The contaminant transport of chloride through a single composite liner facility comprised of a geomembrane (GMB) with holed wrinkles over a compacted clay liner (CCL) and an aquitard underlain by an aquifer is examined. A two-dimensional finite element (2D FE) model (HYDRUS-2D) was employed for simulating variably saturated contaminant transport. Parametric analyses under saturated and unsaturated conditions explored the effects of geometric parameters, including aquitard and CCL thicknesses, the number of holed wrinkles per hectare, and wrinkle spacing, on peak chloride concentrations at the aquifer’s outlet. Results showed that while CCL thickness plays an important role in controlling contaminant transport, thicker aquitards are more effective, through creating unsaturated conditions, which decreases hydraulic conductivity of the layer. Increasing holes from 1 to 5 per hectare raised peak aquifer concentrations from 10.8 mg/L to 29.4 mg/L. Closer spacing between two holed wrinkles increased aquifer contaminant levels from 16 mg/L to 30 mg/L by enhancing saturation level and hydraulic conductivity. Unsaturated conditions created by thicker aquitards showed greater sensitivity to increased flow caused by GMB failure, as peak aquifer concentrations increased from 16.2 mg/L (no GMB rupture) to 31.4 mg/L (GMB rupture at 150 years), compared to saturated conditions.

From waste to barrier: A mini-review of geopolymer-modified soil as environmentally sustainable landfill liner material.

The effect of temperature and salinity on permeability and hydraulic conductivity evolution of clayey liners in solid waste landfills.

Assessment of Coupled Consolidation and Contaminant Transport on the Performance of Cationic Surfactant–Modified Bentonite-Loess Landfill Liners

ABSTRACT Valley‐type landfills in mountainous regions like China utilize sloped composite liners (geomembrane over geosynthetic clay liner, GMB/GCL) to maximize waste capacity. However, high leachate heads and slope‐induced GCL erosion defects significantly increase leakage risks. Although models exist for horizontal liners or isolated GMB defects, no analytical solution quantifies leakage through combined GMB wrinkles and GCL erosion defects on slopes. This study develops a novel analytical model to predict leakage for two critical defect configurations: (1) GCL defect downstream of a GMB defect, and (2) GCL defect upstream of a GMB defect. Solutions are derived from coupled flow equations and validated against finite‐element simulations. Within the studied slope range (0°–45°) and interface contact conditions, key findings demonstrate: negligible net impact of slope angle on total leakage (<0.3% variation); leakage increases of up to 32% (poor contact) and 13% (good contact) due to GCL defects versus defect‐free liners; manageable 3D effects from defect length/orientation (≤22% leakage increase); and critically, no practical impact of GCL defect position (upstream/downstream) on total leakage. These insights enable simplified analysis ( α = 0°) for field‐realistic along‐slope defects and support probabilistic leakage assessments to optimize liner design in slope applications.

The safe containment of hazardous waste requires landfill liner materials with both effective radiation shielding and strong hydro-mechanical performance. This study investigates the potential of a bentonite-goethite mixture as a novel material for hazardous waste landfill liners. The study examines the radiation shielding of the mixtures, represented by the linear attenuation coefficient, through experimental (Na (Tl) spectrometer detector), numerical (MCNP code), and reference database (XCOM and PHY-X) approaches. Moreover, the hydraulic permeability and mechanical properties are evaluated experimentally. For this, the varying proportions of goethite from 10 to 50% were examined. The results show an increase of up to 20, 24, and 28 percent in the linear attenuation coefficient at gamma ray energies of Cs^{137} (661.6 keV) and Co^{60} (1173.2 and 1332.5 keV). Higher goethite percentages, correlating with density variations and enhancing radiation shielding effectiveness. Numerical and reference database results align closely with experimental findings, suggesting their utility for assessing other mixtures. The direct shear test reveals that with an increase of goethite proportion to 50 percent, the cohesion is reduced to half and the friction angle is inclined twice the pure bentonite values, attributed to bentonite reduction and goethite roughness. Unconfined compressive strength trends show 20% improvement at specific mixture composition with 30% goethite, while hydraulic conductivity inclines with goethite content to mathrm { 8.8times 10^{-10}} m/s. In this study the bentonite-goethite mixture illustrates improving radiation shielding and maintaining hydro-mechanical properties for landfill liners. This may offer a sustainable alternative using waste materials from mineral processing, contributing to waste management and environmental sustainability.

