Geomembrane Thickness Research Articles

Geomembrane leaks detection and leakage correlation factor analysis of composite liner systems for fifty-five (55) solid waste landfills in China

In composite liner system (CLS), there are little field data on the number, size, and shape of geomembrane (GMB) holes, which are the key parameters to identify and evaluate the volume of leachate leakage from landfills. In this paper, in-situ detection of GMB holes in composite liner systems of 55 solid waste landfills in China was conducted by electrical leak location (ELL) method, and the following conclusions were drawn. The holes frequency, equivalent radius, and theoretical leakage volume of double-layer systems are lower than those of single-layer systems under the same geotextile (GT) density by 28.2%, 51.4%, and more than 60%, respectively. As the thickness of GMB increases, the holes frequency, equivalent radius and theoretical leakage volume reduce observably. Regarding protecting GMB, the density of geotextiles should not be less than 600 g/m2. Through the analysis of various correlation factors, the thickness of geomembrane is an important parameter affecting the amount of leakage. This study will provide a reference for analyzing the data of field investigation, which would provide constructive suggestions for the composite liner system.

Performance analysis of geomembrane subjected under elevated temperatures

A macro-level analysis has been carried out using Linear Regression Analysis in MS Excel to determine the half-life of Geomembrane (GM) when it is being exposed to higher temperatures. Four different GM were taken for the study and it is observed that the SCR of GM is high at 105 °C, 115 °C when compared to 95 °C, this may be due to annealing effect as it increases the thickness of GM thereby SCR of GM has increased. Half-life observed for GM 1 is 2.5, 1, 0.68 years at 95 °C, 105 °C, 115 °C respectively, for GM 2 is 1.8, 1, 0.5 years at 95 °C, 105 °C, 115 °C, for GM 3 is1.7, 1, 0.5 years at 95 °C, 105 °C, 115 °C & for GM 4 is 1.8, 0.5 years at 105 °C, 115 °C. It is observed that GM subjected to higher temperature has a greater effect on it. Exposure of GM to elevated temperature closure to its melting point has reduced its durability significantly.

Antioxidant depletion patterns of high-density polyethylene geomembranes in landfills under different exposure conditions

The service life of high-density polyethylene (HDPE) geomembranes is directly determined by the landfill environment, and the antioxidant depletion stage is the first and most important stage of the HDPE geomembrane aging process. In this study, the antioxidant depletion stage was chosen to investigate the effects of different exposure environments on the HDPE geomembrane lifespan. The antioxidant depletion rate (ADR) and the antioxidant depletion time (ADT) of HDPE geomembranes under various exposure conditions were calculated based on the aging parameters obtained by fitting the collected reported data with the Arrhenius model. Also, the influence of exposure conditions on the HDPE geomembrane performance degradation was analyzed. The results showed that the aging method had the greatest effect on the antioxidant depletion period, while the HDPE geomembrane thickness had the least effect. The ADR sensitivity to brand/material, aging method, leachate components, and exposure medium decreased with increasing temperature; only the sensitivity to thickness showed a slight increasing tendency with increasing temperature. The ADTs of HDPE geomembranes under different exposure conditions ranged from 6 years to 900 years, indicating that the HDPE geomembranes can complete the service time of landfills under reasonable exposure conditions. This study provides a reliable methodological basis for the risk control and life prediction of HDPE geomembranes.

Experimental Study on Shear Strength of Geomembrane Welding Seams under Different Inflation Time and Pressure

The shear strength of geomembrane welding seams (GWSs) is one of the key factors for the reliability of geotechnical anti-seepage system. In order to study the evolution law of shear strength of GWSs under different inflation time and pressure, the weld shear strength tests of seven different thicknesses of HDPE geomembrane were carried out under different inflation time and pressure conditions. The test results show that the weld shear strength increases with the increasing geomembrane thickness under the same inflation time (3min or 10min) or the same test inflation pressure (0.1MPa or 0.2MPa). Additionally, the trend of all test curves is similar. The hot-welding method shows good stability in weld shear strength of different thicknesses of HDPE geomembrane. The shear strength values of GWSs of the same thickness under different inflation pressures and inflation times are similar. During the shearing process of the welds, the weakened area of the material at the joint between the edge of the weld and the geomembrane base material is most likely to be destroyed. The corresponding test results can provide reference for GWS inspection and related engineering.

