High-density Polyethylene Geomembrane Research Articles

Using strain hardening to predict the stress crack resistance of unaged and aged smooth black HDPE geomembranes

The correlation between the single-point notched constant tensile load-stress crack resistance (SP-NCTL SCR) Test (ASTM D5397; Appendix) of smooth high density polyethylene (HDPE) geomembranes and their strain hardening modulus is investigated for both unaged and aged specimens. The strain hardening modulus was calculated based on the (force-elongation) raw data from the tensile strength test conducted at room temperature using Type IV and/or Type V specimens (as described in ASTM D638) at a test speed of 7 mm/min. Three different approaches are used to define the strain hardening modulus and to compare the representative strain hardening modulus with the SP-NCTL SCR. It is shown that the high test speed of 7 mm/min performed at room temperature provides a good correlation with the SP-NCTL SCR of different smooth black HDPE geomembranes. Additionally, the proposed method using Type V specimens predicts the SCR values during oxidative degradation close to those observed using the SP-NCTL SCR test. For the resins and conditions examined, the proposed method provides a quick assessment of the SP-NCTL SCR of unaged geomembranes when the SP-NCTL SCR takes long testing times (e.g., >1000 h) or in jurisdictions in which the use of surfactants becomes prohibited to allow conducting the SP-NCTL SCR tests.

Deterioration modes, mechanisms, and effects of flexible landfill facilities disposing hazardous waste

Dynamic performance and lifespan predictions are essential for understanding the whole life-cycle emissions and environmental impacts of landfills. However, there are knowledge gaps regarding the major failure modes and mechanisms in flexible hazardous waste landfills (FHWLs) and their potential effects on the service life of landfills. These issues limit the advancement of related research. In this study, focusing on flexible landfills, failure mode, mechanism, and effects analysis was conducted to identify the major failure modes, mechanisms, and impacts that may occur in landfills under extremely harsh chemical and stress conditions. The results indicate that there are approximately 33 major components and materials in landfills, corresponding to 35 potential failure modes and more than 60 underlying failure mechanisms. Notably, the failure of the drainage media in the drainage system is concerning and challenging to recover from. In contrast, the failure of the high-density polyethylene geomembrane (HDPE GMB) in the liner system (LS) is considered serious and is prone to occur, but it is also difficult to detect. Therefore, these two failure modes were identified as critical factors affecting the degradation of the performance and longevity of FHWLs. Finally, due to their high probability of occurrence and severe impacts, stress damage (physical damage) and oxidative aging were identified as the main degradation modes of HDPE GMB, the core material in FHWLs. This study provides key insights into performance prediction targets, failure modes, and failure mechanisms for further research on long-term landfill performance and life prediction. It prompts the government and stakeholders to re-examine the rationality behind the positioning of landfills, such as the assumptions of unlimited service and solid waste management endpoints. Therefore, it calls for a reassessment and optimization of the full life cycle emissions of landfills and related waste.

Long-term performance of HDPE extrusion Welds aged at 85°C in synthetic leachate

The effect of ageing at 85°C of extrusion welds of 1.5 mm-thick high-density polyethylene (HDPE) geomembrane, immersed in synthetic municipal solid waste leachate, is investigated with respect to its standard oxidative induction time (Std-OIT) and stress crack resistance (SCR). Results show that the heat-affected zones (HAZ) adjacent to the squeeze-out bead (flashing) may exhibit faster STD-OIT depletion than the sheet. Generally, individual weld SCR failure times were observed to be between that of the notched and unnotched sheet. Welds with high welding-induced geometric irregularities (WIGI), and overheated fusion and extrusion welds are shown to result in SCR failure times close to that of a notched sheet during immersion time. The average time to nominal failure (taken to be when tNF =250 hours) of Cool and Good welding parameter combinations ranges between 3% and 15% shorter than the unnotched sheet. Differences in tNF were attributed to accelerated craze formation in welds with high WIGI from stress concentration. No significant difference was observed between the SCR values of fusion and extrusion welds during 40 months of immersion in MSW-L3. This paper shows that overgrind negatively impacts the SCR of welds and accelerates the degradation of SCR.

