Landfill Liner Research Articles

Angle-based residual strength estimation between geotextile/textured geomembrane interface

Geotextile and geomembrane are widely used in landfill liner systems, but the relationship between geomembrane roughness and geotextile/geomembrane interface residual shear strength remains to be studied. In this paper, by using a large-scale ring shear apparatus, a series of ring shear tests between geotextile/geomembrane was conducted, and the profile inclined angle distribution of the textured geomembrane surface was obtained by a profilometer. The experiment results showed that the geotextile/geomembrane interface has reached the residual status after a shear displacement of 3 m, and the average inclined angle of textured geomembrane was close to zero. With the increase of geomembrane asperity height, the interface residual strength increases. Through force analysis and statistical analysis, quantitative relationships between residual shear strength between geotextile/co-extruded geomembrane and geotextile/cone-shape structured geomembrane interfaces and inclined angle distribution were established. The model was validated by test results and case analysis. This study helps understand the mechanism that how the textured geomembrane surface caused high interface residual strength, and choose geomembrane with appropriate roughness to provide adequate residual strength in engineering applications.

Interface Dynamic Shear Characteristics of Aging GMB/CCL Composite Liner

Interface Dynamic Shear Characteristics of Aging GMB/CCL Composite Liner

Heat mitigation in basal compacted clay liners in municipal solid waste landfills.

In municipal solid waste (MSW) landfills, biodegradation of the organic MSW fraction results in elevated waste and basal liner temperatures which have the potential to cause the clay component of the basal liner to experience severe moisture loss over time and eventually undergo desiccation cracking. Cracking of the basal liner's clay component would result in an uncontrolled release of contaminants into the surrounding environment and ultimately give rise to a variety of major environmental concerns. Accordingly, this study examined the variation of temperature-moisture profiles along the depth of a compacted clay liner (CCL) exposed to different constant elevated waste temperatures (CETs) in the absence and presence of two heat reduction techniques, respectively. Rockwool insulation layers with varying thicknesses and galvanized steel cooling pipes with varying flowrates were introduced separately as the two heat reduction techniques. Introduction of both techniques led to a significant attenuation of the temperature rise and desiccation experienced by the CCL in the face of different CETs. An increase in rockwool thickness increments led to a progressive reduction of CCL temperature, while an increase in flow rate under turbulent condition did not have a significant influence on the temperature and desiccation reduction of the CCL. Nevertheless, the present study certainly highlights the potential of the two proposed heat reduction techniques to minimize desiccation and consequently increase the service life of CCLs exposed to different elevated temperatures in MSW landfills.

Complementary use of analytical equations and numerical models for composite liner designs

The finite element (FE) method is used to identify limitations and extend the applicability of an analytical solution for leakage through holed wrinkles in composite liners. The limiting assumption in the analytical model is relaxed based on FE results, providing a means of obtaining good agreement through the two methods over a wide spectrum of cases. Despite the flexibility of the FE, the analytical model has the advantage of readily accommodating a wide range of dimensions and material properties that, even with a very large mesh, may be difficult to analyze using FE. In addition, the analytical equation is well-suited for Monte Carlo simulation. This is illustrated by the use of the modified analytical equation and the Monte Carlo simulations to compare the performance of two types of composite liners currently approved for use in Chinese landfills with a generic design in Canada and other parts of the world. It is shown that even with a relatively small number of holed wrinkles leakage through the geomembrane composite liner can differ by up to two orders of magnitude between composite liners considered to be equivalent. The paper also notes the need to revise regulations to reflect the evolution of knowledge.

The strength and hydraulic conductivity characteristics of sewage sludge ash and natural soil mixtures – a sustainable alternate landfill liner material

