Compacted Soil Liners Research Articles

Compacted Soil Liners and Covers for Waste Containment

An effective waste disposal system is essential in preventing the infiltration of leachate into the ground and achieving the sustainable development goal of ensuring access to clean and potable water. Liner is an important component of landfill in waste disposal facilities as it impedes the flow of leachate from the landfill. The choice of liner material depends on factors, such as the type and availability of soil, the site conditions, sustainability, and cost-effectiveness. This paper focuses on different soil types as compacted liners in waste containment facilities. The main purpose of this paper is to present the findings of laboratory investigations and measurements of hydraulic conductivity and other important soil properties extracted from previous literature with the aim of providing a guide in material selection for use as compacted soil liners and covers in waste containment applications. The key results of many laboratory studies previously conducted on soils of different properties, gradation, plasticity, and mineralogy, untreated or stabilized with various additives such as waste materials from industries, agricultural by-products and municipal waste materials are reported. The paper also presents the potential of using biopolymer-treated soils (soils modified by polymers) derived from plants and animals, as potential liner materials.

Geotechnical Evaluation of Loess Modifications as the Sustainable Compacted Soil Liner Material in Solid Waste Landfill.

This paper studied the anti-seepage ability of the modified loess by using attapulgite, which is abundant in local areas. The possibility of using the modified loess as the sustainable compacted soil liner material in a solid waste landfill was also considered in this research. The materials were then evaluated using Nuclear Magnetic Resonance (NMR), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and an Impermeability Mechanism (IM). The experimental results showed that the permeability coefficient of the attapulgite-modified loess decreases significantly with increasing attapulgite content. However, it becomes less significant when the attapulgite level approaches 10%. Both cases can meet the landfill impermeability requirements, based on the attapulgite content remaining at 10%, adding 15% lime or 5% cement, respectively. The triaxial consolidation and drainage experiment was carried out to investigate the shear strength of the materials under three different working circumstances. The stress–strain curves of each specimen were produced, as were the cohesion and internal friction angle values. This research lays the groundwork for using attapulgite-modified loess as a landfill lining material. It establishes a solid platform for future studies on attapulgite adsorption and purifying performance in landfills.

Desiccation Induced Shrinkage of Compacted Lateritic Soil Treated via Enzymatic Induced Calcium Carbonate Precipitation Technique

Exploring the biological process to enhance the engineering properties of soil have received enormous recognition in recent years. Enzymatic induced calcium carbonate precipitation (EICP) is one of the bio-inspired methods of utilizing free urease to precipitates calcite from urea and calcium ions for bettering the geotechnical properties of poor soils. In this research, the EICP technique was used to improve the volumetric shrinkage strain of compacted soil liner. In this work, the residual soil was treated with various concentrations of cementations ranging from 0.25 to 1.0 M, and the soil was subjected to Atterberg limit tests, compaction test using British standard light (BSL) and reduced British standard light (RBSL) and desiccation drying volumetric shrinkage strain test. The study's findings revealed a remarkable improvement in the liquid limit and plasticity index of the treated residual soils compared to natural soil. It was also found that the volumetric shrinkage strain of the treated soil reduces progressively from 5.24% of natural to 1.49% at 1.0 M cementation solution when the soils were prepared at 0% OMC and BSL compaction effort. Based on the consideration of permissible VSS of less than 4%, the best treatment was obtained at 1.0 M for both BSL and RBSL prepared samples. Similarly, the best compaction plane is found in the treated with 1.0 M cementation solution.

Analytical solutions for one-dimensional contaminant ion transport through electro-kinetic barriers

To prevent contaminant ions from spreading over the adjacent environment, it is of great interest to consider using electro-kinetic barriers to counteract contaminant transport through the combined effects of electro-osmosis and electro-migration. In this study, considering the bottom surface as a Cauchy boundary or a Drichlet boundary condition, two analytical solutions are proposed to predict the contaminant ion transport in the electro-kinetic barrier. Analytical solutions are verified against experimental data and numerical solutions from the previous literature. Subsequently, the proposed analytical solutions are used to investigate the effects of average applied voltage gradient, barrier thickness, diffusion coefficient, retardation factor and electro-osmotic conductivity on the transport of contaminant through the electro-kinetic barrier. The results show that the steady state base contaminant concentration decreases with the increase in average voltage gradient and barrier thickness. Additionally, the logarithm of the final stable base contaminant concentration changes linearly with the average applied voltage gradient and barrier thickness. For the contaminants with a high diffusion coefficient, a larger average voltage gradient should be applied to improve the electro-kinetic effects. Clayey soils with high sorption capacity and relatively high electro-osmotic conductivity are the suggested material choice for constructing compacted soil liners within the electro-kinetic barrier, due to distinct advantages in contaminant migration prevention. Finally, a dimensionless factor is introduced to uniformly describe influences on the base relative concentration, and it can be used as an important parameter for the design of an electro-kinetic barrier.

