High-density Polyethylene Geomembrane Research Articles

Ageing of exposed geomembranes at locations with different climatological conditions

The degradation of high-density polyethylene (HDPE) geomembranes exposed to the elements depends, inter alia, on the climatological conditions. This study investigates the degradation in the properties of HDPE geomembranes installed at two mine facilities after almost 16 years of exposure in a warm–hot climate and at a research site after 6 years of exposure in a mild–cold climate. Samples were exhumed at the field sites from different locations and the properties of the geomembrane were measured in the laboratory. The depletion of antioxidants detected by the standard oxidative induction time (Std-OIT) test for the geomembrane installed at the research site was faster on the slope than on the base; however, there was negligible difference in the depletion of antioxidants–stabilizers detected by the high-pressure oxidative induction time (HP-OIT) test between the slope and base. Under the field conditions described, the antioxidant depletion time for the exposed geomembrane installed at the research site (mild–cold climate) was inferred to be 20 to 54 years. The exposed HDPE geomembranes installed at the mine facilities (warm–hot climate) have reached the time of nominal failure based on their stress crack resistance. However, they have not ruptured under the exposure conditions even though the stress crack resistance has dropped to as low as 70 h at some locations.

Effect of High pH Found in Low-Level Radioactive Waste Leachates on the Antioxidant Depletion of a HDPE Geomembrane

AbstractAntioxidant depletion from a high-density polyethylene (HDPE) geomembrane with hindered amine light stabilizers (HALS) immersed in three different high pHs solutions is examined over a 3-year period. The three solutions had the same concentration of inorganic salts but a range of pH (9.5, 11.5, and 13.5) likely to encompass those found in low-level radioactive waste leachate and other geoenvironmental applications. Increasing the pH from 9.5 to 13.5 increased the antioxidant depletion rates detected by both standard and high-pressure oxidative induction time tests (Std-OIT and HP-OIT) and also increased the residual HP-OIT values. Arrhenius modeling is used to predict the length antioxidant depletion stage for each solution.

MSW Leachate Inorganic Ion Diffusion through Compacted Soil and HDPE Geomembrane Barrier - Laboratory Experiments and Model Validation

This paper presents the experimental and numerical results for soil contamination profiles by leachate with and without the presences of a geomembrane. Soil samples of the Rio das Ostras Landfill were assessed and examined. The batch tests were carried out with local virgin soil and with leachate. Molecular diffusion tests with and without the presences of a geomembrane were compared with the virgin soil of the sanitary landfill of Rio das Ostras (Brazil) and its leachate. The studies focused on the chloride and sodium ions. The model MPHMTP (Multi Phase Heat and Mass Transfer Program) was used in the computer simulations to estimate the diffusion coefficients through the compacted soil and geomembrane over a layer of compacted soil to forecast ion migration and predict the performance of the system in long term operation. The geomembrane used was a 2 mm of the high density polyethylene (HDPE). The results showed that the presence of the geomembrane strongly reduced the ion concentrations in the soil during the experiments carried out.

Durability of Three HDPE Geomembranes Immersed in Different Fluids at 85°C

Abstract The long-term performance of three different high-density polyethylene (HDPE) geomembranes (GMBs) is investigated at 85°C using immersion tests. By comparing the degradation behavior of the three GMBs in different synthetic leachates, it is shown that different chemical constituents in the leachate affected different stages of the degradation, with surfactant having the greatest effect on antioxidant depletion (Stage I) and salts having the greatest effect on the degradation after antioxidant depletion (Stages II and III). The magnitude of the effect of these chemical constituents differed from one GMB to another. Thus, for the purpose of comparing the relative long-term performance of the three GMBs for municipal solid waste (MSW) landfill applications, the GMBs were immersed in a synthetic leachate (Leachate A), which contained the primary constituents (i.e., salts, volatile fatty acids, surfactant, and trace metals under reduced conditions) present in the leachate from a large MSW landfill lea...