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.

Effects of Geomembrance on the Contaminant Transport in Compacted Clay Liner System

An analytical model is established to predict the seepage performance of the liner system composed of a compacted clay liner (CCL) covered by a geomembrane (GM). The contaminant of Pb2+diffusing through the geomembrane is assumed to be a steady-state process. The liner systems with low leakage performance are usually utilized in the municipal solid waste landfills to prevent the contaminants of the leachate from polluting the groundwater and soil beneath the landfill. To investigate the seepage rate of the Pb2+in the liner systems of the landfill considering the effects of the geomembrance, the influence of the geomembrance on the seepage performance of the liner system is studied. Parametric analyses are conducted to study the effects of the thickness of GM and the number of defects in the GM on the leakage performance of the liner system. In conclusion, some suggestions for the design of the municipal solid waste landfills are proposed based on the analyses results.

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.

Ageing of HDPE geomembranes in jet fuel A-1

ABSTRACT: The latest findings regarding the ageing of high-density polyethylene (HDPE) geomembrane (GM) exposed to jet fuel are presented. Data from std-OIT and HP-OIT tests both indicate that some component(s) of the antioxidant package are readily leached into the jet fuel but once this component is removed the OIT values remain relatively stable for up to at least 4 years. The std-OIT depletion rates for the readily leachable component of the antioxidant package are estimated from the available data. Based on the jet fuel immersion test at 23°C the depletion time to reach the residual standard oxidative induction time (OIT) is 1.6 years for 1.5 mm thick conventional GM and 5.5 years for the 1.5 mm fluorinated GM. Thus fluorination had a significantly beneficial effect in terms of slowing antioxidant depletion. Arrhenius modelling based on data at three temperatures (23, 9 and −22°C) is used to predict std-OIT depletion times at a temperature (−1°C) applicable to containment of jet fuel spill at Brevoort Island in the Arctic. The estimated depletion time ranged from 14–24 years for 1.5 mm thick untreated GM, 22–33 years for 2 mm untreated GM, and 26–33 years for 1.5 mm fluorinated GM. For GMs with a similar composition, the OIT depletion rate decreased approximately with the square of GM thickness. At 23°C the depletion rate in the diffusion test was only about one-quarter of that in an immersion test. Tensile elongation at yield increased with time of immersion in jet fuel. Tensile yield properties and initial tear resistance of the GM were lower when the GM was wet with jet fuel than when dry. However, no significant change in dry initial tear resistance was observed. No significant change in crystallinity was observed in GM exposed to jet fuel. The immersion data suggest that the 1.5 mm f-HDPE GM liner used to containing the hydrocarbon spill on Brevoort Island is likely to perform well for a period well in excess of 25 years at the average field temperature (−1°C). Based on the findings from the diffusion tests with jet fuel on one side and water on the other (i.e. similar exposure conditions to that in the field), the time to antioxidant depletion is likely to about four times longer than when immersed in jet fuel and so the depletion time in the field under these conditions is projected to be in excess of 100 years. These tests will need to be run for a much longer period of time to allow a better estimate to be made of the depletion rate of remaining antioxidants and service life of GM exposed to jet fuel.