ABSTRACT This paper examines the feasibility of the natural soil and sewage sludge ash (SSA) mixtures, which satisfy the criteria to be used as landfill liners. The effect of SSA content on hydraulic conductivity and strength characteristics of natural soil and SSA mixtures has been investigated through a series of laboratory tests. The results demonstrate that mixtures exhibit an increase in both hydrodynamic diffusion coefficient and strength with the increasing SSA content. With the content of SSA from 0% to 5%, the values of the hydrodynamic diffusion coefficient ( D ) ranged from 3.5 × 10−10 to 15 × 10−10 cm2/s. The increase in the hydrodynamic diffusion coefficient is minor for low SSA content and significant for SSA content exceeding 5%. The inclusion of 5% SSA content results in a hydrodynamic diffusion coefficient that is approximately three times higher than that observed in natural soil. The results were obtained from soil triaxial tests, revealing that the mixtures containing SSA exhibited a significant increase in both the initial tangent modulus and the ultimate principal stress difference compared to those of natural soil. The SSA content with the highest value exhibits maximum initial tangent modulus and ultimate principal stress. The comprehensive analysis of the strength and hydraulic diffusion conductivity of the mixtures demonstrates that the incorporation of 3% SSA results in a significant enhancement in strength, while marginally increasing hydrodynamic diffusion coefficients. Therefore, it can be inferred that the utilization of mixtures containing 3% SSA content as a liner material is suitable.

A Novel Landfill Liner Material for Solidified Lake Sediment Based on Industrial By-Product and Construction Waste: Engineering Behavior and Cr(VI) Breakdown Characteristics

Engineering sludge, industrial waste, and construction waste are marked by high production volumes, substantial accumulation, and significant pollution. The resource utilization of these solid wastes is low, and the co-disposal of multiple solid wastes remains unfeasible. This study aimed to develop an effective impermeable liner material for landfills, utilizing industrial slag (e.g., granulated blast furnace slag, desulfurized gypsum, fly ash) and construction waste to consolidate lake sediment. To assess the engineering performance of the liner material based on solidified lake sediment presented in landfill leachate, macro-engineering characteristic parameters (unconfined compressive strength, hydraulic conductivity) were measured using unconfined compression and flexible wall penetration tests. Simultaneously, the mineral composition, functional groups, and microscopic morphology of the solidified lake sediment were analyzed using microscopic techniques (X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy + energy dispersive spectroscopy). The corrosion mechanism of landfill leachate on the solidified sediment liner material was investigated. Additionally, the breakdown behavior of heavy metal Cr(VI) within the solidified sediment liner barrier was investigated via soil column model experiments. The dispersion coefficient was computed based on the migration data of Cr(VI). Simultaneously, the detection of Cr(VI) concentration in pore water indicated that the solidified sediment liner could effectively impede the breakdown process of Cr(VI). The dispersion coefficient of Cr(VI) in solidified sediments is 5.5 × 10−6 cm2/s–9.5 × 10−6 cm2/s, which is comparable to the dispersion coefficient of heavy metal ions in compacted clay. The unconfined compressive strength and hydraulic conductivity of the solidified sediment ranged from 4.90 to 5.93 MPa and 9.41 × 10−8 to 4.13 × 10−7 cm/s, respectively. This study proposes a novel approach for the co-disposal and resource utilization of various solid wastes, potentially providing an alternative to clay liner materials for landfills.

Modeling of the effect of gradation and compaction characteristics on the california bearing ratio of granular materials for subbase and landfill liner construction

The California bearing ratio (CBR) of a granular materials are influence by the soil particle distribution indices such as D10, D30, D50, and D60 and also the compaction properties such as the maximum dry density (MDD) and the optimum moisture content (OMC). For this reason, the particle packing and compactibility of the soil play a big role in the design and construction of subbases and landfills. In this research paper, experimental data entries have been collected reflecting the CBR behavior of granular soil used to construct landfill and subbase. The database was utilized in the ratio of 78–22% to predict the CBR behavior considering the artificial neural network (ANN), the evolutionary polynomial regression (EPR), the genetic programming (GP), Extreme Gradient Boosting (XGBoost), Random Forest (RF) and the response surface methodology (RSM) intelligent learning and symbolic abilities. The relative importance values for each input parameter were carried out, which indicated that the (CBR) value depends mainly on the average particle size (D30, 50 & 60). They showed a combined influence index of 66% of the considered parameters in the model exercise. This further shows the importance and structural influence of the particles within the D50 and D60 range in a granular material consistency in the design and construction purposes. Performance indices were also used to study the ability of the models. The ANN model showed the best performance with accuracy of 88%, then GP, EPR and RF with almost the same accuracies of 85% and lastly the XGBoost with accuracy of 81%. Also, the RSM produced an R2 of 0.9464 with a p-value of less than 0.0001. These values show that the ANN produced the decisive model with the superior performance indices in the forecast of CBR of granular material used as subbase and waste compacted earth liner material. The results further show that optimal performance of the CBR depended on D50 and D60 for the design of subgrade, subbase, and liner purposes and also during the performance monitoring phase of the constructed flexible pavement foundations and compacted earth liners.