Effect of geomembrane liner on landfill stability under long-term loading: interfacial shear test and numerical simulation.

Clay liners have been widely used in landfill engineering. However, large-scale clay excavation causes secondary environmental damage. This study investigates the feasibility of replacing clay liners with high-density polyethylene (HDPE) geomembranes with different specifications and parameters. Laboratory interface shear tests between municipal solid waste (MSW) samples of different ages and geomembranes were conducted to study the influence of landfill age on interface shear strength. Finite element method was adopted to compare the long-term stability of landfills with HDPE geomembrane versus clay as intermediate liner. The interfacial shear test results show that the cohesion of MSW increases in a short term and then decreases with landfill age. The internal friction angle exhibits an increasing trend with advancing age, however, the rate of its increment declines withage.The rough accuracy of the film surface can increase the interfacial shear strength between MSW. The simulation results show that, unlike clay-lined landfills, the sliding surface of geomembrane-lined landfills is discontinuous at the lining interface, which can delay the penetration of slip surfaces and block the formation of slip zone in the landfill. In addition, the maximum displacement of landfills with geomembrane is 10% lower than that with clay, and the absolute displacement of slope toe decreases with the increase of roughness at the interface of geomembrane. Compared with clay-lined landfills, the overall stability safety factor increased by 18.5-30%. This study provides references for landfill design and on-site stability evaluation, contributing to enhanced long-term stability.

Investigations on the seepage characteristics of polymer grouting body for repairing HDPE geomembrane defects based on LF NMR

As high-density polyethylene (HDPE) geomembranes in landfill liner systems increasingly age and damage, seepage incidents frequently occur and severely threaten the surrounding ecological environment and groundwater safety. Targeted injection grouting with polymer materials can rapidly restore the barrier function by repairing defects in damaged geomembranes. To investigate the sealing mechanisms of polymer grouting bodies with various densities, this study used low-field nuclear magnetic resonance (LF NMR) techniques to monitor and visualize the permeation process within the grouting bodies. The results revealed two failure modes of the grouting bodies under water flows: 1) insufficient interfacial shear strength between the low-density polymer and geomembrane, leading to interfacial leakage; 2) gradual buildup of permeation pressure puncturing the foam cells of the polymer matrix and inducing permeation channels. Selecting polymers with suitable expansion ratios to produce appropriate expansive pressures is crucial to enhance interfacial shear strength while avoiding secondary damages to geomembranes. Increasing the density of the polymer grouting body can also enhance the compressive strength of foam cells and interfacial shear resistance. These are crucial for enabling grouting repair of defects in geomembranes and improving their barrier performance.

Effect of welding parameters on properties of HDPE geomembrane extrusion welds

The stress crack resistance (SCR) of high-density polyethylene (HDPE) geomembrane extrusion welds is examined for a 1.5 mm HDPE geomembrane and three different welding parameter combinations (denoted as “Cool”, “Good”, and “Overheated”). Results are reported for unnotched welds, unnotched sheet, and notched sheet. The average SCR for a Good extrusion weld is 23% of that of the unnotched sheet SCR. Little variation is found between the three welding parameter combinations for low geometry irregularity SCR weld specimens. There is no statistically significant difference between a good-quality fusion and extrusion weld. However, operator-dependent weld induced geometric irregularity (WIGI) greatly affects the SCR of extrusion welds. Extrusion welds with high WIGI have an average unnotched SCR of only 9% of the unnotched sheet. Extrusion welds with an overground surface can have an unnotched SCR as little as 1% of the best extrusion weld. Deleterious weld bead geometries are identified to provide a framework with which engineers can identify “high-risk” extrusion welds with respect to stress cracking.