Effects of Thickness on the Aging of HDPE Geomembranes

The results of an accelerated aging test program to evaluate the effect of thickness on the depletion of antioxidants from high-density polyethylene HDPE geomembranes and subsequent degradation of the physical properties are reported. Three commer- cially available HDPE geomembranes having nominal thicknesses of 1.5, 2.0, and 2.5 mm were examined. The geomembranes were immersed in a synthetic leachate at 85, 70, 55, and 22° C and tested for oxidative induction time, crystallinity, melt index MI, tensile properties, and stress-crack resistance. The antioxidant depletion rate for the 1.5 mm geomembrane was faster than for the 2.0 and 2.5 mm geomembranes. Antioxidant depletion time was predicted at representative landfill temperatures of 20- 60° C using Arrhenius modeling and was found to increase with geomembrane thickness for the three geomembranes examined. Based on the results of crystallinity, MI, and stress-crack resistance, the degradation of the geomembrane was slowest for the thickest geomembrane. These results suggest that a thicker geomembrane may have a longer service life other things being equal.

Puncture resistance of PVC geomembranes using the truncated cone test

This paper presents an experimental study to develop a design procedure for the puncture behavior of polyvinyl chloride (PVC) geomembranes. The puncture resistance was measured using the truncated cone test, in which truncated cones are used as puncture points. The heights of the truncated cones are varied to determine the critical cone height, which is the height at which geomembrane puncture occurs for a given pressure. A cushion geotextile is not used in any test to enhance puncture resistance because of the large cone heights required to puncture PVC geomembranes. Critical cone heights are presented for 0.5 mm, 0.75 mm and 1.0 mm thick PVC geomembranes. The results of these tests show that as the thickness of the PVC geomembrane increases, the critical cone height increases. This indicates an increased puncture resistance with increasing geomembrane thickness. The results of the puncture tests on PVC geomembranes are compared with other types of geomembrane, e.g. smooth and textured 1.5 mm thick high-density polyethylene and 1.0 mm thick linear low-density polyethylene. This comparison shows that the puncture resistance of PVC geomembranes used in this investigation exceeds that of polyethylene geomembranes, even though the PVC geomembranes are thinner.

Behavior of waves in high density polyethylene geomembranes: a laboratory study

In this laboratory study, the behavior of waves of the type seen in field deployed high density polyethylene (HDPE) geomembranes was studied. Four experimental variables were evaluated: normal stress, original wave height, thickness of geomembrane and temperature. Twenty-five separate tests were conducted, each for 1000 hours duration. Each of the tests utilized HDPE geomembranes with strain gages attached in a number of critical locations. The results of the 1000-hour strain measurements were modeled and extrapolated to 10,000 hours using the Kelvin-chain model. The measured and extrapolated strains were then converted to stresses via the Maxwell–Weichert model and stress relaxation master curves. With the completion of the experiments and their extrapolation into a near steady state condition, it was found that tensile strains up to 4.9% remained in the geomembranes. The equivalent residual stresses were as high as 22% of the yield stress. Full contacts between the geomembrane and the underlying subgrade soil was not achieved in any of the tests performed.

Transport of Organic Compounds in Thermoplastic Geomembranes. I: Mathematical Model

A quasi-two-dimensional partition-diffusion transport model was developed to determine the diffusion coefficient and partition coefficient for various types of geomembranes from measurements of aqueous organic compound concentrations in a confined, double-compartment apparatus with a geomembrane separating the two compartments. The geomembranes tested were high-density polyethylene (HDPE), very low-density polyethylene (VLDPE), and polyvinyl chloride (PVC) and the permeants were mixtures of methylene chloride, toluene, trichloroethylene (TCE), and \im-xylene at 10–100 mg/L. The diffusion coefficient increased exponentially with aqueous concentration and decreased exponentially with geomembrane thickness. The partition coefficient was unaffected by compound concentration and membrane thickness. As HDPE geomembranes were stretched by 5% of their original length, the partition coefficient increased by 0.15–0.6 times. VLDPE had 1.8–3.3 times greater partition coefficients and 1.6–2.8 times greater diffusion coefficients than HDPE, while PVC had 6.2–8.3 times greater partition coefficients and 1–1.8 times greater diffusion coefficients than HDPE.

