Landfill Liner Research Articles

Using viscosity as an index for polymer loading of bentonite-polymer composite geosynthetic clay liners

Bentonite-polymer composite (BPC) geosynthetic clay liners (GCLs) containing a mixture of air-dry granules of bentonite and polymer have been developed for containment of wastes that generate leachates that are too aggressive for conventional sodium bentonite GCLs. Sufficient polymer loading is essential for BPC GCLs to maintain low hydraulic conductivity, and expedient methods are needed for manufacturing quality control and construction quality control to confirm that BPC GCLs contain sufficient polymer. In this study, a methodology for developed to estimate the polymer loading based on viscosity testing of slurries prepared with the BPC. A simplified version of the method can be used to determine if polymer is present in a BPC. Factors influencing the viscosity measurement were evaluated systematically, including water-to-BPC ratio, tempering time, and mixing method. The method that was developed consists of (1) adding deionized water to dry BPCs to achieve a water-to-BPC ratio of 30, (2) blending the BPC-water mixture with an overhead stirrer at 5000 rpm for 30 min to create a homogeneous slurry, (3) tempering the slurry in a zip-top bag for 24 hr, and (4) measuring the viscosity of the slurry in a viscometer at 300 and 600 rpm. Linear relationships were developed between polymer loading and viscosity for two BPC GCLs. Independent validation confirmed that the polymer loading estimated with the method is ±0.25% of the actual polymer loading.

Petrophysical Relationship between Soil Moisture Content and Dielectric Permittivity for Wastewater Landfill Contaminated in Cherang Hangus Soil Using GPR

This study focuses on the dielectric permittivity of Cherang Hangus soil, a laterite type known for its water retention and landfill liner applications. By leveraging GPR data alongside empirical models, researchers aim to understand how moisture content influences dielectric permittivity, which is critical for managing wastewater migration in various soil types. The methodology involves simulating landfill conditions using a concrete tank filled with Cherang Hangus soil and solid waste, allowing for detailed monitoring of moisture and GPR scans. The study employs various regression models to predict dielectric permittivity based on moisture content, including linear, logarithmic, and polynomial approaches. Results indicate that more complex models, particularly the third-order polynomial, provide better accuracy in capturing the relationship between moisture content and dielectric permittivity, as evidenced by high R² 0.9883 for 3rd order regression model for Cherang Hangus. The findings underscore the significance of soil composition in predicting dielectric permittivity, highlighting that the high gravel content in Cherang Hangus soil affects moisture retention and, consequently, the accuracy of empirical models.

Sustainable Landfill Liner Using Local Soils and Wastes Amended with Bentonite: Hydraulic Conductivity and Stochastic Leachate Transport Modeling

Sustainable Landfill Liner Using Local Soils and Wastes Amended with Bentonite: Hydraulic Conductivity and Stochastic Leachate Transport Modeling

Using EPS and CFRP liner to strengthen prestressed concrete cylinder pipe

The prestressed concrete cylinder pipe (PCCP) with broken wires should be strengthened to maintain the safe operation of the pipeline. A new reinforcement technology is proposed in this study: expanded polystyrene (EPS) + carbon fiber reinforced polymer (CFRP) liner. The innovative method allows CFRP to bear the internal pressure prior to PCCP, greatly improving the reinforcement effect of the pipe. A three-dimensional finite element model is established and assessed by the experimental results. Then, the mechanical properties of the PCCP when subjected to different pressures and wire breakage are analyzed under three conditions (i.e. no strengthen, strengthened by only CFRP liner, and strengthened by EPS+CFRP liner). And the improvement effect of the innovative technology on the PCCP's bearing capacity compared with the traditional method is studied. The results showed that when repaired by 8-layer CFRP liner only and EPS and 6-layer CFRP composite liner, the internal pressure bearing capacity of PCCP can be increased by 9.17% and 50.83%, respectively. Based on the elastic limit state of the pipe, the wire breakage threshold of PCCP is 65 and 89 under the cases of no repair and CFRP liner repair. For the case of EPS + CFRP liner repair, when the number of broken wires is 100, the steel cylinder does not yield.