Permeation of Volatile Organic Compounds through EVOH Thin Film Membranes and Coextruded LLDPE/EVOH/LLDPE Geomembranes

Abstract Coextruded geomembranes with an inner ethylene vinyl alcohol (EVOH) layer are gaining attention as potential improved barriers to volatile organic compounds (VOCs) when used in barrier systems that would traditionally use high-density polyethylene (HDPE) geomembranes. The permeation characteristics of nine common VOCs in aqueous solutions through the EVOH layer are investigated for two thin films: a 0.015-mm-thick, 32 mol% EVOH and a 0.02-mm-thick, 44 mol% EVOH. The VOCs included aromatic hydrocarbons [benzene, toluene, ethylbenzene, and xylenes (BTEX)] and chlorinated hydrocarbons [1,2-dichloroethane (1,2-DCA), dichloromethane (DCM), trichloroethylene (TCE), and tetrachloroethylene (PCE)]. The BTEX permeation coefficients, P g , range from 1.4 × 10 − 14 to 25 × 10 − 14 m 2 ⋅ s − 1 depending on the contaminant and mol% EVOH. When a 0.02-mm-thick, 38 mol% EVOH thin film layer is coextruded with linear low-density polyethylene (LLDPE) to form a 0.53-mm-thick geomembrane, the BTEX permeation v...

Harmless Disposal Technology of Waste Drilling Fluid in Liaohe Oilfield

To reduce environmental pollution caused by waste drilling fluid , Liaohe Oilfield takes methods of sewage pit seepage control and waste drilling solidification disposal.Firstly,different impermeable material comparation has been taken , as a result , high-density polyethylene geomembrane (HDPE) was choosn as the impermeable material for sewage pit .which has features of good seepage control, good chemical stability, low price ,non-toxic and environment friendly.According to features of five different landforms in Liaohe Oilfield, corresponding seepage control programs are developed. impermeable material, implementation and measurement of sewage pit are unified and standardized.which prevent contamination of underground water caused by waste drilling fluid effectively. Finally, curing treatment of the waste drilling fluid is carried out ,forming a system engineering to meet the needs of environment protection and costs control.

Antioxidant depletion from five geomembranes of same resin but of different thicknesses immersed in leachate

The effect of thickness on the antioxidants depletion time for five high density polyethylene geomembranes (with nominal thicknesses of 0.5, 1.0, 1.5, 2.0, and 2.4 mm) immersed in synthetic leachate at six different temperatures (25, 40, 55, 70, 85 and 95 °C) is investigated. The geomembranes were manufactured from the same geomembrane resin (i.e., polymer resin, antioxidant/stabilizer package, and carbon-black batch). Four (1.0, 1.5, 2.0, and 2.4 mm) of the five geomembranes were manufactured during the same production run by changing the pulling speed of the geomembrane from the extrusion die. The depletion of antioxidants/stabilizers inferred from both standard (Std-) and high pressure (HP-) oxidative induction times (OIT)s show that increasing geomembrane thickness resulted in longer depletion times for temperatures above 40 °C but little to negligible difference in projected depletion times below 40 °C for this antioxidant package. The increase in depletion times was not proportional to the square of the geomembrane thickness as theoretically predicted if depletion was diffusion controlled and the diffusion coefficient was the same for each GMB. Thus, the depletion of antioxidants is not fully governed by diffusion and/or the GMB's diffusion coefficients are different. Regardless of the GMB thickness, the time for Std-OIT depletion was shorter than the time to residual HP-OIT above 70 °C but was longer at or below 55 °C. For example, for 2.4 mm GMB, the inferred time for Std-OIT depletion was 0.2–0.3 (at 85 °C), 2–3.5 (at 55 °C) and 9.5 (at 40 °C) times that for the HP-OIT to deplete to residual. The projected Std-OIT depletion times for 1.0 and 2.4 mm GMBs were: 2.7 and 4 years, respectively, at 60 °C; 23 and 26 years, respectively, at 40 °C; and about 330 years at 20 °C.

