Geosynthetic Liners Research Articles

Approach to tailings facility liner configuration selection: A case study

What liner configuration should you use for a tailings facility? Do you need a geosynthetic liner? Should you include overdrains above your liner? This paper presents an approach to answer these questions for a case study tailings facility in a semi-arid environment. The case study project includes a performance criterion that the seepage flux be limited below the impoundment. Four liner configurations were shortlisted, and the efficacy of each arrangement compared with numerical modelling. The configurations are: (1) tailings directly over a liner, (2) tailings on an overdrain system over a liner, (3) tailings on an overdrain system over a blinding layer over a liner, and (4) sealing the foundation with tailings slimes (i.e., no geosynthetic membrane). This paper also presents estimates of the longevity of an HDPE liner system, as this is vital in assessing performance over very long time periods. Seepage and consolidation modelling results indicate that overdrains do not improve the potential to meet the performance criterion and overdrains have a limited post-closure consolidation benefit. All configurations with geosynthetics indicated the liner system would function adequately during the period prior to geosynthetic membrane degradation. The slimes sealing case was shown to not provide an adequate impedance to flow.

Analytical and numerical models for strain and load calculations for geosynthetic liner systems on steep slopes

The paper develops an analytical model based on the force equilibrium for the design of steep slope geosynthetic liner systems to overcome downdrag loads from waste settlement. This analytical model calculates the required tensile stiffness for a high strength/stiffness geotextile (HS-GTX) reinforcement over the GMB to limit the maximum HS-GTX tensile strain to 5% and the maximum GMB strain to 4% on the side slope. The numerical model illustrates the need for reducing the GMB tensile strains for a single GMB liner on a steep landfill slope and confirms that the use of a HS-GTX over the GMB is able to limit the maximum HS-GTX and GMB tensile strains to the acceptable strain levels. The analytical model developed in this paper is a practical tool for preliminary design to limit tensile strains of the HS-GTX and GMB in a steep slope geosynthetic liner system.

Use of Geosynthetic in Soft Soil Foundation in Mining Area: A Case Study with Analytical and Numerical Studies

The design of embankments on soft foundations with the application of geosynthetics is a subject frequently studied. In addition, the disposal of mine waste material is a needed challenge, due to area availability. In this context, this work presents a study case of application of geosynthetics for soft foundations treatment, to make feasible the construction of a mine waste pile embankment. The study also presents a stress–strain analysis via finite-element modeling considering a critical state soil mechanics approach. Then, a geosynthetic liner and internal drainage system design is presented based on the results of this analysis. Hence, this liner and internal drainage are required due to the environmental concerns of the waste material. Thus, a discussion on the use of critical state soil mechanics and the stress–strain finite-element method to assess the need for treatment on foundation for embankments construction in soft material is presented. The deformations assessed at the stress–strain study showed that the waste material would absorb the foundation strains with only controlling the rising ratio. Thus, the solution proposed with the numerical analysis reduces the reinforcement that would be proposed usually. Furthermore, the ease installation process and the large strains capabilities made possible an embankment construction on soft soil near to a mine industrial plant.

Geosynthetic liner: A modern solution for a concrete dam constructed from particularly lean roller-compacted concrete

This paper discusses the issue of seepage control in gravity dams made of compacted lean concrete. Several possible design options are outlined. The benefits of using geocomposite impervious blankets are explained. A description of different types of geocomposites is given, including their composition and component parameters. Basic properties of geosynthetics are discussed, along with methods for defining them, such as water permeability, tensile strength, puncture resistance, and ageing. Finally, the main areas for future research are formulated, although it may be helpful to provide more detail on the specific focus of this research.