Transport of per-polyfluoroalkyl substances (PFAS) in high-density polyethylene (HDPE) geomembrane liners

The objective of this study is to investigate the fate and transport of per-polyfluoroalkyl substances (PFAS) through a high-density polyethylene (HDPE) geomembrane (GM) that is commonly used in landfill composite liner systems. Tests were conducted to measure the sorption and diffusion of four per-polyfluoroalkyl substances (PFAS) with varying numbers of carbons in chain and functional groups on HDPE GM. Perfluoroalkyl carboxyl acids (PFCAs), and perfluoroalkyl sulphonic acids (PFSAs) were investigated in this study. The partition coefficients (Kd) on HDPE GM ranged from 5 to 12 L/Kg. Kd showed an increasing trend with chain length and were found to be sensitive to functional groups of PFAS. Molecular weight directly affected the Kd. The diffusion coefficients (Dg) of PFCAs and PFSAs through 0.1-mm HDPE GM were found to be in the orders of 10-18 to 10-17 m2/s. The Dg decreased with increasing molar mass and were also observed to be dependent on the functional group. Dg of PFSAs was lower than that of PFCAs for a similar number of carbons in the chain.

Influence of temperature and stress in the transmissivity of GCD used in landfills

Twenty-one transmissivity tests were performed in a double composite liner contaminant barrier for landfills. The secondary drainage system was tested with three geocomposite drains with different geonet core structures, biplanar, triplanar, and triaxial. Half of the tests were conducted under normal applied load of 250 kPa and varying temperatures of 30, 65, 75 and 85oC, to simulate different temperatures commonly found in the liner. The other half was performed at 30oC and varying applied stresses of 50, 150, 250 and 350 kPa, to simulate different heights of waste on top of the liner. The triaxial and triplanar GCDs presented similar but higher than the biplanar, rate of decrease in the flow rate with increasing temperature at 250 kPa. The highest the temperature of the liner, the smallest the flow rate of the geocomposite drain, but with a faster rate between 30-65oC than between 65-85oC.

Sustainable adsorption of methylene blue onto biochar-based adsorbents derived from oil palm empty fruit branch: Performance and reusability analysis

This study examines methylene blue (MeB) adsorption by biochar-based adsorbents made from oil palm empty fruit branches. Untreated biochar (BC) and treated activated carbons 1BT and 2BT for one- and two-step KOH treatments were analyzed using FTIR, XRD, SEM-EDX, and BET to determine their physical, chemical properties and adsorption reusability. Adsorption experiments fitted pseudo-second order kinetics which fit experimental data satisfactorily. Langmuir isotherm has the best fitting data, showing monolayer adsorption, moreover three-parameter models like Redlich-Peterson, Sips, and Toth also match well, confirming its trustworthiness. BC, 1BT, and 2BT have maximal adsorption capacities of 796.17–820.12 mg/g, 943.46–969.85 mg/g, and 1123.57–1153.72 mg/g, respectively. In addition, adsorbent reusability demonstrates gradual decreases in adsorption efficiency, and consistently remained high at 46.05 %, 48.99 %, and 48.15 % over five consecutive reuse cycles for BC, 1BT, and 2BT, respectively. These findings have significant implications for the practical application as additive materials in modern landfill liner.

Evaluating the Potential of Multi-Walled Carbon Nanotube-Modified Clay as a Landfill Liner Material.

In this paper, the feasibility of multi-walled carbon nanotube (MWCNT)-modified clay as a landfill liner material is investigated. Experiments were conducted on the modified clay with 0.5%, 1%, and 2% MWCNTs. The effects of the MWCNTs on the compaction characteristics, permeability coefficient, stress-strain curve, peak deviation stress, shear strength parameters (internal friction angle and cohesion), microstructures, and adsorption performance of the clay were analyzed. The results showed that the optimum moisture content (OMC) increased from 16.15% to 18.89%, and the maximum dry density (MDD) decreased from 1.79 g/cm3 to 1.72 g/cm3 with the increase in MWCNTs. The permeability coefficients firstly fell and then gradually rose as the MWCNTs increased; the minimum permeability coefficient was 8.62 × 10-9 cm/s. The MWCNTs can also effectively increase the peak deviation stress of the clay, and at the maximum level, the peak deviation stress was increased by 286%. SEM images were processed using the Pore and Crack Analysis System (PCAS), and the results showed that the appropriate amount of MWCNTs could fill the pores and strengthen the clay structure. The effect of the MWCNT-modified clay on the adsorption performance of common heavy metal ions Cd2+, Mn2+ and Cu2+ in landfill leachate was analyzed by batch adsorption tests. The maximum adsorption capacities (Qmax) of Cu2+, Cd2+ and Mn2+ in the 2% MWCNT-modified clay were, respectively, 41.67 mg/g, 18.69 mg/g, and 4.97 mg/g. Compared with the clay samples without MWCNTs, the adsorption properties of Cu2+, Cd2+, and Mn2+ were increased by 228%, 124%, and 202%, respectively. Overall, the results suggest that MWCNT-modified clays have the potential to be suitable barrier materials for the construction of landfills.