Service Life of a High-Density Polyethylene Geomembrane under Simulated Landfill Conditions at 85°C

AbstractThe time to rupture of a 1.5-mm-thick high-density polyethylene geomembrane aged in a typical landfill composite liner configuration is investigated under a pressure of 250 kPa at 85°C. The geomembrane was underlain with a geosynthetic clay liner and had a 560 g/m2 needle-pinched nonwoven geotextile protection layer separating it from 50 mm of drainage gravel containing leachate. Seventeen (0.6-m-diameter) tests were conducted. In addition to 9 months required to deplete antioxidants (Stage I), the tests indicated a lag period (Stage II) of 5.5 months and a time from the start of degradation to rupture (Stage III) of 20 months, giving a total inferred time to rupture of 34.5 months (2.9 years). There were up to 61 brittle ruptures per sample (i.e., >2 million cracks per hectare). The ruptures were predominately oriented in the machine direction and located (1) directly beneath a gravel contact, (2) at the side of a gravel indentation, or (3) between gravel indentations. The ruptures between gravel...

Effect of aging on the stress crack resistance of an HDPE geomembrane

The changes in the stress crack resistance, SCR (measured by the single point notched constant tensile load; ASTM D5397 – appendix) for a 1.0 mm high-density polyethylene (HDPE) geomembrane aged in synthetic leachate at six temperatures (25, 40, 55, 70, 85 and 95 °C) and in air and water at 55 °C were investigated for almost five years. There are observed changes in the SCR before the geomembrane chemically degraded (as manifest by melt index and tensile properties) and even before the antioxidants depletion at temperatures below 70 °C (as manifest by the standard and high pressure oxidative induction times). This change is attributed to morphological changes during aging that affected the inter-lamellar connections due to: (a) annealing that increased the strength of the inter-lamellar connections (over the temperature ranges examined), and (b) the proposed chain disentanglement mechanism. The annealing and chain disentanglement mechanisms have a counteracting effect on the inter-lamellar connections and hence on the SCR. Chain disentanglement dominated over the annealing effect at 25, 40, 55 and 70 °C, resulting, respectively, in a decrease in SCR to an equilibrium SCRm of 0.83, 0.65, 0.26 and 0.43 of the initial stress crack resistance of the geomembrane (SCRo). The maximum decrease in SCR is observed when the geomembrane is aged in leachate at 55 °C with the SCR decreasing to 0.26 SCRo. The SCR of the geomembrane aged in air and water at 55 °C decreased to about 0.5 SCRo, implying that the surfactant used in leachate may have enhanced the rate and the extent of chain disentanglement (i.e., decreasing the time to reach a lower SCRm) due to plasticization of the amorphous zone.

Effect of high temperatures on antioxidant depletion from different HDPE geomembranes

The effect of elevated temperatures, typically 95–115 °C, on antioxidant depletion from a high-density polyethylene (HDPE) geomembrane (GMB) incubated in air, water and synthetic leachate is examined. It is shown that the antioxidant depletion in synthetic leachate at 95–115 °C is consistent with what would be expected from Arrhenius modeling based on data from lower temperatures (25–85 °C). A similar finding is reached for incubation in air. However, when incubated in water the antioxidant depletion is more complicated. At temperatures above 100 °C a four-parameter exponential model was needed to fit oxidative induction time data that exhibited quite different early-time and later-time depletion rates. The early-time depletion rate decreases with an increase of the temperature while the later-time depletion rates follow the more typical pattern of increasing with increasing temperature. Three additional HDPE GMBs with different antioxidant packages are examined at elevated temperatures in air. The GMB with the lowest initial standard (Std) oxidative induction time (OIT) and without hindered amine light stabilizer (HALS) has the longest antioxidant depletion stage based on Std-OIT at these elevated temperatures. GMBs stabilized with HALS showed only a slight change in their high pressure OIT during the current study. It is shown also that degradation in physical properties can start at Std-OIT values above the residual OIT values.