Experimental study on the effect of temperature on HDPE geomembrane/geotextile interface shear characteristics

Geomembranes (GMBs) and geotextiles (GTXs) are the most widely used geosynthetics in landfills and other barrier systems. While various temperature environments may be encountered in practice, the interface shear characteristics of geosynthetics under different temperatures are still not clear. Shear tests of the interface between a high-density polyethylene GMB and nonwoven GTX are performed using a temperature-controlled submerged direct shear apparatus. The testing temperatures range from 10 °C to 70 °C, which covers most of the situations commonly encountered in engineering. The shear behaviors of the textured GMB/GTX interface and smooth GMB/GTX interface are presented, and the mechanism of the temperature influence is analyzed according to the test results and phenomena. Temperature has a significant impact on the GMB/GTX interface peak strength and post-peak strength, and maximum interface shear strength could be obtained when the temperature is approximately 30–40 °C. The influencing mechanisms of temperature on the GMB/GTX interface shear strength are thoroughly discussed. The shear characteristics of the GMB/GTX interface under different temperatures are critical to the stability analysis of geosynthetic slopes in special condition, and this study can also provide a reference for the effect of temperature on the shear behavior of other geosynthetics.

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.

Seepage Analysis and Optimization of Reservoir Earthen Embankment with Double Textured HDPE Geo-Membrane Barrier

This research paper focuses on conducting a steady state seepage analysis along with the downstream slope factor of safety using the Modified Bishops method in a poorly compacted earthen embankment and optimizing the same reservoir earthen embankment in a case study located near Sadiyavav village in Junagadh district in Gujarat, India. The study site, situated at 21°32'06.5"N and 70°37'26.7"E, is renowned for its Asiatic lions. The analysis and optimization were performed with a double-textured High-Density Polyethylene (HDPE) Geo-membrane barrier. Previously, designs and numerical solutions proposed homogenous embankments and too poorly compacted with no drainage arrangements, which led to anisotropic conditions within the section and water seeping out, cutting the phreatic line. The paper presents the documented improvements in the factor of safety achieved through the seepage analysis and the optimization of the HDPE Geo-membrane barrier. Two improvement techniques were studied using the “Limiting Equilibrium-Finite Element Method” (LS-FEM). The first using (HDPE) Geo-membrane stabilized with gabions, and the second alternative using HDPE Geo-membrane with gabions in addition to rock toe. The study results showed improvements in the downstream slope stability for the two alternatives by 3% and 10%, respectively. Doi: 10.28991/CEJ-2023-09-11-07 Full Text: PDF

Assessment of the interface shear strength between HDPE geomembrane and tropical soil by the direct shear test

Liners are important impermeable constituents of sanitary landfill to contain the transport of pollutants to the unsaturated zone. The system can be made of different kind, being the compacted soil and geosynthetics widely used. Thus, knowing the interface shear strength of those materials is important to avoid rupturing the system. The purpose of this paper is to compare the shear strength in the geomembrane-soil interfaces by the direct shear test. Assays were performed under the dry and saturated condition (water and leachate). The used soil is a colluvial, lateritic, tropical silty sand-clay, typical of the city of Campinas, in Brazil. In this work, high density polyethylene (HDPE) 2,00mm geomembrane, smooth and two texturized – with different roughness level - were used. It was found that the shear strength is directly influenced by the roughness of the geomembrane, showed higher friction angle in the textured geomembrane. The direct shear test, performed with soil contaminated by leachate showed smaller friction angle than uncontaminated soil.

Transport of Organic Contaminants in Composite Vertical Cut-Off Wall with Defective HDPE Geomembrane.