Highlighting the use of end-of-life tire (ELT) as a renewable material and the potential applications in Indonesia

The development of the number of vehicles impacts the increased waste of used tires produced. This paper was created to explore the reuse end of life tires (ELT) as a renewable material. This paper also discusses the potential implementation of tire fiber recycling in Indonesia. Data were taken from various relevant articles from accredited sites such as Elsevier, Springer, Scopus, and Research gate. The data were reviewed using the narrative analysis method. Two recycling sectors, namely geotechnical application (Landfill liner) and civil engineering application (asphalt, pavement, LVL board, and lightweight aggregate concrete). The result shows the potential for ELT applications in Indonesia is very high. This is due to the large number of used tires in Indonesia because of the high consumption of vehicles by the population. The new recycling process carried out in Indonesia is only asphalt and pavement. There is no use of ELT for landfill liners, LVL, and lightweight aggregate concrete in Indonesia. The utilization of ELT can be maximized in Indonesia with the help of local government and research studies to reduce ELT waste in Indonesia.

Experimental Investigation of Red Soil Blended With Bentonite and Lime as a Landfill Liner

To control the migration of contaminants generated from the leachate, the liners are used in landfills. Compacted clay liners are widely used as liner materials due to the low value of hydraulic conductivity and large attenuation capacity. In the present work, an experimental study on red soil which is locally available is amended with bentonite use as a liner material for efficient leachate containment in landfills. The primary objective of this work is to determine the geotechnical properties of red soil blended with bentonite as a material for liners. The clay liners performance primarily depends on hydraulic conductivity. The hydraulic conductivity of the red soil is higher than the recommended limit (i.e.>10-7cm/s). Commercially available bentonite was blended with red soil to decrease the hydraulic conductivity. The permeability tests and falling head tests were conducted on 5%, 10%, 15%, and 20% bentonite by weight blended with red soil to evaluate hydraulic conductivity. From the experimental studies, it is clear that the red soil blended with 15% bentonite has a hydraulic conductivity value less than the requirements of landfill clay liner(i.e.<10-7cm/s). However, the Compressive Strength (CS) of blended red soil with 15% bentonite was less than 200 kPa, which is less than the minimum CS required for liner material. Lime was added to enhance the CS of the soil mixture and further studies were carried out. Swelling behavior is the major problem that is to be addressed during and after the construction of landfills. This study also presents the swelling behavior of red soil blended with bentonite and other additives.

Sorption and diffusion of per-polyfluoroalkyl substances (PFAS) in high-density polyethylene geomembranes

The objective of this study is to investigate the fate and transport of per-polyfluoroalkyl substances (PFAS) through a high-density polyethylene (HDPE) geomembrane (GM) that is commonly used in landfill composite liner systems. Tests were conducted to measure the sorption and diffusion of per-polyfluoroalkyl substances (PFAS) with varying number of carbons in chain and functional groups on HDPE GM. Perfluoroalkyl carboxyl acids (PFCAs), perfluoroalkyl sulphonic acids (PFSAs), alkyl-sulfonamidoacetic acids (FOSAAs), fluorotelomer sulfonic acids (FtSAs), alkane sulfonamides (FOSA) and ether carboxylic acids (Gen X) were investigated in this study. The partition coefficients (Kd) on HDPE GM ranged from 3.8 to 98.3 L/kg. PFAS with amide and sulfonic functional groups showed stronger sorption than that of PFAS with carboxylic acid functional groups. Molecular weight directly affected the Kd for long-chained PFAS whereas the Kd of short-chained PFAS was not sensitive to molecular weight. The diffusion coefficients (Dg) of PFCAs and PFSAs through 0.1-mm HDPE GM were found to be in the orders of 10-18 to 10-17 m2/s. The Dg decreased with increasing molar mass and were also observed to be dependent on the functional group. Dg of PFSAs was lower than that of PFCAs for similar number of carbons in the chain. The estimated mass flux for PFAS in an intact 1.5-mm HDPE GM varied from 38.7 to 2080.8 ng/m2/year whereas the estimated diffusive breakthrough time for PFAS in intact 1.5-mm HDPE was 1526 years or longer.