Landfill side slope lining system performance: A comparison of field measurements and numerical modelling analyses

Low permeability engineered landfill barriers often consist of a combination of geosynthetics and mineral layers. Even though numerical modelling software is applied during the landfill design process, a lack of data about mechanical performance of landfill barriers is available to validate and calibrate those models. Instrumentation has been installed on a landfill site to monitor multilayer landfill lining system physical performance. The lining system comprises of a compacted clay layer overlaid by high density polyethylene geomembrane, geotextile and sand. Data recorded on the site includes: geosynthetic displacements (extensometers), strains (fibre optics, Demec strain gauges, extensometers) and stresses imposed on the liner (pressure cells). In addition, temperature readings were collected by a logger installed at the surface of the geomembrane, at the clay surface using pressure cell thermistors and air temperature using a thermometer. This paper presents readings collected throughout a period of three years and compares this measured performance with the corresponding numerical modelling of the lining system for stages during construction. Numerical modelling predictions of lining system behaviour during construction are comparable with the measurements when the geosynthetics are covered soon after placement, however, where the geosynthetics are left exposed to the sun for an extended period of time, in situ behaviour of the geosynthetics cannot be replicated by the numerical analysis. This study highlights the significant influence of the effect of temperature on geosynthetics displacements. A simple thermal analysis of the exposed geosynthetics is used to support the explanation for observed behaviour.

Interface Shear Damage to a HDPE Geomembrane. I: Gravelly Compacted Clay Liner

AbstractAn experimental program of large-scale direct shear tests has indicated that shear displacement of a high-density polyethylene (HDPE) geomembrane (GM) over a gravelly compacted clay liner (CCL) under moderate to high normal stress conditions can cause much greater damage to the geomembrane than static pressure alone. Essentially, no damage was observed at low normal stress. The greatest geomembrane damage occurred at high normal stress (1,658 kPa) and yielded an average of 169 holes/m2, with a maximum hole size of 23 mm. Size, angularity, and hardness of the gravel particles are also important factors with regard to potential damage. Geomembrane damage was greatly reduced when a needle-punched geosynthetic clay liner (GCL) was placed between the geomembrane and gravelly CCL, including one test conducted at very high normal stress (4,145 kPa). The findings suggest that gravelly soils should be viewed with caution for the construction of GM/CCL composite liners for landfill bottom liner systems and ...

Interface Shear Damage to a HDPE Geomembrane. II: Gravel Drainage Layer

AbstractAn experimental program of large-scale direct shear tests has indicated that shear displacement of a gravel drainage layer and nonwoven geotextile protection layer over a high-density polyethylene (HDPE) geomembrane under moderate to high normal stress conditions can cause much greater damage to the geomembrane than static pressure alone. Essentially, no damage was observed at low normal stress. The greatest damage occurred at high normal stress (1,389 kPa) using a lightweight geotextile (335 g/m2) and yielded an average of 31 holes/m2, with a maximum hole size of 29 mm. Surprisingly, geomembrane damage measured using a lightweight geotextile was greater than that measured using no geotextile due to a change in failure surface location. For the same conditions, shear-induced damage was slightly less for a geomembrane placed on a compacted sand subgrade than on a compacted clay subgrade. Interface shear strength increased significantly with decreasing geotextile mass/area due to greater out-of-plan...