Mechanical and Chemical Behaviour of Water Treatment Sludge and Soft Soil Mixtures for Liner Production

Background: Clay-based and geosynthetic liners are generally used as hydraulic barriers in solid waste disposal facilities, mining tailing ponds, and soil-based wastewater treatment technologies, avoiding the leaching of hazardous compounds into subsoil and groundwater. Water treatment sludge (WTS) is a water treatment plant (WTP) residue which due to hydraulic properties seems to decrease the permeability in WTS:soil mixtures and may become an alternative material to produce sustainable waste-based liners. Objectives: This research aims to characterize and analyse physical, chemical and mechanical parameters of a WTS, a soft soil and four mixtures WTS:soil following 05:95%, 10:90%, 15:85%, 20:80% ratios, Thereby, evaluating the best ratio for producing waste-based liners for civil engineering applications. Methods: The geotechnical characterization was performed for particle size distribution, specific surface, specific gravity, Atterberg limits, and Normal Proctor compaction; chemical composition due to oxides analyses through X-ray fluorescence (XRF), mineralogical description by X-ray diffraction (XRD) and scanning electron microscope (SEM) with energy dispersive spectrometer (EDS) coupled for imaging; and mechanical behavior performing - –oedometric consolidation, consolidated undrained (CU) triaxial, and falling head permeability. Tests were conducted for all mixtures, the soil, and WTS, with pointed-out exceptions. Results and Discussion: The results showed that the fine-grained WTS filled the soil voids but rearranged soil particles, thus, compacted dry unit weight decreased with WTS addition, probably due to its chemical composition with high amounts of aluminium and silica. The compressibility of the compacted mixtures did not differ significantly compared to the soil, while the shear strength analysis demonstrated a reduction in cohesion and an increase in the effective internal friction angle proportional to WTS addition. Hydraulic conductivity increased with WTS until 10% of residue introduction, decreased for 15%, and continued to decrease for 20%, reaching optimum permeability at 15%. Conclusion: The incorporation of WTS can improve or just not interfere with soil’s properties to be used as liner material in solid wastes storage facilities, mining ponds and soil-based wastewater treatment technologies. Furthermore, 15% of WTS (15:85% mixture) incorporation provided the best results meeting the hydraulic conductivity requirement for liner materials, i.e., equal, or lower than 10-9 m/s. The reuse of WTS for this purpose would allow producing a new added-value material in the scope of circular economy.

Experimental study of the shear behaviour of a multilayer geosynthetic liner system

Landfill stability is closely related to the shear strength of liner systems. Traditional interface shear tests at a single geosynthetic/geosynthetic or soil/geosynthetic interface cannot fully reflect the interactions between multiple geosynthetics within liner systems. To date, shear test data on composite liners that contain more than two geosynthetics are limited. This paper presents an experimental study of the interface shear behaviour of a multilayer geosynthetic liner consisting of a drainage geocomposite (GC), a textured geomembrane (GMB), and a needle-punched geosynthetic clay liner (GCL). It is revealed that the failure surface was transferred from the GCL interior to the GMB/GCL interface during the hardening stage. Higher displacement rates led to higher peak strengths, but a displacement rate of 0.1 mm/min yielded significantly higher residual strengths as this provided nearly drained conditions. Furthermore, three single interfaces contained in the composite liner were also tested, and the comparative analyses indicate that the macro shear strengths of multilayer liners can be roughly estimated with the test results of a single-failure interface.

Optimizing the liners thickness to design a landfill

Abstract Management of solid waste and leachate migration is a challenging task all over the world. Leachate was a fluid material produced during decomposition process contains heavy metals, high concentrations of organic compounds etc., contaminates soil and groundwater. Landfills are designed and constructed with liners to avoid the heavy metals transverse into the ground. Liner is a compacted layer of clay and Geosynthetic materials of various designed thicknesses preferred to the specified landfills. Present study is on the design of various liners with varying thicknesses for a landfill using numeric model using CTRAN/W clone in Geostudio software. Clay and Geosynthetics materials are used as liners and bore wells are provided at different radial distances with varying depths from landfill. Lead (Pb) and Cadmium (Cd) are assigned as contaminants on the liners. From the results, it has been observed that concentrations of Pb and Cd are decreasing with increase in liners thicknesses for both compacted clay liner (CCL) and Geosynthetic material liner. Duration of Pb and Cd concentrations to reach the bore wells is also increases. The specified liner thickness is analyzed after the comparison of concentration at end of liners, with and without using Geosynthetics to design a landfill. Time of concentration of Cadmium (Cd) is greater than Lead (Pb).