Enhancing the performance of HTPB‐IPDI‐based polyurethane composite liner through effective carbon black dispersion**

AbstractThis study aims to improve the dispersion of Carbon Black (CB) filled Hydroxyl‐Terminated Polybutadiene (HTPB)‐Isophorone Diisocyanate (IPDI) based polyurethane liner by both adding a dispersant and developing a production process to obtain improved mechanical, rheological, thermal, and adhesion properties. Printex‐U (CB1) and Thermax N‐991 (CB2) carbon blacks were used as fillers. Three different dispersants, which are BYK 9076 (D1), BYK 9077 (D2), and BYK Silclean 3700 (D3) were added to the liner formulation at various amounts. BYK 9076 (D1) was found as the most effective dispersant due to its bifunctional chemical structure. By adding 2 wt.% of BYK 9076 (D1) dispersant to the polyurethane liner comprising 10 wt.% CB1, viscosity was reduced by 45 %, and tensile strength and elongation at break were improved from 1.77 MPa to 1.88 MPa and from 375 % to 385 % respectively. The dispersion of the CB in the polyurethane liner was further improved by the ultrasonication process and tensile strength and elongation at break were increased to 2.03 MPa and 425 %, respectively. This process also contributed to an improved Limiting oxygen index (LOI), elevating it from 20 % to 22 % initially and further by 25 % through ultrasonication. Scanning Electron Microscopy (SEM) verified that the addition of D1 dispersant and ultrasonication effectively reduced CB particle agglomeration. The migration of plasticizer was also assessed over 12 months through bonding testing, TGA, and FTIR analysis. It was noticed that the effective dispersion of CB particles made the liner more resistant to the plasticizer migration.

Influence of bagasse ash on the compressive strength of lime reconstituted expansive soil by Advanced Machine Learning (AML) for sustainable subgrade and liner construction applications

The utilization of expansive soils for the construction of landfill liners and subgrade facilities without stabilization leads to volume changes due to seasonal change between wet and dry. This necessitated the industrial- and agro-industrial-based waste materials reconstitution of expansive soils to fulfil sustainability requirements for the builtenvironment. In this research paper, multiple datasets were collected from mixes of bagasse ash (BA) and lime (Lm) blend reconstituted expensive soil and deployed in the training and validation interface of advanced machine learning (AML) techniques to predict the unconfined compressive strength (UCS) of the treated soil for their usein landfill liner and subgrade application. The relative importance values for each input parameter were evaluated, such as compaction parameters (MDD and OMC), plastic limit (PL), LL, Lm, and BA. The results of all developed models were observed and collected. The relations between calculated and predicted values show that the GP produced a parametric line of fit expression of y = 0.999 × with performance indices as MAE 14.80 kPa, MSE 400.7 kPa, RMSE 20.00 kPa, and R2 of 0.950, EPR produced a parametric line of fit expression of y = 0.992 × with performance indices as MAE 11.6 kPa, MSE 270.9 kPa, RMSE 16.50 kPa, and R2 of 0.963, and ANN produced a parametric line of fit expression of y = 0.997 × with performance indices as MAE 4.26 kPa, MSE 30.8 kPa, RMSE 5.55 kPa, and R2 of 0.996. The results show that the ANN outperforms the GP and the EPR having produced the least error values, the highest coefficient of determination (R2) and zero outliers beyond the ± 25% performance fit envelop and can be concluded that BA has a remarkable influence in the stabilization of expansive soils and its utilization.

