse of the dry density versus the molding water content. In the proposed graph, the curves for equal degree of saturation become straight lines. The proposed new graph is shown to be very convenient to assess the saturated hydraulic conductivity, k sat, of non-swelling compacted clay, using a dual porosity model. The value of k sat depends on the secondary porosity between clay clods. The equation developed for equal k sat value appears also as a straight line in the proposed graph. It facilitates the prediction of k sat from field compaction data and thus the prediction of field performance of clay liners and covers.

Heterogeneity detection in an experimental clay liner

In situ hydraulic tests to characterize the field hydraulic conductivity of clay liners used in landfill applications are often positioned randomly. Yet it is well known that the field performance of low permeability clay liners is generally controlled by heterogeneities that may provide preferential pathways for flow. In this paper, an experimental clay liner is investigated in which heterogeneities were incorporated in a controlled fashion. Heterogeneities were embedded within a compacted clay liner at different locations in the plane and at different depths. Heterogeneities of composition were installed by excavating compacted clay at specific locations and replacing it with a more permeable material. Heterogeneities of compaction were introduced by loosely backfilling the clay into the excavations. Two geophysical methods, ground penetrating radar (GPR) and the EM-38 electromagnetic method, were used to examine whether anomalies detected by geophysics were or were not correlated with the precise locations of the heterogeneities. Hydraulic tests were used to characterize the permeability of the intact clay on the one hand and of the heterogeneities on the other hand. Three different in situ hydraulic test methods were used: a pulse test performed in a hand-augered borehole, a sealed single ring infiltrometer test, and a large scale infiltration test (4 m2) that uses a color tracer to detect possible preferential flowpaths. The GPR showed no significant correlation with heterogeneity locations, nor did the EM-38 method when used in the vertical dipole mode. The EM-38 method used in the horizontal dipole mode, showed significant correlation with heterogeneities when they were apparent at the surface. On the other hand, the method did not clearly detect heterogeneities located at depth. There was consistency between the values of hydraulic conductivity obtained from the different hydraulic field and laboratory tests. "Intact" clay hydraulic conductivities were found to lie between 10–10 and 4 × 10–9 m/s, while the hydraulic conductivity of the heterogeneities of composition was approximately 10–7 m/s. The results of this experiment suggest that the EM-38 method may be useful to optimize hydraulic test locations when characterizing clay liners for landfill applications.Key words: clay liner, hydraulic conductivity, heterogeneity.

Redox Effect on the Hydraulic Conductivity of Clay Liner

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.

Modeling Soil Correlations Using Neural Networks

In geotechnical engineering, empirical relationships are often used to estimate certain engineering properties of soils. Using data from extensive laboratory or field testing, these correlations are usually derived with the aid of statistical (regression) methods. This paper demonstrates the use of back-propagation neural networks to capture multivariate nonlinear interactions between various soil parameters in a system. Two examples are presented to demonstrate the potential of this approach. The first example involves the analysis of data obtained from calibration chamber tests on sand. The other example relates to the determination of the hydraulic conductivity of clay liners. Actual laboratory test data were used in training the neural network. The performance of the neural-network and multiple-regression models were assessed by evaluating the scatter between the predicted and measured values, via the coefficient of regression and the average sum squared error. The neural-network models were found to be more reliable than the multiple-regression models.

Statistical analyses of compacted clay landfill liners. Part 1: model development

The acceptance of compacted clay liners, from a management point of view, has been a source of major concern because of the uncertainty associated with the hydrogeologic properties of the clay. By examining the flux of leachate through the compacted clay liner of a typical engineered landfill, where the hydraulic conductivity of the clay is represented by a stochastic process, an acceptance protocol suitable for compacted clay landfill liners is derived. Determination of the equivalent hydraulic conductivity of the clay liner is accomplished by comparing the flux of leachate through a homogeneous representation of the clay with the flux obtained by Monte Carlo analyses. Acceptance criteria are subsequently developed based on a statistical technique which calculates the confidence limits about a percentile of a probability distribution as well as about the mean of the distribution. For the landfill configuration simulated, the results indicate that the hydraulic conductivity of a compacted clay landfill liner follows a lognormal distribution and exhibits virtually no spatial correlation structure. In addition, for liners exhibiting a geometric mean conductivity of 10−7 cm/s and a standard deviation of 0.3, the geometric mean value is a conservative estimate of the hydraulic conductivity of the clay, provided the liner is constructed in a series of four 150 mm lifts. Key words: clay liners, hydraulic conductivity, statistical analyses, latin hypercube, equivalent hydraulic conductivity.