Interaction between PFASs and geosynthetic liners: current status and the way forward

This paper gives an overview of the current state of the practice on the interaction between geosynthetic liners and per- and polyfluoroalkyl substances (PFASs). The importance of PFAS chemistry and the need to make a clear distinction between on-site repositories and landfill applications is highlighted, as the liners will be subjected to widely different concentration loadings and types of dominating PFASs. Consequently, the selection of geosynthetic liner components needs to account for these differences and distinguish between the expected exposure conditions. In particular, geomembranes need to be selected carefully as their resin type will dictate their performance. Preliminary hydraulic conductivity test results using unamended and activated carbon amended geosynthetic clay liners indicate they can play a role in minimising the migration of PFAS, although the tests are still ongoing.

Geosynthetic liner integrity and stability analysis for a waste containment facility with a preferential slip plane within the liner system

The paper examines the effects of settlement-induced downdrag on geosynthetic liner systems for a waste containment facility with steep side slopes for different design scenarios, and conducts the stability analysis of the waste mass during waste filling operations. Without the presence of a reinforcing layer above a geomembrane (GMB) liner, the liner experiences unacceptable tensile strains under both short- and long-term downdrag waste settlements. It is shown that an anchored high strength/stiffness geotextile (HS-GTX) reinforcement over the GMB can reduce the GMB tensile strains to less than 3%, but the HS-GTX itself may be overloaded. A geosynthetic slip layer over the full or partial HS-GTX reinforcement overlying the GMB can reduce the tensile strains of the GMB to less than 3% and of the HS-GTX to less than 5% by providing a preferential slip plane between the geosynthetic slip layer and the HS-GTX. A rupture of the geosynthetic slip layer is likely to occur resulting in the exposure of the HS-GTX to the waste, but the protection of the GMB by the HS-GTX is still expected. The results from the stability analysis show that, during waste filling operations under a given factor of safety, there is a critical relationship between the width of the top of the waste pile and the total waste thickness.

Biocementation technology for construction of artificial oasis in sandy desert

Artificial oasis could be supported by the trapping and retaining rainfall water by impermeable layer of artificial material. In case of average annual rainfall in Arabian or Pakistani Deserts of 100 mm the watershed area must be at least 1000 ha to ensure rainfall water supply for consumption and irrigation in the artificial oasis of 100 ha area. Minimum cost for the sealing of 1000 ha of the sand slopes with 1 mm geosynthetic liner is about 112 mln Saudi Arabian Riyal, which could be not acceptable price for 100 ha of artificial oasis land. However, this cost could be diminished to 17 mln Saudi Arabian Riyal if to coat watershed slopes with 1 mm of biocemented sand crust using a low viscosity solution of biocement. Conventional cementation is cheaper but it cannot be used to make 1 mm sand crust because of a high viscosity of the cement suspension. The novel biotechnological method is based on the formation of the sand surface crust for water collection and transportation on the surrounding slopes. Most environmentally friendly biotechnology for this biocementation is aerobic biooxidation of cheap calcium formate or calcium acetate. Biocementation of the sand crust could be used to make a low-cost artificial desert oasis fed by rainfall.

Modelling deformation and strains induced by waste settlement in a centrifuge test

A numerical model to estimate the tensile strains (loads) of the geomembrane liner in the waste containment facility due to waste settlement is presented. A centrifuge test of the geomembrane-lined landfill is used to validate the numerical model. The calculated surface settlement at the centre of the landfill and the geomembrane tensile strains on intermediate benches are generally in good agreement with the measured data. Parametric analyses associated with foundation shear strength as well as interface shear strength and stiffness are performed. The influence of geometric nonlinearity on the geomembrane tensile strains is also examined. The numerical analyses indicate that the maximum geomembrane tensile strain occurs at the crest of the side slope near the intermediate bench for the cases and conditions examined. The lessons learned are likely to be useful to landfill design engineers using numerical models to aid in the design of the geosynthetic liner system for the waste containment facilities.