Soil-bentonite vertical cut-off wall is an emergency technique used for contaminant control in geo-environmental engineering, high-density polyethylene (HDPE) geomembrane (GM) with an extremely low-permeability coefficient is expected to enhance the contaminant barrier effect of the vertical cut-off wall. To evaluate the barrier performance of the composite barrier composed of GM and soil-bentonite mixture towards organic contaminant, while also quantitively revealing the impact of GM defects and placement, a one-dimensional transport model for organic contaminants in composite barrier is solved under semi-infinite boundary conditions. The proposed transport model is validated by numerical simulations using COMSOL Multiphysics 5.4, and the effects of GM defect rate, placement within the composite isolation wall, and contact level with soil-bentonite on contaminant transport behavior are further studied. The results show that as the average frequency of GM defects increases from 2.5 to 50 holes per hectare, the breakthrough time of organic contaminants through composite barrier decreases by almost 70%. Poor contact level between GM and soil-bentonite mixture may reduce the breakthrough time of the composite cut-off wall by 65%. Although the selection of GM placement has limited impact on the transient flux of contaminants, it does affect the total flux of contaminants over a certain period of time. The effects of permeability coefficient, effective diffusion coefficient, distribution coefficient, and hydraulic head of the composite cut-off wall can be considered by the proposed analytical solution, which would provide guidance and reference for the design and service performance evaluation of the composite cut-off wall.

Introduction of cow manure biogas using the HDPE geomembrane model in Pinogu, Gorontalo

Pinogu sub-district is an organic area in Bone Bolango district, Gorontalo province with abundant cattle potential. Behind a large number of cows in the Pinogu area, a new problem arises in the form of cow manure scattered on the streets. One of the technologies developed to overcome this problem is the introduction of biogas as a solution for utilizing cow manure which is environmentally friendly renewable energy. The digester model produced is a tubular HDPE (high-density polyethylene) geomembrane that has the advantages of being cheap, durable, and suitable for construction in the Pinogu area which has shallow groundwater characteristics. The process of constructing the digester was carried out for 10 days at the house of a resident in Pinogu Induk Village with the stages of site survey, design of the biogas installation unit, introduction, and training on constructing the digester to test the flame. Gas can be used after 5 days of filling cow dung into the digester. In addition to biogas, the remaining results of fermentation and degradation of cow dung can be used as liquid or solid organic fertilizer. It is hoped that with the construction of the HDPE geomembrane model biogas, the community will be able to take advantage of the potential of cow dung as an alternative fuel or renewable energy that is environmentally friendly.

Degradation of HDPE, LLDPE, and blended polyethylene geomembranes in extremely low and high pH mining solutions at 85 °C

The durability of five 1.5-mm thick geomembranes (GMBs) is investigated in pH 0.5 and 13.5 synthetic mining solutions using immersion tests. Two high density polyethylene (HDPE), two linear low density polyethylene (LLDPE), and one blended polyethylene (BPO) GMBs are investigated at 85 °C for incubation durations of 4.5–6.5 years. It is shown that the degradation of all five GMBs in the high pH solution is faster than in the low pH solution. In the pH 0.5 solution, one of the HDPEs and the BPO GMBs exhibited polymer degradation before or at the time of the depletion of their antioxidants. In pH 13.5, four out of the five GMBs exhibited degradation and followed the conceptual three-stage degradation model until nominal failure. However, there is no correlation between the long-term performance of these GMBs and their resin type or their initial properties since one of the examined LLDPEs outperformed all the higher density/crystallinity GMBs with higher initial properties while the other LLDPE did not perform well. Thus, when selecting a GMB for a desired application, the relative performance of different candidate GMBs can be only assessed using immersion tests using the solutions expected in the field.

A Copula-Based Meta-Stochastic Frontier Analysis for Comparing Traditional and HDPE Geomembranes Technology in Sea Salt Farming among Farmers in Phetchaburi, Thailand

This study analyzed sea salt production and compared the technical efficiency level and the technology gap between traditional technology and High-Density Polyethylene Geomembranes (HDPE GMB) technology in the Phetchaburi province using a copula-based meta-stochastic frontier technique. A total sample size of 250 was chosen, comprising 195 traditional farmers and 55 HDPE GMBs farmers. Several copula families were used to analyze the dependence structure of the two error components and the best-fit copula-based meta-frontier model used Gaussian copulas. Land, labor, and fuel energy are the most significant input variables in the Gaussian copula-based meta-frontier model with a translog production function. Compared to meta-frontier production, the average technological gap between traditional technology production and HDPE GMB technology production was 0.69 and 0.77, respectively, meaning HDPE GMB technology is more technically efficient than traditional technology. The study identified that land, market price, sex, and experience were the contributing technical inefficiency factors for traditional technology production. For HDPE GMB technology production, land, sex, and experience were found to be contributing factors. The performance of HDPE GMB technology in salt farming in the Phetchaburi province suggests that public and private sector agencies should promote greater access to this technology for salt farmers.