DESIGN OF LANDFILLS AND THE UTILIZATION OF WASTES AS SUSTAINABLE LINER MATERIALS: A MINI-REVIEW

Modern landfills, designed to minimize environmental and health risks, play a crucial role in solid waste disposal. Poorly managed municipal solid waste facilities have severe environmental consequences, prompting intervention and remediation. Landfill construction is not enough; regular maintenance is essential to prevent harm. Landfills' historical evolution reflects societal needs, technological advancements, and environmental awareness. The 20th century saw engineered landfills with practices like compaction, daily covering, and leachate collection. Despite progress in recycling and incineration, landfills remain dominant, posing challenges like methane emissions, leachate contamination, and land use. Research emphasizes integrating landfills with recycling, composting, and waste-to-energy technologies for a sustainable future. Engineered landfills are advantageous over dumpsites, in terms of groundwater and air protection, odor control, energy generation, and job creation. Seismic analysis of landfills addresses deformation and seismic reactivity, emphasizing proper liner construction to reduce seismic impact. Leachate, a potential environmental hazard, requires careful management with effective liners to prevent groundwater and soil pollution. Various materials, including fly ash, paper mill sludge, waste foundry sand, recycled concrete aggregate, rice husk ash, and plastic waste, are reviewed for landfill liners. Research shows these materials can offer effective barriers, reducing environmental impact and promoting sustainability. Future studies should continue exploring alternative materials, considering factors like strength, hydraulic conductivity, and environmental protection.

Assessing the sustainability of composite liner systems for municipal solid waste landfills: a triple bottom line approach

Assessing the sustainability of composite liner systems for municipal solid waste landfills: a triple bottom line approach

Two-dimensional migration characteristics of contaminant through composite liner with arbitrarily distributed defects

Previous studies indicate that liner defects can significantly accelerate contaminant migration in landfill, shortening the migration time by orders of magnitude. Although the effect of defects upon contaminant migration and barrier capacity of liner system has been investigated based on several theoretical models, they are always limited to one-dimensional scopes. Here a two-dimensional (2-D) model was established for contaminant transport through composite liner to the soil layer, with geomembrane (GM) defects arbitrarily distributed along the horizontal direction, and then Laplace transform, Fourier transform, and boundary transform method were utilized to derive its semi-analytical solution, which was verified by experimental data and numerical results. The obtained solution can take nonuniformly distributed defects into account and demonstrates the 2-D contaminant concentration and flux profiles in the spatiotemporal domain. Computational results of the solution are employed to illustrate the roles of material coefficients and modeling sizes upon the variations of contaminant concentration and flux. Results support that contaminant migration is expedited by the GM defect in landfill, and geosynthetics clay liner can reduce the pollution level caused by GM failure. Moreover, the contaminant flux will not be significantly influenced by the defect positions, which, however, leads to non-negligible impact on concentration profiles.

Improving landfill liner performance with bentonite-slag blend permeated with ammonia for a Municipal solid waste landfill

Leachate emanating from landfills contains ammonia which may cause serious health effects on living things. An effectively designed clay barrier should not allow the contaminant to infiltrate the soil and groundwater systems. The utilization of certain industrial by-products in engineered landfill barriers, not only reduces the need for conventional liner materials but also helps in sustainable waste management. This study investigated the hydraulic conductivity, unconfined compressive strength, compaction, and adsorption characteristics of lithomargic clay blended with an optimum percentage of bentonite (10%) and granulated blast furnace slag (15%) permeated with ammonia. The results revealed that increasing the content of granulated blast furnace slag decreased the maximum dry density while increasing the optimum moisture content. In comparison to lithomargic clay, the hydraulic conductivity of the amended soil liner permeated with ammonia decreased from a value of 3 × 10−8 m/s to 5 × 10−10 m/s. The unconfined compressive strength of the amended soil specimens showed an increasing trend with curing times (i.e., 0, 14, 28, and 56 days). The batch adsorption results revealed that Freundlich and Langmuir's isotherm fits the equilibrium adsorption data and the adsorption of ammonia on clay liner follows non-linear behaviour. Overall, the experimental results implied that lithomargic clay blended with 10% bentonite and 15% granulated blast furnace slag can be used as an impermeable soil reactive barrier in engineered landfills.