Effect of compaction characteristics on hydraulic conductivity performance for sedimentary residual soil mixed bentonite as compacted liners

This paper discusses on the compaction effect to the hydraulic conductivity performance for the sedimentary residual soil mixed bentonite. This mixture is proposed as a barrier material in landfill area and may possibly potential materials for use as compacted soil liners in landfills for leachate protection. A laboratories series was conducted to evaluate the effectiveness of compaction characteristics on sedimentary residual soil mixed with different percentage of bentonite (5%, 10% and 15%). The sedimentary residual soil sample was used in this study and was collected in sedimentary residual formation area in Salak Tinggi, Malaysia and named as Salak Tinggi soil. The mixed samples were compacted at three different compaction effort with different energy to determine the maximum dry density (MDD) and optimum moisture content (OMC). Then, the permeability test to determine the hydraulic conductivity (k) was conducted at MDD condition at every compaction effort at effective stress of 100 kPa. The results show that the MDD value were slightly low for the entire soil sample mixed with bentonite at all compaction energy level. Instead it shows all the three different compaction efforts applied to the mixed soil samples with bentonite yielded hydraulic conductivity less (k ≤ 1x10−9m/s). In fact, the increment of bentonite content also resulted in lower of MDD value and hydraulic conductivity value. However, MDD values were found to be higher for mixed soil when compacted with high compaction effort. The results of hydraulic conductivity tests demonstrated that hydraulic conductivity, k ≤ 1x10−9m/s can be achieved just by using lower compaction energy for the soil mix with bentonite. Instead it considered as suitable materials for liner due to the hydraulic requirement for soil barrier, k ≤ 1x10−9m/s. This finding show that compaction efforts play an important role for workability of the mixtures and significantly to be used as compacted of soil liner materials.

Evaluation of the Hydraulic Conductivity of Compacted Laterite-Metakaolin Mixtures for Solid Waste Leachate Containment

This paper presents the results of a study conducted to investigate the benefits of using metakaolin (MK) with laterite as liner material for containment of municipal solid waste (MSW). Laboratory tests were conducted on laterite specimens treated with MK at concentrations of 0 - 20 % by weight of the soil and compacted using four types of compaction energies. Hydraulic conductivity was determined based on permeation of the compacted laterite - MK mixtures with deionized water (DW) and municipal solid waste leachate (MSWL), respectively. Deionized water was the reference permeant fluid. The results showed that hydraulic conductivity generally decreased with increase in the percentage addition of MK to the soil. From an economic and sustainability point of view, it has been found from the results that 5 % MK can be added to soil and compacted at moulding water content of 14.1 % using the West African Standard (WAS) compaction energy to achieve the regulatory hydraulic conductivity of less than or equal to 1 x 10-9 m/s for compacted soil liner. The natural logarithm of the hydraulic conductivity experimental results were computed and used to develop regression equations for estimating hydraulic conductivity given MK contents and compaction energies. The results of the two-way analysis of variance (ANOVA) test carried out at 5 % level of significance showed that calculated F-statistics are statistically significant and the measured values of hydraulic conductivity compare well with the predicted values. The developed models can therefore be used to give good estimates of hydraulic conductivity of soils having similar properties with the laterite investigated in this study. Therefore, the developed models can be used to give good estimates of hydraulic conductivity of soils having similar properties with the laterite investigated in this study. Keywords ­_ Deionized water, Hydraulic conductivity, Leachate, Metakaolin, Municipal solid waste.