Rapid urbanisation and population growth have resulted in the generation of 2.01 billion tonnes of municipal solid waste (MSW) globally each day. Incineration is a widely used method to reduce the mass and volume of this waste, however it produces substantial amount of residual ash that requires further treatment before it can be safely used in geotechnical engineering applications. The large volume of municipal solid waste incineration (MSWI) ash generated poses significant challenges, occupies valuable landfill space, and complicates waste management efforts. This study investigates the reuse potential of MSWI ash (both bottom ash and fly ash) as a sustainable landfill liner material. A comprehensive analysis of the chemical, physical, and geotechnical properties of MSWI ash was conducted, revealing typical ranges such as maximum dry density (MDD) of 10.8–17.6 kN/m3, optimum moisture content (OMC) of 10.8%–45.7%, permeability ranging from 10−9 to 10−3m/s, friction angle from 20.8° to 54.5°, and cohesion values of 0–52.4 kN/m2. The presence of minerals like calcite and quartz contributes significantly to strength characteristics. To meet the low permeability requirements for landfill liners, MSWI ash has been blended with bentonite, which enhances its barrier performance. Leaching studies highlight the influence of pH on the release of heavy metals, emphasising the need for stabilisation techniques. Various stabilisation methods have been demonstrated to effectively immobilise hazardous constituents including heavy metals and dioxins. The findings suggest that MSWI ash can play a key role in promoting sustainable waste management by immobilising contaminants and mitigating the environmental and health risks associated with its disposal. By integrating MSWI ash into engineering applications, this sustainable approach not only reduces the environmental footprint of waste management, but also offers innovative solutions for the reuse of industrial by-products.

ABSTRACT Expansive soils are problematic to geotechnical engineers when subjected to thermal loads with their swell-shrink behaviour. Bentonite clays, often used as liners in landfills, are more susceptible to changes in temperature with high levels of montmorillonite, which can cause desiccation, which in turn affects their geotechnical stability. In this study, desiccated crack patterns of 12 clay samples with varying liquid limits are analysed via a novel desiccation methodology using Image Analysis to form a relationship between liquid limit and crack parameters. Optical microscopy images of the clay samples are further analysed to evaluate the true particle size parameters of the clay samples. An empirical relationship is established between the true particle size parameters and the liquid limit of the clay samples, which is used to formulate a relationship between true particle size parameters and crack parameters. A validation study was conducted on six naturally occurring clays from various parts of north India. The formulated logarithmic relationship between crack area and maximum Feret diameter was observed to vastly overestimate the crack area of naturally existing clays, while the logarithmic correlation between other crack parameters and true particle size parameters was validated with a reasonable degree of agreement.

Predicting the hydraulic conductivity of fly ash-clay landfill liners with interpretable ensemble learning

Geosynthetic clay liner for coal combustion product landfill: An environmental impact assessment.

This study examines key bioprocess parameters influencing the reduction in hydraulic conductivity in porous media via Microbially-Induced Calcite Precipitation (MICP), highlighting its relevance to environmental engineering applications such as bio-barriers and landfill liners. Sporosarcina pasteurii was utilized as the ureolytic bacterium to induce calcium carbonate precipitation under controlled laboratory conditions. Experimental variables included bacterial cell density (OD600), diameter of glass beads, concentrations of precipitation solution, bentonite, and yeast extract. A total of 42 experimental runs were conducted based on a custom design in Design-Expert software. Hydraulic conductivity was selected as the response variable to evaluate treatment performance. Response surface methodology (RSM) was applied to develop a second-order polynomial model, with statistical analyses indicating a strong model fit (R2 = 0.948, adjusted R2 = 0.929, predicted R2 = 0.868). ANOVA confirmed the significance of the main effects and interactions, particularly those involving glass bead diameter and OD600. Among the tested factors, the precipitation solution exhibited the strongest individual effect, while bentonite and yeast extract demonstrated supportive roles. Optimization revealed that a balanced combination of microbial density and chemical inputs minimized hydraulic conductivity to 0.0399 cm/s (≈95% reduction), with an overall desirability score of 1.000. Laboratory-scale experiments demonstrated field-scale applicability, underscoring the potential of biotechnological soil treatment and empirical modeling for developing sustainable low-permeability barriers.

To mitigate vibration in thin-walled composite combustion liners of aero-engines, this study proposes an optimization strategy for stiffener design to maximize natural frequencies and suppress resonance. The approach enhances structural dynamics by installing transverse and longitudinal stiffeners along the tubular wall, with their dimensions and orientations systematically optimized. Design variables were chosen: combustion liner wall thickness, stiffener thickness, transverse stiffener width/angle, longitudinal stiffener width, and composite lamination layup scheme. The orthogonal experiments were completed and followed by range analysis and variance analysis. The results demonstrated that wall thickness had the most significant impact on the natural frequency, and the 45° lamination scheme showed a superior performance compared to other configurations. Finally, a predictive equation was developed using a multiple linear regression model. The optimized stiffener configuration markedly enhances natural frequencies, mitigating vibration-induced instability. This methodological framework provides a systematic basis for designing optimized stiffener layouts in composite combustion liners for aero-engines.