Effect of Clod Size on Hydraulic Conductivity of Compacted Clay

Abstract A study has been conducted to identify the causes for field-measured values of hydraulic conductivity of clay liners being typically two orders of magnitude greater than laboratory-measured values. It has been found through laboratory testing on large specimens that the size and gradation of clods and clumps of clay, prior to compaction, can significantly affect the measured hydraulic conductivity. The results of this study are compared to existing studies on the effect of clods on hydraulic conductivity, and general agreement is found. It is concluded that, for clod sizes and gradations likely to occur in field compaction of clay liners, that differences in clod gradation and size between lab and field conditions can essentially account for the observed roughly two orders of magnitude discrepancy between lab and field-measured conductivities. Revised laboratory testing procedures for both the before-liner construction and after-liner construction cases are recommended. The revised laboratory testing procedures are designed to correct the deficiencies in conventional lab testing and to produce unbiased estimates of field hydraulic conductivity values.

Hydraulic Conductivity of Three Landfill Clay Liners

Clay liners have been used as a means of leachate containment at landfills in Wisconsin for over 10 years. Many of these liners are 1.22–1.52‐m (4–5‐ft) thick and their construction is well documented. Since 1980, the Wisconsin Department of Natural Resources has required “collection basin lysimeters” to be installed at most clay‐lined sites to measure the quality and quantity of leakage from a discrete portion of the liner. These devices were initially required to provide a method for monitoring soil moisture in the unsaturated zone beneath the clay liners because in most cases suction lysimeters had not functioned properly. More recently, volume measurements from regularly sampled lysimeters have been used to estimate field hydraulic conductivity of clay liners. Field hydraulic conductivities calculated from the measured rate of seepage into eight separate lysimeters at three operating landfills is always less than 1×10-7cm/s.

Discussion of “ Predicting Hydraulic Conductivity of Clay Liners ” by David E. Daniel (February, 1984)

Discussion of “ <i>Predicting Hydraulic Conductivity of Clay Liners</i> ” by David E. Daniel (February, 1984)

Closure to “ Predicting Hydraulic Conductivity of Clay Liners ” by David E. Daniel (February, 1984)

Closure to “ <i>Predicting Hydraulic Conductivity of Clay Liners</i> ” by David E. Daniel (February, 1984)

Discussion of “ Predicting Hydraulic Conductivity of Clay Liners ” by David E. Daniel (February, 1984)

Discussion of “ <i>Predicting Hydraulic Conductivity of Clay Liners</i> ” by David E. Daniel (February, 1984)

Discussion of “ Predicting Hydraulic Conductivity of Clay Liners ” by David E. Daniel (February, 1984)

Discussion of “ <i>Predicting Hydraulic Conductivity of Clay Liners</i> ” by David E. Daniel (February, 1984)

Discussion of “ Predicting Hydraulic Conductivity of Clay Liners ” by David E. Daniel (February, 1984)

Discussion of “ <i>Predicting Hydraulic Conductivity of Clay Liners</i> ” by David E. Daniel (February, 1984)

Predicting hydraulic conductivity of clay liners : Daniel, D E J Geotech Engng Div ASCEV110, NGT2, Feb 1984, P285–300

Predicting hydraulic conductivity of clay liners : Daniel, D E J Geotech Engng Div ASCEV110, NGT2, Feb 1984, P285–300

Predicting Hydraulic Conductivity of Clay Liners

Data are presented from four projects in which rates of leakage from ponds lined with clay significantly exceeded the rates that would have been predicted on the basis of laboratory permeability tests. The actual hydraulic conductivities of the clay liners were generally found to be 10 to 1,000 times larger than values obtained from laboratory tests on either undisturbed or recompacted samples of the clay liner. The source of difficulty with laboratory permeability tests is the problem of obtaining a representative sample of soil for testing. Neither recompacted samples nor small, undisturbed samples are likely to contain a representative distribution of desiccation cracks, fissures, slickensides, or other hydraulic defects that may be present in the liner. Field permeability tests were performed for three of the four case histories and yielded results that compared well with field performance. Field permeability tests seem to produce much better results than laboratory tests. The four projects had certain features in common: (1) In all cases involving comparatively high rates of leakage, the liners were relatively thin (less than 24 in. or 0.6 m thick); (2) with only one exception, all of the liners were subjected to some desiccation; and (3) in essentially all cases, the construction inspection was not as extensive as it might have been.