Degradation behaviour of HDPE geomembranes with high and low initial high-pressure oxidative induction time

The degradation of three high density polyethylene geomembranes (GMBs) (denoted xA, xB and xC) when immersed in simulated landfill leachate at 85 °C is examined. All three GMBs met the requirements of the generic industry specification GRI-GM13 with respect to their performance properties. The large high-pressure oxidative induction time (HP-OIT) (i.e., 790 min for xB and 960 min for xC) combined with the relatively high level of trace nitrogen detected, suggest the presence of hindered amine light stabilizers (HALS) as part of the antioxidant package in these GMBs, whereas, the relatively low initial HP-OITs (i.e., 260 min) and the low level of trace nitrogen for xA, suggest the absence of HALS in xA. Although xA had the lowest initial standard Std-OIT (Std-OIT was 115, 158 and 175 min for xA, xB and xC, respectively) it exhibited the longest time to antioxidant depletion based on Std-OIT. For the three GMBs, the HP-OIT depleted following exponential decay model until reaching a residual value. xB had the slowest HP-OIT depletion (0.016 month−1) and was still depleting without reaching a residual value at the end of this study (after 46 months). xA experienced the fastest HP-OIT depletion (∼62 times faster than of xB) and reached a residual value of 78 min. For xC, HP-OIT depleted 40 times faster than for xB reaching a residual value (∼610 min) that was still higher than the HP-OIT of 400 min specified by GRI-GM13 for a new GMB. xB had the longest time to nominal failure despite having the lowest initial SCR value (330 h for xB compared to 910 and 800 h for xA and xC, respectively) and not having the highest OITs values. Although xC had a residual HP-OIT of 610 min, the SCR, melt index (MI) and tensile properties for xC had decreased to the point that xC was at nominal failure, indicating that the degradation can take place without the total depletion of antioxidants/stabilizers captured by the HP-OIT.

Short-Term Local Tensile Strains in HDPE Heap Leach Geomembranes from Coarse Overliner Materials

AbstractLocal tensile strains in a 1.5-mm-thick high-density polyethylene (HDPE) geomembrane induced from coarse overliner soil materials intended to simulate the physical conditions at the base of a heap leach mineral extraction pad under very deep burial are reported. They were obtained from physical experiments conducted in a 590-mm-diameter pressure vessel at applied vertical pressures up to 3,000 kPa for 100 h and a temperature of 21°C. An applied pressure of 3,000 kPa corresponds to a heap leach depth of around 150 m. Three different coarse-grained overliner materials placed directly above the geomembrane and a silty sand underliner beneath the geomembrane were examined. Both the grain size and grain size distribution of the overliner affected the maximum tensile strain in the geomembrane. At an applied pressure of 3,000 kPa, the largest strain of 27% recorded for the coarsest overliner tested, which had a maximum particle size of 50 mm and 20% sand, well exceeded one proposed maximum allowable stra...

Effects of blown film process on initial properties of HPDE geomembranes of different thicknesses

ABSTRACT: The differences in the properties of five high density polyethylene geomembranes (GMBs) of different thicknesses made by the same manufacturer from same GMB resin are investigated. The 1.0, 1.5, 2.0 and 2.4 mm thick GMBs investigated were manufactured during the same production run by changing the pulling speed of the GMB out of the extrusion die, such that, the pulling speed decreased with increasing thickness. There were no differences in the initial HP-OIT or Std-OIT values of the different GMBs. However, there were differences in the key mechanical and physical properties of the GMBs that cannot be simply explained by the increase in the amount of material due to increasing GMB thickness. These differences are explained by differences in the morphological structure of the GMBs arising from the different thermal and stress histories experienced during the manufacturing process. The effects of the differences in the morphological structure are discussed in terms of: the decrease in the relative differences between the stress–elongation curves in the machine and cross-machine directions as thickness increases; changes in the enthalpies of melting and crystallisation by differential scanning calorimetry with changing thickness; and the different stress crack resistance (SCR) for the GMBs. For example, thinner GMBs had a greater difference between the SCR in the machine and cross-machine direction. Increasing the GMB thickness from 1.5 to 2.4 mm resulted in increasing the SCR from ∼ 800 to ∼ 1100 h in the cross-machine direction and decreasing its SCR from ∼ 4100 to ∼ 2000 h in the machine direction. Thus, GMBs of different thickness manufactured from the same resin can be expected to have differences in their physical and mechanical properties that are dependent on the additional material but also the difference in the tension and cooling rate experienced during the manufacturing process.