Numerical modeling of leachate migration in compacted tropical laterite soil

To protect groundwater from leachate contamination in sanitary landfill involve the use of hydraulic barriers i.e. liners and covers. Nonetheless, can these barriers continue to impede the migration of leachate over a long period? A full-scale experiment would be prohibitively costly and time consuming. The only feasible recourse therefore is to construct a model, which reasonably portray the behaviour of the full-scale system and simulate the relevant physical parameters and describes the overall significant characteristics of the transport phenomena. This research investigates the long-term performance of compacted tropical laterite soil liners at various gradations against leachate migration in sanitary landfills using numerical modeling. Series of laboratory experimentation were carried out using three different laterite soil gradations (30%, 40% and 50% with respect to fines content) compacted at optimum moisture content using British Standard light energy. Leachate was poured on the compacted soil in an acrylic column and its migration was monitored using Digital Image Technique (DIT). Subsequently, PetraSim computer software a graphical interface used to solve problems related to contaminant transport was applied to predict the velocity of leachate migration. The predicted velocity values for 30%, 40% and 50% fines are 4.5 x 10−7 m/s, 7 x 10−9 m/s, and 8 x 10−10 m/s, respectively. This shows that the laterite soil with 50% fines content is more compatible with the leachate and can be used as soil liner. The outcome of this research would enable designers to use non-destructive method to monitor and predict leachate migration in compacted soil liners to simulate leachate migration in waste containment applications.

A critical reappraisal of residual soils as compacted soil liners

Compacted residual soils are often used as liner materials in engineered landfills, tailings dams, solar ponds, and canals, etc. to minimize the migration of contaminants into the surrounding environment and groundwater. To date, there has not been an extensive and adequate review of the suitability of different residual soil types for use as compacted liner materials. This paper reviews the suitability, merits, demerits, and possible applications of using expansive and lateritic residual soils as compacted soil liners. The review is then complemented by a study of the geotechnical properties of lateritic residual and shrinkable soils from Peninsular Malaysia. Suitability was assessed based on engineering property data for both soil types, collected from various journal papers, workshops, proceedings of conferences, and symposia from around the world. These properties were then compared with the standard requirements for use as liner materials. Descriptive statistics were employed to better assess the individual criteria of using both residual soil types as compacted soil liners. The results indicate that expansive and lateritic soils can be effectively utilized as liner materials if more acceptable materials are not readily available. The study addresses untreated soils but does not discuss the stabilization aspects.

A Review on the Effects of Gradation on Shear Strength Characteristics of Compacted Laterite Soil Liner

A Review on the Effects of Gradation on Shear Strength Characteristics of Compacted Laterite Soil Liner

HYDRAULIC CONDUCTIVITY AND VOLUMETRIC SHRINKAGE PROPERTIES REVIEW ON GRADATION EFFECT OF COMPACTED LATERITE SOIL LINER

This paper reviews the effects of gradation on hydraulic conductivity and volumetric shrinkage properties of compacted laterite soil liner. The distribution of different grain sizes affects the engineering properties of soil such as compressibility, swelling and shrinkage, shear strength, and hydraulic conductivity. It is observed that there are dissimilarities of values in laterite soils from various researches around tropical countries of the world in terms of hydraulic conductivity and volumetric shrinkage. Hydraulic conductivity varies from 4.36×10-3 m/s to 4.7×10-11 m/s and volumetric shrinkage of ≤ 4%relative to fine contents ranging from 1.3% to 69% and coarse contents ranging from 31% to 98.7%.Generally, there is no clear trend established for effects of gradation on hydraulic conductivity and volumetric shrinkage properties of compacted laterite soil liners. This is because laterite soils with less than 50% fines content might not be used as liner or hydraulic barriers because their hydraulic conductivities are less than the minimum requirement of 1 × 10-9 m/s. At times researchers usually left out volumetric shrinkage in their study, but field studies have shown that desiccation can induce severe cracking of unprotected soil barriers. When fine grained soils lose moisture they tend to shrink, which result to cracking that can adversely affect the engineering properties and performance of the soils. The adversative influence includes reduced strength of the cracked soils and increased hydraulic conductivity. It is expected that with logical understanding of the effects of gradation on hydraulic conductivity and volumetric shrinkage properties of compacted laterite soil it will serve as a guide in the design of hydraulic barriers for engineered sanitary landfills in tropical countries around the world.

STUDY OF WATER FLOW AND RETENTION IN CLAY-SAND LINERS

This research paper presents a simulation study to predict the percolation of water through soilliners using numerical modeling with HYDRUS-2D. The soil liners included compacted clay/sand mixturesof 0 to 25% clay at 5 to 30 cm thickness. The cumulative water flux or hydraulic barrier at drain layer at theend of simulation period reached a ratio of 0.81, 0.54, 0.29 and 0.09 of water flux at a top profile with no soilliner. The soil liners of 25 and 30 cm thickness with 20% and 15% clay had lesser percolation or water fluxat drain layer by about 0.21 and 0.44 compared to water flux at top layer with no soil liner. Using a modelingapproach efficient liner systems can be designed for use in water harvesting projects or landfill covers. Themodeling and simulation are dependent on the hydraulic conductivity of the compacted soil liner, soil watercharacteristics curves as well as irrigation and rainfall rates.