Cation exchange capacity- An alternative method to investigate the geological barrier for landfills?

Clays and clay minerals are ideal raw materials for geological barriers and landfill liners because of their low-hydraulic permeabilities, their swelling properties and adsorption capacities. The geological barrier is a supplementary barrier beneath the body of the landfill, intended to protect the environment from uncontrolled leachate from the waste material. An Austrian standard defines the process for site exploration and the required laboratory tests and parameters for the analysis of the geological barrier. The most important laboratory tests besides grain size analysis are the Atterberg limits and the determination of the clay mineralogy using X-ray diffraction. However, the analysis of the cation exchange capacity (CEC) is not included in the list of laboratory tests. CEC is a numerical value that describes the physical properties of clays, such as the diffusion of charged and uncharged molecules and the cation retention. Hence, the objective of this study is to clarify whether the determination of the CEC using the Cu-trien method represents a possible alternative to currently used laboratory tests.For this purpose, three samples (loess, sand and clay) from two landfill sites owned and operated by Zöchling GmbH as well as six mixtures of these samples with varying compositions were examined for their mineralogical, chemical and geotechnical properties. The samples consisted of varying amounts of quartz, feldspar, calcite, dolomite and the clay minerals smectite, illite, kaolinite, vermiculite and chlorite. The results showed that the bulk clay mineralogy correlates well with the Atterberg liquid limit (R2 = 0.73) and the CEC (R2 = 0.88) and furthermore, the results of the two methods – Atterberg liquid limit and CEC- even correlated better (R2 = 0.95).This demonstrates that the CEC can be an alternative to the Atterberg liquid limit and/or the analysis of the mineralogical composition of the material. Advantages of the CEC are rapidness, its good reproducibility and cost-efficiency of the analyses compared to the other two methods. Based on the results of this study, a partial substitution of the currently used laboratory tests is considered feasible and CEC could at least be used for fast and efficient screening.

Investigation of a novel hydraulic tunnel composite lining with polyurea coating interlayer

PurposeMultilayer composite liner structures are the primary structural form of hydraulic tunnels. However, the bearing mechanism of multilayer composite liners has not been investigated thoroughly. Many existing design schemes do not properly achieve a balance between structural safety, anti-seepage capacity, and cost effectiveness. Thus, a new composite liner structure type and its theoretical model was proposed.Design/methodology/approachA novel hydraulic tunnel composite liner structure with a polyurea spray coating interlayer was proposed in this study. A theoretical model based on the state-space method was developed and verified using FEM models and existing theoretical models. Parametric analysis was conducted based on the theoretical model to investigate the influence of various variables, including interfacial shear stiffness, inner liner thickness, and outer liner elastic modulus.FindingsIt was concluded that the proposed theoretical model can be used successfully to calculate multilayer composite liner structures with high calculation efficiency. The overall deformation stiffness of the composite liner system increased with the interfacial shear stiffness. The sprayed coating interlayer significantly affects the residual force distribution between the outer and inner liners, which can also be affected by the adjustment of the thickness of the outer and inner liners. Thus, attention should be paid to these factors in the rational design of the proposed composite liner system.Originality/valueWith the development of China’s water conservancy projects, complex geological conditions, high surrounding rock stress, high internal and external water pressures, and other unique application scenarios have gradually increased. This places higher requirements on the bearing performance and impermeability of hydraulic tunnel lining structures. On the other hand, conventional hydraulic tunnel lining structures can hardly achieve a satisfactory balance between economy, structural safety, and impermeability. Thus, the proposed structure has the potential to be used in a wide range of applications.