Research on shear strength of needle-punched GCL by simple-shear of composite liner

Geosynthetic composites are widely used in landfill liners owing to their excellent impermeability. However, translational failure along a multi-layered geosynthetic liner system is a major concern for the slope stability of landfill liners. Reasonable determination of the liner shear strength is vital for analysis of landfill stability. For this purpose, large-scale shear tests of a geosynthetic clay liner (GCL) overlying a geomembrane were performed without forcing shear failure to occur along a pre-determined failure plane. Different failure modes are obtained according to the interface and internal displacements of the GCL. The inflection point phenomenon is observed at small displacements on the shear stress versus displacement curve of hydrated needle-punched (NP) GCL. This is confirmed to be an inherent feature of hydrated GCL through experimental analysis. The shear mechanism of hydrated NP GCL is analyzed based on the inflection point phenomenon on the stress-displacement curve. The peak shear strength of a NP GCL can be divided into contributions from two components i.e., bentonite and reinforcement. A peak shear strength model that can reflect the failure mechanism is proposed considering each shear strength contribution of the GCL.

Development of a numerical model for performance-based design of geosynthetic liner systems

A numerical model for performance-based design of the geosynthetic elements of waste containment systems has been developed. The model offers a rational alternative to the current state of practice for design of geosynthetic containment system elements in which neither the strains nor the forces in liner system elements are explicitly calculated. To explicitly assess the ability of the geosynthetic elements of a containment system to maintain their integrity under both static and seismic loads, a large strain finite difference model of waste-liner system interaction was developed. Modular features within the model allow the user to select the appropriate features required for any particular problem. A beam element with zero moment of inertia and with interface elements on both sides is employed in the model to represent a geosynthetic element in the liner system. This enables explicit calculation of the axial forces and strains within the liner system element. Non-linear constitutive models were developed to represent the stress-strain behavior of geomembrane and geosynthetic clay liner beam elements and the load-displacement behavior of the beam interfaces. The use of the various features on the model is illustrated using available experimental data, including shaking table test data on rigid and compliant blocks sliding on geomembranes. Analysis of geomembranes subject to waste settlement and subject to seismic loading demonstrate applications of the model and provide insight into the behavior of geosynthetic liner system elements subject to tensile loads.

Geosynthetic Liner as Foundation Isolation for Seismic Protection

The effectiveness of a nonwoven geotextile–geomembrane liner as a foundation isolation system for RC buildings is studied analytically by considering artificial as well as recorded accelerogram as earthquake ground input motion. The concept of foundation isolation is applied by separating the foundation from the soil by a sliding friction interface in the form of geotextile–UHMWPE. A 3D finite element simulation and parametric study in ABAQUS have been carried out to estimate the effectiveness of the proposed method. The results show that through slip deformation, the interface reduces seismic energy transferred, reducing the dynamic response of the building. On an average, the proposed scheme can reduce the horizontal ground acceleration by 40%.

Seismic in-Soil Isolation of Solid Waste Landfill Using Geosynthetic Liners: Shaking Table Modeling of Tehran Landfill

Seismic loads may damage municipal solid waste (MSW) landfills through the relative movements within the landfill system. These movements can disrupt performance of drainage and gas collection systems, thereby resulting in environmental pollution. The smooth synthetic materials might be placed beneath the structures to provide seismic protection by absorbing the imparted energy of earthquakes through the sliding mechanism. It has been found that a high strength geomembrane placed over the other smooth and lubricated geomembrane sheets constitutes an efficient seismic liner. In the present study, experimental investigations were conducted to evaluate role of in-soil base isolation on seismic response of the Tehran MSW landfill. Results of geophysical and geotechnical investigations in the landfill site are presented in detail. Shaking table tests were conducted on the MSW embankment isolated by semi-elliptic shaped liners and subjected to harmonic sinusoidal base excitations. The results for the isolated and non-isolated cases are compared in terms of permanent displacement and seismic response. It has been observed that at all elevations the spectral accelerations within the waste decreased by base isolation, especially for the more intense excitations. Results of the present study demonstrate a suitable application of geosynthetic liners for seismic retrofitting of landfills.