Hydraulic Conductivity of Compacted Soil Liners Permeated with Coal Combustion Product Leachates

AbstractTests were conducted on eight soils to determine how coal combustion product (CCP) leachates may affect the hydraulic conductivity of compacted soil liners (CSLs) used for CCP disposal faci...

Computer Modeling Approach of Leachate Flow in Compacted Laterite Soil Liner

The use of hydraulic barriers in sanitary landfills has become an impeccable means of protecting the groundwater system from leachate. A question to be asked is, can these barriers continue to impede the migration of leachate over a long period? This paper investigates the phenomenon of leachate migration in compacted laterite soil used as liner in sanitary landfills. An experiment was carried out using laterite soil compacted at optimum moisture content using Standard Proctor energy. Leachate was poured on the compacted soil in an acrylic column and its migration was monitored using Digital Image Technique (DIT). The DIT capture photographic images at successive intervals of time which were fed through an image processing code to convert them to hue-saturation-intensity (HSI) format with the help of Surfer and Matlab computer softwares. Subsequently, PetraSim computer software was applied to predict the velocity behavior. The predicted velocity value shows that the laterite soil is compatible with the leachate and can be used as soil liner. The outcome of this study would enable designers to use non-destructive method to monitor and predict leachate migration in compacted soil liners to simulates leachate migration in waste containment applications.

Geotechnical properties of a natural zeolite

An investigation into the geotechnical properties of a natural, crushed and ground zeolite used as a compacted soil liner in geoenvironmental applications was carried out to ensure adequate strength and permissible compressibility. Tests aimed at examining the influence of gradation, density and stress level on strength show that the zeolite behaves as any granular material with its shear strength in direct shear increasing with density and stress level and decreasing with increasing uniformity. To validate these findings direct shear tests were performed on two quartz sands of similar mean diameter and varying gradations and grain shape. The results of the tests on the zeolite and the sand of similar gradation and grain shape nearly coincide. For the zeolite under consideration, which is mainly composed of clinoptilolite, grain crushing is negligible for stress levels common in engineering construction. Finally, the influence of wetting on the shear strength of the zeolite is insignificant. The results indicate that these materials can be analysed within the framework of behaviour for quartz sands.

Breakthrough time-based design of landfill composite liners

Breakthrough time based design methods for determining the design thickness of landfill composite liners are proposed. The composite liners consist of either 1) a geomembrane (GMB) and a compacted clay liner (CCL), 2) a geomembrane (GMB), a geosynthetic clay liner (GCL) and a soil liner (SL), or 3) a GCL and a SL. The design methods are based on analytical solutions developed for solute advection and dispersion of leachate contaminants in composite liners. Both solute concentration and solute flux are considered in the analyses. Two dimensionless parameters involving contaminant concentration and contaminant flux are introduced and the design curves are proposed for breakthrough time based design of composite liners. The results obtained by the proposed analytical solutions are in good agreement with the experimental data published in the literature. Illustrative examples are presented to demonstrate the application of the design methods for composite liners consisting of a GMB and a compacted soil liner and those consisting of a GMB, a GCL, and a SL. The effect of leachate head on the design thickness of composite liners was investigated. It is shown that the design methods presented in this paper is easy to be used to design the landfill composite liners in different leachate head cases.

Hydraulic conductivity of compacted soils controlled by microbial activity

The hydraulic conductivity defines the displacement of liquids inside porous media and affects the fate and transport of contaminants in the environment. In this research the influence of microbial growth and decay inside soil pores on hydraulic conductivity is analysed. Long-term tests performed in silt–bentonite mixtures permeated with distilled water and a nutrients solution demonstrated that hydraulic conductivity of compacted silt–bentonite samples decreases with time of permeation as a bioclogging mechanism develops. The injection of antibiotics and antifungals in the specimens produces a rebound in the hydraulic conductivity associated with the decay of microbial activity. These results show that biomediated reactions can be used to control the flow rate through compacted soil liners.