Mathematical approach of the design and fabrication of a HDPE geomembrane biodigester for the recycling of biodegradable waste into biogas and organic liquid fertilizer

The purpose of this work is to design a biodigester with high density polyethylene (HDPE) geomembrane material which will be effective in recycling biodegradable waste and produces both biogas and organic liquid fertilizer. A tubular trapezoidal biodigester is designed, following by the fabrication of a 300 litter’s prototype biodigester with a tarpaulin. After running air and water tightness of the system, quantified biodegradable waste are introduced with and observed for a period of 60 days. Several tests are then conducted on the biodigester to ensure that the system can support the load it will be subjected under normal functioning condition. These tests included shear test, peel test, and air tightness of the system. In order to predict the quantities of elements that can be produce by the biodigester, the nonlinear differential equations of the exchange inside the biodigester are written and solved by using the differential transformed method. Results obtained from the prototype and the HDPE geomembrane biodigester shows that, this design permits the recycle of biodegradable waste from any facility. The biogas obtained was proven to be rich in methane content and the organic liquid fertilizer was also rich in N-P-K fulfilling the basic requirement for plant healthy growth. The HDPE geomembrane biodigester could produce 1,250L of biogas daily at an approximate pressure 1.8 bars which can be approximated to 5 hours minimum bu4rning with a burner of 200L/h.

Effects of perfluoroalkyl substances (PFAS) on antioxidant depletion from a high-density polyethylene geomembrane

To safely contain Per-and Polyfluoroalkyl substances (PFAS) in municipal solid waste landfills and contaminated soil monofills, it is necessary to understand how these substances interact with components of engineered systems designed to contain them. This paper examines the interaction between one of the most critical components of the system: a high-density polyethylene (HDPE) geomembrane. The same geomembrane is immersed in PFAS solution and synthetic municipal solid waste leachate containing PFAS for 2.5 years, and the effects of PFAS on antioxidant depletion time is examined. The geomembrane is incubated in ovens at 85-40 °C to obtain data for Arrhenius predictions at typical landfill temperatures. When exposed to PFAS solution alone, the antioxidant depletion times are smaller than when the same geomembrane is immersed in synthetic municipal solid waste leachate alone. The combination of the two has a synergistic effect which leads to an even greater reduction in antioxidant depletion time for this geomembrane, with results showing a 68% decrease in predicted antioxidant depletion time at a typical landfill temperature of 35 °C when PFAS is present in leachate. This study highlights the need to consider the potential impact of PFAS on the service life of geomembranes used to contain them.

Coupled effect of UV ageing and temperature on the diffusive transport of aqueous, vapour and gaseous phase organic contaminants through HDPE geomembrane

High-density polyethylene geomembranes (HDPE GMBs) are indispensable in constructing composite barriers of modern engineered landfills. GBMs would be exposed to various weathering conditions apart from the interaction of organic pollutants in landfill gas and leachate. Though many studies have investigated the contaminant's migration, the transport of volatile organic compounds (VOCs) concerning the synergistic effect of thermal and UV exposure has not been thoroughly explored. Given this, the present study investigated the diffusive transport of four VOCs (aqueous and vapour phase) at 10 °C, 25 °C, 40 °C, and methane diffusion through an HDPE GMB subjected to accelerated UV weathering. The results indicated that the contaminant phase (aqueous, vapour, gaseous), its properties (aqueous solubility, molar mass, polarity), temperature, and the extent of ageing significantly influenced the transport behaviour. The standard oxidative induction time decreased appreciably with ageing duration following a first-order exponential decay. The change in tensile properties and melt flow index indicated the dominance of UV degradation by cross-linking, resulting in an increased crystallinity of GMB that was identified using Fourier transforms infrared (FTIR) spectroscopy and Differential scanning calorimeter (DSC). The crystallinity increased with UV ageing and caused the sorption and diffusion coefficients to decrease.