Evaluating the Performance of Modified Geo-Synthetic Clay Liners

Waste products from human activity must always be controlled. Reusing some garbage is possible. But a lot of rubbish that could be more useful needs to be disposed of to protect the environment. Landfilling is one popular form of disposal. The most frequent issues with landfills are groundwater contamination and environmental deterioration, brought on by rainfall and leachate generated during the breakdown of organic materials. A landfill's liner is crucial to stop leachate migration and groundwater contamination. Since their development in 1986, Geo-Synthetic Clay Liners (GCLs) have gained popularity as a barrier solution for municipal solid waste landfills. In this study, fly ash and Kaolinite, two waste materials, are combined with bentonite in different percentages 10–30% and 50%, respectively to evaluate their potential usage as liner materials. Bentonite, in combination, is anticipated to function as a low permeability, self-healing, hydraulic barrier due to these swelling qualities.

Automated manufacture and experimentation of composite overwrapped pressure vessel with embedded optical sensor

In recent years, the mobility (air/land) industry has been developing fuel-cell vehicles for mass adoption as hydrogen technology matures. Compared to conventional metallic design, the composite overwrapped pressure vessel without a metal or polymer liner results in a lightweight solution for gaseous hydrogen storage which further improves fuel efficiencies. Since the capabilities of automated fiber placement for making multi-stiffened structures are distinct from other automated manufacturing techniques, this study aimed to evaluate the feasibility of implementing AFP into the manufacture of a small scale COPV with a partially composite liner. The manufacturing related challenges are identified and discussed. During the manufacturing process, Distributed fiber optic sensor was embedded between the plies, as a structural health monitoring solution, to monitor the mechanical performance of the pressurized tank. In addition, finite element study was done to predict the internal strains for different pressure levels and the measured experimental strains at the sensor's location are found to be in close agreement with the finite element results. It is shown that such sensors can be integrated into automated fiber placement manufactured tanks for internal strain monitoring.

Damage evolution determined by material mass distribution of reactive material-metal composite jet impacting multi-spaced plates

The reactive material-metal composite jet (RMM-CJ), exhibiting a dual penetration-enhancement effect is of growing concern. In the present study, the composite jets of reactive material-copper (RM–Cu), reactive material-titanium (RM–Ti), and reactive material-aluminum (RM–Al) impacting multi-spaced plates were studied experimentally and numerically. A comprehensive analysis of the damage effects was conducted based on experimental and simulation results. The results show that the damage area of each layer of plate is closely related to the mass distribution of reactive material. The relationship of the mass of each layer of reactive material with time is given, and the deflagration gain is quantified. The research results provide a useful reference for the design and optimization of reactive material-metal composite liners.

Estimating the strength of soil stabilized with cement and lime at optimal compaction using ensemble-based multiple machine learning

It has been imperative to study and stabilize cohesive soils for use in the construction of pavement subgrade and compacted landfill liners considering their unconfined compressive strength (UCS). As long as natural cohesive soil falls below 200 kN/m2 in strength, there is a structural necessity to improve its mechanical property to be suitable for the intended structural purposes. Subgrades and landfills are important environmental geotechnics structures needing the attention of engineering services due to their role in protecting the environment from associated hazards. In this research project, a comparative study and suitability assessment of the best analysis has been conducted on the behavior of the unconfined compressive strength (UCS) of cohesive soil reconstituted with cement and lime and mechanically stabilized at optimal compaction using multiple ensemble-based machine learning classification and symbolic regression techniques. The ensemble-based ML classification techniques are the gradient boosting (GB), CN2, naïve bayes (NB), support vector machine (SVM), stochastic gradient descent (SGD), k-nearest neighbor (K-NN), decision tree (Tree) and random forest (RF) and the artificial neural network (ANN) and response surface methodology (RSM) to estimate the (UCS, MPa) of cohesive soil stabilized with cement and lime. The considered inputs were cement (C), lime (Li), liquid limit (LL), plasticity index (PI), optimum moisture content (OMC), and maximum dry density (MDD). A total of 190 mix entries were collected from experimental exercises and partitioned into 74–26% train-test dataset. At the end of the model exercises, it was found that both GB and K-NN models showed the same excellent accuracy of 95%, while CN2, SVM, and Tree models shared the same level of accuracy of about 90%. RF and SGD models showed fair accuracy level of about 65–80% and finally (NB) badly producing an unacceptable low accuracy of 13%. The ANN and the RSM also showed closely matched accuracy to the SVM and the Tree. Both of correlation matrix and sensitivity analysis indicated that UCS is greatly affected by MDD, then the consistency limits and cement content, and lime content comes in the third place while the impact of (OMC) is almost neglected. This outcome can be applied in the field to obtain optimal compacted for a lime reconstituted soil considering the almost negligible impact of compactive moisture.