Improvement of Barrier Soil Properties with Fly Ash to Minimize Desiccation Shrinkage

Barrier Systems Built with Fine Grained Soils Frequently Loose their Hydraulic Integrity due to Desiccation Cracking either during Construction or Shortly Thereafter. Moreover, Typical Specifications for the Construction of Compacted Soil Liners and Covers Require that the Soil Be Compacted Wet of Optimum Water Contents to Achieve the Lowest Possible Hydraulic Conductivity, a Condition that Results in High Desiccation Shrinkage Values. however, such Soils Can Be Treated with Fly Ash to Maintain Low and Tolerable Desiccation Shrinkage Strains. in this Study, Volumetric Shrinkage Strains of Representative Fine Grained Soil Containing 0 – 20% Fly Ash by Dry Weight of Soil Compacted with the British Standard Light (BSL), West African Standard (WAS) and British Standard Heavy, (BSH) Compaction Efforts at Moisture Contents Ranging from 10 – 20% Were Evaluated. Measurements Indicate that Volumetric Shrinkage Strain Decreased with Higher Fly Ash Content and that Fly Ash Effectively Reduced the Shrinkage of Untreated Soil Prepared Wet of Optimum from 4.4 – 7.7% to Values Well below the 4% Threshold. the Measured Shrinkage Strains Were Related to Water Content and Dry Unit Weight on the Dry Unit Weight – Moulding Water Content Curve in what Is Referred to as Acceptable Zone. Data Points within the Acceptable Zone Represent Test Results with Shrinkage Strain ≤ 4% which Ensures Compaction Efficiency. this Study Therefore Established that Fly Ash Application and Appropriate Regulation of the Moulding Water Content Are Feasible Means of Reducing the Risk of Barrier Soil Damage by Shrinkage Cracks while still Realizing Very Low Hydraulic Conductivity and Adequate Strength.

Delineation of compaction criteria for acceptable hydraulic conductivity of lateritic soil-bentonite mixtures designed as landfill liners

In current geoenvironmental practice, design engineers usually require that soil liners in waste landfills be compacted within a specified range of water content and dry unit weight. This specification is based primarily on the need to achieve a minimum dry unit weight for factors controlling the performance of compacted soil liners most especially the hydraulic conductivity, k. In this study, lateritic soil treated with up to 10% bentonite, prepared at various compaction states (dry of optimum, optimum and wet of optimum moisture content) was compacted with four compactive efforts (i.e., the reduced British Standard Light, British Standard Light, West African Standard, and British Standard Heavy) to simulate the range of compaction energies expected in the field. Prepared soil mixtures were permeated with water and specimens that yielded the permissible limit of k ≤ 1 × 10−9 m/s were enclosed in an envelope (known as the acceptable zone) on the water content–dry unit weight curve. It was observed that compaction conditions resulting in moisture content slightly wet of optimum led to the lowest values of k and that the shapes and boundaries of the acceptable zones gradually increased in extent, shifting to wet side of optimum moisture content as the bentonite content increased to 10%. This approach provides good control over the quality of compacted soils and has great potential for field application.

Compacted Soil Liner Interface Strength Importance

This paper describes an interesting slope failure in a liner system of a municipal solid waste containment facility during construction because the sliding interface is not the geomembrane (GM)/compacted low-permeability soil liner (LPSL) but a soil–soil interface within the LPSL. Some of the lessons learned are as follows: (1) compaction of the LPSL should ensure that each lift is kneaded into the lower lift so a weak interface is not created in the LPSL; (2) the LPSL moisture content should be controlled so it does not exceed the specified value, for example 3–4% wet of optimum, because it can lead to a weak interface in the LPSL; (3) drainage material should be placed over the GM from the slope toe to the top to reduce the shear stresses applied to the weakest interface; and (4) equipment should not move laterally across the slope if it is unsupported but up the slope while placing the cover soil from bottom to top.

Study on the Hydraulic Conductivity of Sand-Bentonite mixtures used as Liner System of Waste Landfill

A liner system such as liner sheet underlying impermeable soil layer having hydraulic conductivity less than 1*10-7 cm/s and a thickness larger than 100 cm is often used in china. As there is very little natural clay having such low permeability, bentonite is usually mixed into sand to decrease the permeability. In this paper, the compaction tests and permeability testing using flexible-wall permeameter are conducted. The test results show that the value of critical benonite ratio depends on bentonite ratio, and the hydraulic conductivity of the sand mixed with critical bentonite ratio for distilled water shows of the order of 1*10-8 cm/s that satisfies the china standard requested as compacted soil liner of waste landfill. Finally, the permeability testing used leachate including calcium component was conducted.