Importance of thickness reduction and squeeze-out Std-OIT loss for HDPE geomembrane fusion seams

The difference in seam squeeze-out antioxidant loss (in terms of standard oxidative induction time, Std-OIT loss) and thickness reduction are evaluated for three different 1.5 mm-thick high density polyethylene (HDPE) geomembranes (GMBs) seamed using a variety of welding parameters and two different wedge welders. Partial squeeze-out antioxidant loss was detected in seams created from each of the three materials examined, with the majority off loss occurring when seam thickness reductions fell between 0.4 mm and 0.8 mm. Seams with thickness reduction exceeding 0.8 mm were found to exhibit greater squeeze-out Std-OIT loss, with near full Std-OIT depletion for one material. Wedge welder size was found to influence this relationship, some seams created with the large wedge welder exhibiting a near full Std-OIT depletion from squeeze-out at approximately 0.6 mm thickness reduction. Variation in seaming pressure and high load melt index (HLMI) were found to shift the degree of thickness reduction a seam may experience for a given welding speed and temperature, with higher seaming pressure and HLMI values generally resulting in greater thickness reduction. Although, for a given welding speed, wedge temperature, and sheet temperature combination, changes in seaming pressure had a limited effect on squeeze-out Std-OIT loss. This paper provides a rational basis into defining a practical 1.5 mm fusion seam thickness reduction criteria based on limiting antioxidant loss within a seam's squeeze-out and also provides a framework for identifying potentially higher risk fusion seams for future research.

Factors affecting multicomponent GCL-geomembrane interface transmissivity for landfills

A series of laboratory tests were conducted to investigate the interface transmissivity, θ, between a 1.5 mm thick high-density polyethylene geomembrane (GMB) and a multicomponent geosynthetic clay liner (GCL) when permeated with a simulated municipal solid waste landfill leachate under a range of applied stresses (10–150 kPa). The effect of three different prehydration fluids, a 4 mm diameter central coating defect, coating defect position, and the effect of coating orientation of the GCL were investigated. It was found that at an applied stress of less than 70 kPa, the effect of these factors on θ was largely masked by the variability in the initial interface contact condition between the GMB and GCL. At 100–150 kPa, the effects of initial variability were largely eliminated, but there was no notable effect of other factors for multicomponent GCLs on interface transmissivity.

Long-term stress crack resistance of HDPE fusion seams aged at 85 °C in synthetic leachate

The stress crack resistance (SCR) and standard oxidative induction time (Std-OIT) reduction of high- density polyethylene (HDPE) geomembrane (GMB) fusion seams is examined for a 12-year old 1.5 mm HDPE GMB when welded using nine welding parameter combinations. The GMB experienced a decrease in Std-OIT from 135 to 87 min between manufacturing and welding. Welding did not significantly decrease the Std-OIT in the heat-affected zone (HAZs). In general, individual seam SCR failure times fell between the notched and unnotched sheet, with adhered squeeze-out bead seams exhibiting individual failure times closer to the notched sheet and an average time until nominal failure ( tNF) ∼21%–35% shorter than the unnotched sheet. Differences in tNF are attributed to residual stresses and (or) accelerated craze formation in seams with adhered squeeze-out beads. Non-adhered squeeze-out seams exhibited a slower tNF similar to that of the unnotched sheet, indicating a seam tNF less than that of the sheet may not be intrinsic to all HDPE fusion seams. High sheet temperatures at the time of welding and higher heat-applied welding parameters are thought to increase the likelihood of squeeze-out bead adherence. This paper shows that squeeze-out adherence can have a deleterious effect on seam SCR.