Application of Geotextile/Geomembrane Composite Liner for Infiltration Prevention in Xiaolingtou Rock-Fill Dam

The rock-fill dam at the Xiaolingtou Reservoir is 36.4 m high and uses a geotextile/geomembrane composite liner to prevent seepage. The composite consists of geotextiles bonded to both sides of a geomembrane. The seepage prevention properties of the composite are theoretically analysed, and equations to calculate the design strength and geomembrane thickness have been introduced. The transition material on the side slopes of the dam directly effects the selection of a design strength for the composite. The laboratory testing program carried out to optimize the cushion material gradation of for the Xiaolingtou rock-fill dam is described. The horizontal displacement, vertical settlement, maximum and minimum principal stresses in the rock-fill dam during construction and water storage periods have been analysed by the finite element method.

Theoretical Analysis of Geomembrane Puncture

A theoretical analysis of the mechanism of geomembrane puncture based on a simple model is presented. The analysis shows that the geomembrane puncture resistance depends on the diameter of the contact area between the geomembrane and the puncturing object, the thickness of the geomembrane, and the tensile characteristics of the geomembrane. An equation is established that makes it possible to express the geomembrane puncture resistance measured in a probe test as a function of the geomembrane characteristics and the diameter of the probe. Predictions made with this equation are found to be consistent with the limited laboratory test data which were reviewed. The analysis is then used to establish a relationship between a geomembrane resistance to puncture measured in a laboratory probe test and the resistance to puncture of a geomembrane subjected to pressure applied by a liquid while resting on a layer of stones of approximately uniform size and shape. A special relationship is presented for the case of rounded stones. The paper also presents relationships between geomembrane resistances to puncture by stones under different sets of conditions characterized by the stone size and shape, and the geomembrane thickness and tensile characteristics. The use of these relationships is illustrated by design examples.

Yield of scratched geomembranes

In this paper, it is demonstrated that geomembranes that have a stress-strain curve with a yield peak, such as high-density polyethylene (HDPE) geomembranes, yield at a tensile strain that is significantly influenced by scratches on the surface of the geomembrane. It is shown that scratched HDPE geomebranes can exhibit yield at strains that are one-third to one-half the yield strain of intact geomembranes. The method presented in this paper makes it possible to quantify the reduction in HDPE geomembrane yield strain due to scratches as a function of the scratch depth and the geomembrane thickness. Alternatively, the method can be used to select the thickness of an HDPE geomembrane for a given required yield strain when a certain scratch depth is expected.

Mass flux of organic chemicals through polyethylene geomembranes

ABSTRACT: Lining of waste storage and disposal sites is a common practice to prevent hazardous waste constituents from migrating out of the facility into the surrounding environment. Recently, geomembranes have been widely used to line the waste storage and disposal sites and are expected to be even more common in the future. However, there are not enough data available on the mass transport of organic chemicals through geomembranes by the physicochemical process of partition and diffusion. In this study, partition and diffusion coefficients were measured using a gravimetric method for high‐density polyethylene (HDPE) geomembrane in acetone, chlorobenzene, ethyl acetate, ethylbenzene, n‐hexane, methylene chloride (MC), n‐octane, toluene, trichloroethylene (TCE), and m‐xylene. Sorption tests were also conducted with mixtures of TCE, MC, toluene, gasoline, and aqueous solutions of TCE, MC, toluene, and m‐xylene. The effect of geomembrane thickness on the mass flux parameters was also evaluated. A mathematical model with a time‐dependent diffusion coefficient successfully simulated sorption curves of pure chemicals. The partition and diffusion coefficients of individual organic compounds in a mixture were accurately predicted from the mass‐transport parameters of individual pure chemicals by multiplying them with their mole fractions. Low‐density polyethylene geomembranes had approximately 4 times and 10 times greater partition and diffusion coefficients than HDPE geomembranes, respectively. A mathematical model together with the experimentally determined parameters was used to predict the mass flux of selected organic chemicals present in gasoline through a 10.2‐cm (4‐in.) HDPE pipe (0.4‐cm [0.16‐in.] thick).