Research on leakage environmental risk assessment and risk prevention and control measures in the long-term landfill process of ultra-alkaline fly ash

In this study, we simulated the actual landfill disposal process using accelerated carbonization experiments, based on the leaching characteristics of heavy metals from “alkaline” fly ash, and used the LandSim–HELP coupling model to assess the environmental risk of the leaching. The results showed that the leaching data of “alkaline” fly ash before carbonization showed the illusion of admission to landfill with only a small amount of chemical addition or even without curing/stabilization. The leached concentrations of Zn and Cd from “alkaline” fly ash after carbonation were significantly higher. The risk assessment of the leakage of heavy metals in the case of a single artificial composite liner system showed that the exposure concentrations of Pb, Zn, and Cd in samples exceeded Standard for groundwater quality (GB/T 14848–2017) the Class III permissible limits after carbonation; exposure risk for Cd was exceeded in all samples. However, although the use of a double-layer artificial composite liner to improve the level of impermeability effectively reduced the risk of Cd leaching, so that none of the non-carcinogenic risks exceeded the standard, the carcinogenic risk of Cd in the carbonized samples exceeded the factor of 1.1–4.5 of the acceptable hazard quotient, and the contamination characteristics of the alkaline fly ash still need to be kept in view.

Permeability and Cracking of Compacted Clay Liner Improved by Nano-SiO2 and Sisal Fiber

The landfill liner is the last line of defense to protect the soil from damage, but it is difficult to satisfy both impermeability and crack resistance requirements with conventionally compacted clay. This paper proposes a new composite material to enhance the anti-seepage and anti-cracking properties of clay as a solution to this problem. In this Study, the effects of two single amendment materials, Nano-SiO2 (6 dopings) and sisal fiber (SF) (4 dopings), and a composite amendment material (Nano-SiO2+SF), on the permeability and cracking resistance of the improved clay were investigated by infiltration tests and dry-wet cycle tests, respectively. The nuclear magnetic resonance test (NMR) test reveals the microscopic pore changes of soil and explore the reinforcement mechanism. The findings of penetration experiments demonstrate that Nano-SiO2 and SF, both single and composite components, can increase the modified clay's impermeability. The optimum content of Nano-SiO2 is 3%, and its permeability coefficient is 5.09 × 10−8 cm·s−1, which is two orders of magnitude lesser than that of virgin soil. The results of three dry and wet cycle tests showed that the overall trend of fracture length and cracking factor (CIF) increased with the increase of the number of de-wetting. After the third de-wetting of the modified clay, 0.75% Nano-SiO2 + 0.3% SF is the optimal dose, which reduces the fissure length by 19.94 times and CIF by 27.25 times compared with the three de-wetting of the plain clay. As a whole, the data demonstrates that the composite Nano-SiO2 and SF are able to make up for the shortcomings of each component. It can simultaneously improve the anti-seepage and anti-cracking properties of the enhanced clay. The test results provide a certain benchmark for the impermeability and anti-cracking of landfill liners.

Geometrical modeling and experimental validation of 3D woven honeycomb fabric for lightweight aircrew helmet liner manufacturing

This research focused on the development of a honeycomb fabric by predicting the areal density suitable for aircrew helmet liner. The aim was to fulfill the requirements for the lightweight and mechanical properties of composite liner. The model was based on the structural characteristics of the preform, including the weave design and geometric parameters. The predicted areal density, based on varying yarn linear density and the number of picks in the free and bonded wall, was compared to experimental results and showed good agreement. A geometric model was derived to predict the areal density of 3D woven honeycomb preforms for producing the composite liner of aircrew helmet. The model was validated using experimental data from a variety of 3D woven honeycomb preforms, showing that it accurately predicts the areal density and can be used as a tool to design 3D woven honeycomb preforms for advanced composites.