Tribological Properties of Polytetrafluoroethylene (PTFE)/Aramid Fabric Composite Liner Modified by PAO40/Polysulfone/SiO2 Hybrid Shell Microcapsules

Hybrid shell microcapsules have been incorporated into polytetrafluoroethylene (PTFE)/aramid fabric composite liners to enhance the tribological behavior of self-lubricating spherical plain bearings. PAO40/polysulfone/SiO2 hybrid shell microcapsules were synthesized utilizing a combination of Pickering emulsification technology and solvent evaporation. The modified liner with 9 wt% microcapsules exhibited the highest reduction in the average friction coefficient and wear rate, which were 31.1% and 47.9% lower than the unmodified liner. Furthermore, the tribological behavior of modified liners was investigated under different loads and sliding speeds. The friction process of the modified liner and the formation process of the transfer film were analyzed. Investigations into the friction reduction mechanism revealed that the PAO-40# released from microcapsules transitioned the friction type from dry to mixed. SiO2 particles are conducive to forming a denser transfer film by the PTFE abrasive. The results of this study have important scientific significance.

Simplified methods for the design of landfill double composite liners using neural network

Double composite liners (DCLs) have been widely used in landfills to protect the surrounding environment. This study aims to develop simplified empirical equations for calculating breakthrough times of DCLs based on analytical equations or experimental data. The artificial intelligence neural network called Group Method of Data Handling (GMDH) type neural network was used to perform equation simplification. New empirical equations in polynomial formats are obtained by a layer-summation method and a series of numerical experiments based on analytical solutions for contaminant transport in double composite liners. The accuracy of empirical equations is demonstrated by comparing them with the existing solutions and numerical results. The performance of four types of DCLs were then investigated. The mean absolute percentage errors (MAPEs) for each type of DCLs with different leachate heads and soil liner thicknesses are all lower than 10%. Additionally, a trend for the improvement of the GMDH equation accuracy with the increase of Δh1 is observed. The presented equations can perform well in high leachate head conditions (e.g. > 5 m) where DCLs are required.

Exploring the viability of Bentonite-amended blends incorporating marble dust, sand, and fly ash for the creation of an environmentally sustainable landfill liner system

The development of effective and cost-efficient landfill liners is crucial to prevent groundwater contamination from leachate, safeguarding soil quality and the environment. Composite liners, particularly those combining bentonite with supplementary materials such as fly ash or marble dust, present a promising solution. This study delves into a comprehensive investigation of the physical properties of landfill liners composed of bentonite-fly ash and bentonite-marble dust mixtures through an extensive series of laboratory tests. The research systematically analyzes various proportions of bentonite with fly ash and marble dust, evaluating their impact on liner performance in comparison to Bentonite-sand mixtures. Physicochemical analyses are employed to understand the interactions and behaviors of these distinct substances within the amended bentonite. A wide array of physical properties, including Atterberg’s limits, compaction characteristics, free swell index, modified free swell index, California bearing ratio, cohesion, and angle of internal friction, are meticulously examined. Collectively, these properties offer a comprehensive overview of the suitability and performance potential of bentonite-fly ash and bentonite-marble dust mixtures as landfill liners, presenting a viable alternative to traditional bentonite-sand mixtures. The study reveals synergistic effects between bentonite and both fly ash and marble dust, highlighting their significant contributions to enhancing the physical traits of landfill liners. This advancement in landfill liner design holds the promise of effectively mitigating detrimental environmental impacts associated with waste disposal. While this study provides a robust foundation, it is essential for future investigations to prioritize long-term performance assessments and real-world implementation. Validation and fine-tuning of these findings are crucial to ensuring practical applicability and efficacy within authentic landfill construction scenarios. This holistic approach will contribute to the continued evolution and optimization of landfill liner design, addressing the pressing challenges of sustainable waste management and environmental protection.