Optimum Tensile Strength of Geomembrane Liner for V-Shaped Anchor Trenches Using Target Reliability Approach

This paper presents the target reliability based design framework for V-shaped anchored trenches to resist the sliding action and pull-out of geosynthetic liners. V-shaped anchor trenches are subject to various uncertainties arising from inconsistency in parameter estimation, improper compaction of cover/backfilled soils, field construction practices, the assumption of relative slippage at soil-liner interface and invention of new design methods. Therefore, based on the compilation of interface friction angles between different types of geomembranes (GMB) and granular soils according to several published studies, the mean, standard deviation, and coefficient of variation are computed using statistical analysis. Moreover, a framework for reliability based design is presented by considering the unit weights of backfill and cover soil, interface friction angle and allowable GMB tensile force. The optimum allowable GMB tensile force needed to maintain the stability against pull-out failure by targeting various reliability indices is obtained for various design parameters. The obtained results highlight the potential benefits of reliability methods and encourage their implementation during the design of MSW landfills.

Barreiras de impermeabilização: configurações aplicadas em aterros sanitários

With the growth of cities and expansion in the generation of municipal solid waste are becoming increasingly common the presence of landfills. These landfills must be made with waterproof barriers (liners) able to contain leachate, thereby preventing scattering of contamination plumes. In this sense, this study aims to list the major liners found in landfills, presenting their features, in addition to exposing examples applied in landfills across the country. To this end, it conducted a literature finding the different existing liners and their respective peculiarities. With the study we observed the presence of waterproof barriers consist of: geosynthetics, sludge, active barriers, municipal solid waste, benthic geocomposite, soil cement or compacted soils. It was also found that some Brazilian cities, as the case of Belo Horizonte, use to disposal landfill waste with the presence of alternative waterproofing layers. As a whole, the liner with the highest security among the classes studied were the geosynthetic liners combined with compressed ultisols, thus presenting lower permeability.

Review on performance of geosynthetic liners in municipal solid waste landfills

Review on performance of geosynthetic liners in municipal solid waste landfills

Critical interfaces in geosynthetic multilayer liner system of a landfill

This study is to identify the critical interface in a geosynthetic multilayer liner system by examining the effects of the interface shear strength of liner components, leachate level, leachate buildup cases, and peak and residual interface strengths. According to current landfill design procedures, conducting stability analysis along the same interface at both the back slope and base may result in a non-conservative result. The critical interfaces with the minimum factor of safety are generally found at different locations along the back slope and base. The critical interface for a multilayer liner system cannot simply be assumed during stability analysis. It can shift from one interface to another with changes in the leachate level and with different leachate buildup cases. The factor of safety for an interface with a high friction angle and low apparent cohesion generally drops much more quickly than it does under inverse conditions when the leachate level increases. The failure interface in a liner system under residual conditions is usually different from the failure interface under peak conditions.

Observations of bentonite erosion from solar-driven moisture migration in GCLs covered only by a black geomembrane

ABSTRACT: Manufacturers of geosynthetic liner materials recommend that composite geomembrane/geosynthetic clay liners (GCLs) be covered in a timely fashion to avoid potential issues that may arise under the action of long-term solar exposure. In this paper, field evidence of a new, never before reported solar-exposure driven damage mechanism for GCLs covered only by a black geomembrane and left exposed for more than 3 years is presented. Solar exposure can give rise to a large daily variation in geomembrane temperature, which causes a moisture cycle within the interface between the geomembrane and GCL resulting in the formation and flow of condensed moisture beneath the geomembrane. All four of the GCL products investigated at the Queen's University Environmental Liner Test Site were shown to have experienced significant bentonite erosion after 4.7 years of exposure. Erosion was identified in the field through a tactile survey of GCL panels in which the stiffness response of the GCL to touch was used to identify eroded zones. A change in the colour of the GCL, although useful to identify possibly eroded zones in some GCL products, proved ineffective in others. Erosion features were observed with widths up to and exceeding 200 mm across, making them unlikely to undergo self-healing upon hydration and application of normal stress. As a result, the observed erosion features would have severe adverse consequences for leakage rates through the GCL component of a composite liner barrier system. These observations provide yet another strong motivation for timely covering of composite landfill liner systems.