Effect of different microcapsule types on the wear mechanism of PTFE/aramid fiber composite liners

AbstractIn this study, three different methods based on vacuum adsorption, solvent volatilization, and Pickering emulsion were utilized to prepare microcapsules with the core material of PAO40 and the wall materials of SiO2, polysulfone (PSF), and PSF/SiO2 composites, respectively. PTFE/Kevlar fabric liners were modified by PAO40/SiO2 microcapsules (PSMS), PAO40/PSF microcapsules (PPMS), and PAO40/PSF/SiO2 microcapsules (PPSMS). The effect of microcapsules based on different wall materials on the tribological properties of liners was investigated by friction and wear tester under low‐speed and heavy‐load conditions. The anti‐friction and anti‐wear mechanisms of several microcapsule types on the liners were systematically investigated. The results showed that PPMS induced the most significant enhancement in anti‐friction properties of liners when compared to pure liner resulting in a 19.4% reduction in coefficient of friction (COF). PSMS was found to reveal much better wear resistance of liners, as evidenced by 75% increase in wear rate. PSMS and PPSMS not only release lubricating oil after the break of microcapsules under the friction action to lubricate, but also generate a cavity to store abrasive debris for liner wear reduction. Nonetheless, PPMS only released the oil onto the friction surfaces for lubrication. PSF as the microcapsule wall material could not contribute to the formation and promote wear resistance of transfer films. SiO2 as a microcapsule wall material participates in the formation and enhances the wear resistance of transfer films. The findings obtained are anticipated to improve the reliability and broaden the range of applications of liners in aerospace and other industrial fields.Highlights Three microcapsules all improve the tribological properties of the liners. Anti‐friction and wear‐resisting mechanism of three microcapsules in liners. SiO2 as wall material can increase the wear resistance of transfer films. PAO40 in microcapsules has antifriction effect at the friction interface.

Assessment of a new rigid wall permeameter for the slurry like barrier materials: zeolite example

Areas vulnerable to catastrophic disasters such as hurricane, landslide and earthquake require ready and sustainable solutions for the post-pollution scenarios. Clinoptilolite type zeolite re- sources of Türkiye can serve economical and sustainable solutions as a quick response. While the studies on compacted zeolite-bentonite mixture at optimum water content for the landfill liners applications or dry zeolite-sand mixtures in permeable reactive barrier (PRB)s are com- mon, the slurry form of zeolite emplacement at subsurface reactive barriers has not received an attention by the researchers. In this context, this experimental study presents the prelimi- nary findings on one-dimensional consolidation and hydraulic conductivity tests performed on crushed zeolite samples S1 and S2 with fine contents of 33 and 84%, respectively. The results indicate that S2 has a higher compression index than S1, without a significant change in swelling index attributed to less than 4% clay contents. A self-designed rigid wall type per- meameter was used to study on reconstituted slurry like materials under the benefit of back pressure saturation without the consolidation during testing that encountered in flexible wall permeameter. Falling head – rising tail water procedure was adopted under the back pressure in between 200 and 700 kN/m2. S2 samples reconstituted under 25, 50, 100 and 200 kN/m2 show a gradual decrease in kv from 3×10-8 to 2×10-9 m/s. Previous observations on the sample of S1 revealed 8 times higher kv values under the same σv'. Since the fine content of zeolite limits kv, the proposed permeameter will be beneficial to determine the proper grain size dis- tribution of fill materials considering the barrier height and in-situ stress conditions before the environmental studies with leachate.

Geochemical Appraisal of Termite-Reworked Clay Soils from Basement Complex Terrain: Implications as Landfill Liners

Geochemical Appraisal of Termite-Reworked Clay Soils from Basement Complex Terrain: Implications as Landfill Liners

Numerical simulation of reactive composite jet penetrating concrete target

In order to allow more reactive material to enter the penetration hole when the initiation delay time of reactive material arrives, a double-layered liner structure with inner and outer liners of unequal height is designed. The outer liner is polytetrafluoroethylene/aluminum (PTFE/AL) reactive material, and the inner liner is metal material. The AUTODYN software were used to study the effects of height ratio α of the inner and outer liners and inner liner material on the reactive composite jet forming and penetrating C35 concrete target. The results show that when α varies, the composite liner forms a reactive composite jet composed of different materials at the head. When α is 4/5, the composite jet can both cause a large penetration depth on the target plate and allow more reactive material to enter the penetration hole. When the material of inner liner is titanium, almost all the reactive material follows the metal precursor penetrator into the penetration hole, which can significantly exert the combined damage effect of penetration and demolition.