Bayesian updating for improving long-term performance prediction of composite liners in landfills with temporally variable leachate head

Uncertainty propagation analysis of defects-induced leakages through composite liners in landfills

Characterization and experimental modeling of rockwool, hot-sprayed polyurea, and casted polyurea as thermal insulation for heat mitigation in landfill liner

Ti3C2Tx hierarchical stereostructure for innovatively synchronous enhancement on wear resistance and corrosion protection of fabric/phenolic composite liners

Landfill liners as a source of microplastics: Do the guards guard themselves?

Abstract Desiccation cracks in clay soils are a serious problem in landfill liner. This study aims to evaluate the behaviour of soil cracks in fly ash-bentonite mixtures as land-fill lining materials under wet-dry cycles and analyse the crack intensity using a quantitative approach in the form of Crack Intensity Factor (CIF). The methods used in this study include laboratory testing of three variations of soil composites consisting of fly ash, bentonite, and coconut fiber. Each variation was tested through swelling test, Standard Proctor, permeability test, and desiccation crack test simulated in temperature-controlled compaction tanks (25°C and 40°C) for 15 days. Visual and quantitative analyses of CIF were performed by periodic im-aging and processing using MATLAB software. Results showed that the composite with the highest bentonite content (V1) showed the largest CIF value (2.94% at 40°C and 0.38% at 25°C), while the composite without bentonite (V3) had the lowest CIF value (0.138% at 40°C and 0% at 25°C). In summation, material adding with bentonite and coconut fiber can decrease the desiccation crack significantly due to elasticities modulus, to absorb deformation before spreading the crack. Furthermore, the use of wetting-drying cycle as a method and measured by CIF to analyse the morphology crack are beneficial to assess the variation sample.

ObjectiveTo evaluate the clinical performance of nitric acid associated with a mineral-enriched adhesive system compared to the conventional approach of phosphoric acid and a universal adhesive in cervical carious lesion restorations.Materials and methodsTwenty-six individuals with 44 cervical anterior carious lesions were randomized into two equal parallel groups. The intervention group received a nitric acid etch (Clean and Boost dentin enamel cleanser, Vista Apex, USA) in conjunction with a mineral-enriched adhesive and a flowable composite liner (RE-GEN, Vista Apex, USA). Control group treated with phosphoric acid (Scotchbond Universal Etchant, 3 M ESPE), a universal adhesive (Single Bond Universal Adhesive, 3 M ESPE), and a standard liner (Filtek Supreme, 3 M ESPE). All cavities were restored using nanohybrid resin composite (Filtek Z350XT, 3 M ESPE). Postoperative sensitivity was assessed both qualitatively, using the modified USPHS criteria, and quantitatively, using a visual analog scale (VAS), as the primary outcome. In addition, clinical performance regarding marginal discoloration, adaptation, secondary caries, and retention was evaluated as secondary outcomes using modified USPHS criteria. Outcomes were assessed at 24 h, 6, 12, and 18 months. The data was statistically analyzed using intention-to-treat analysis. Intergroup comparisons were performed using the Chi-Squared test with a significance level (p ≤ 0.05), and intragroup comparisons were analyzed using Cochran’s Q test with a confidence level of 95% and a study power of 80%. Relative risk was used to assess clinical significance. The survival rate was analyzed using the Kaplan-Meier and Log-rank tests. The study was conducted following the CONSORT 2025 guidelines.ResultsBoth groups demonstrated similar performance in terms of postoperative sensitivity, retention, secondary caries, and marginal adaptation, as assessed using modified USPHS criteria. However, there was a significant increase in marginal discoloration within the phosphoric acid groups after 18 months. There was 50% less risk of sensitivity with nitric acid compared to phosphoric acid using the VAS scale (CI (0.2512 to 0.9953); p = 0.0485). The tested groups showed an equal survival rate (p = 0.3771).ConclusionCombining nitric acid with a mineral-enriched system is a promising approach for restoring cervical carious lesions.

Per- and polyfluoroalkyl substances (PFAS) profiles in primary and secondary landfill leachates: Indications of transformation, liner interactions, and other PFAS sources.