Creep behaviour of sand–geomembrane interfaces

ABSTRACT: Creep behavior is among the critical properties of soil–geomembrane interfaces. However, there have been very limited studies in this area. In this study, one smooth and one textured high density polyethylene geomembrane were tested for their frictional characteristics with slightly dense Nevada sand. Normal pressures employed in the tests were 25, 50 and 75 kPa. The sustained loadings lasted 240 min, and under each constant normal stress, creep occurred at three levels of shear stress at room temperature. Two loading speeds, 1 and 5 mm/min, were employed in the direct shear tests before and after creep. The study found that the post-creep frictional resistance appeared to be approximately the same as that obtained from a direct shear test without creep. The shear creep behaviour of sand–geomembrane interfaces followed the typical pattern of material creep, and under relatively small normal pressures that did not result in considerable damage of geomembrane surfaces, textured geomembrane interface with sand might exhibit larger shear creep displacement than smooth ones.

Brittle rupture of an aged HPDE geomembrane at local gravel indentations under simulated field conditions

ABSTRACT: The susceptibility of a 1.5 mm thick high-density polyethylene geomembrane to brittle rupture from long-term stress cracking in a simulated municipal solid waste landfill liner is examined. The geomembrane was pre-aged in a leachate at 85°C to lower the notched constant tensile load stress crack resistance of the geomembrane to about 75 h. The aged geomembrane was then used as part of a composite liner system in geosynthetic liner longevity simulators (GLLSs) with a geosynthetic clay liner and sand foundation layer below the geomembrane and a 560 g/m2 geotextile protection layer and 50 mm drainage gravel above the geomembrane. The GLLSs allow the simulation of field conditions including elevated temperatures, overburden pressure, leachate circulation, and composite liner exposure conditions. The geomembrane experienced brittle rupture on the side slopes of the local gravel indentations for temperatures between 55 and 85°C. The higher the liner temperature, the shorter the time to rupture and the higher the tensile strain at rupture. Arrhenius modelling of the test data gave an activation energy of Ea = 112 kJ/mol.

Aging of High-Density Polyethylene Geomembranes of Three Different Thicknesses

AbstractThe effect of geomembrane thickness (1.5, 2.0, and 2.5 mm) on aging when immersed in a synthetic leachate is investigated over a period of approximately 7 years. Based on data at five different temperatures (55, 65, 70, 75, and 85°C), the predicted time required for a reduction in stress crack resistance to 150 h (half the typically specified value) at 35°C is 62% longer for the 2.5 mm than for the 1.5-mm geomembrane tested and 12% longer for the 2.0-mm than for the 1.5-mm geomembrane. Thus, other things being equal, the results suggest a longer time to nominal failure with increasing geomembrane thickness. It is also shown that the data from a proposed stage-parallel testing procedure collected over 2.5 years fit well with data from traditional incubation of virgin samples over almost 7 years and hence provides a viable means of obtaining good data in a reasonable period of time.

Analytical Solution for One-Dimensional Diffusion of Organic Pollutants in a Geomembrane–Bentonite Composite Barrier and Parametric Analyses

AbstractGeomembrane–bentonite composite barrier is known as one of the most reliable and effective technologies for containing underground contamination. Analytical solution for one-dimensional diffusion of an organic solute in the three-layered composite barrier is presented for the case in which the barrier is keyed in aquitard. Parametric analyses were conducted to investigate the effects of partition coefficient and installation location of high-density polyethylene (HDPE) geomembrane, retardation factor, and thickness of bentonite slurry wall on the barrier performance using this analytical solution. The analysis results demonstrate that the containment performance of the composite barrier depends much on the partition coefficient of HDPE geomembrane over the target pollutant. The HDPE geomembrane exhibits an excellent resistance to the hydrophilic organics, which have a low partition coefficient. However, the hydrophobic organics, which have a high partition coefficient, can diffuse readily through ...