Short-term tensile strains that arise from local gravel indentations in municipal solid waste landfill base geomembrane liners are investigated with an emphasis on quantifying how strains are obtained and providing methods for limiting long-term local geomembrane strains below allowable levels. This involved the development of new experimental techniques and apparatuses to study geomembrane strains under controlled conditions. An experimental technique to measure the radial and vertical components of displacement from local gravel indentations in a geomembrane is presented. Geomembrane strains were calculated using large strain-displacement theory, thin shell theory, and the arc elongation method. While radial displacements were found to be small relative to vertical displacements, they were shown to provide the dominant contribution to the maximum strain beneath the centre of the gravel indentation. Both the thin shell and arc elongation methods produced incorrect distributions of strain and also provided magnitudes that significantly underestimated the maximum geomembrane strain. Small-scale screening tests were conducted to gain insight into how key factors including the compressibility of the underlying clay layer, particle size of the overlying gravel, and mass of the geotextile protection layer influence local geomembrane strains. Results are provided that can be used to rule out protection layers that are unable to meet a long-term strain limit, and conversely, identify those that may be able to limit strains below a target strain for further larger scale evaluation. Compaction water contents towards the lower range of water content to achieve an acceptably low hydraulic conductivity of field compacted clay liners were found to be more successful in limiting local strains in the geomembrane. Protection from geotextiles with masses up to 2440 g/m2 were unable to limit geomembrane strains below 1.5% with nominal 50 mm gravel at a temperature of 55°C. Tests with nominal 25 mm gravel revealed that a geotextile with a mass of 1500 g/m2 successfully limited the maximum geomembrane strain below 1.5% at an applied stress of 250 kPa while another geotextile (2440 g/m2) met the strain limit up to applied stresses of 500 kPa at a temperature of 55°C. / Thesis (Master, Civil Engineering) -- Queen's University, 2013-09-30 01:44:54.904

The physical response of composite landfill liners, consisting of a high-density polyethylene geomembrane overlying a compacted clay liner, was examined with an emphasis on quantifying the magnitude and possible implications of sustained tensile strains that may develop in the geomembrane from gravel particles either present on top of or underneath the geomembrane. This involved development of new experimental apparatus to study the effects of time, temperature and chemical action on geomembrane strains. A method based on the concept of time-temperature superposition was developed to predict long-term lower temperature geomembrane strains from short-term higher temperature data. It was found that the short-term response is dominated by loading strains while in the long-term, creep is more significant. The predictions from this method suggest that the protection provided by a nonwoven needle-punched geotextile is not sufficient to limit long-term tensile strains, but a geocomposite may be able to limit geomembrane strains below proposed allowable limits, depending on the applied pressure and landfill temperature. Experiments were also conducted with the new apparatus to examine the implications of sustained tensile strains. It was found that sustained tensile strains resulted in brittle rupture of a notched geomembrane, despite stress relaxation for a geomembrane under a single gravel particle and constant vertical force. The time to rupture depended upon the maximum applied force as well as the stress crack resistance of the geomembrane. This represents the first compelling evidence that long-term geomembrane strains from gravel indentations should be limited. However, even when using an excellent protection layer from overlying gravel particles, gravel particles in the underlying compacted clay liner were identified as another possible source of tension in the geomembrane that for very large landfills may exceed tensile strains limits. For such cases, compacting the top most layer of the clay liner at the lower bound of its acceptable water content combined with careful site inspection such that visible gravel particles are removed from the clay surface will minimize the tensile stains that may develop. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2011-03-18 17:18:41.824

Intact geomembranes are barriers to advective aqueous flow and are often a key component in the design of composite bottom liner and cover systems. During installation, the combination of solar heating, a high coefficient of expansion, and the stiffness of high density polyethylene (HDPE) causes the geomembrane to expand and buckle, forming wrinkles (waves). Up to 20 – 30% of the area of the geomembrane may be below hydraulically connected wrinkles, which could substantially increase leakage through the composite liner if there is a hole on or near a wrinkle in the connected network. To quantify wrinkles at the field scale, a technique for low altitude aerial photography and photogrammetric correction was developed. Wrinkles were quantified for nine field cases involving a variety of installation (area, geomembrane thickness and texture, orientation, subgrade) and weather conditions. The technique was used to quantify the geometry of individual wrinkles (length, width and area) and, more importantly, the length of the longest hydraulically connected wrinkle at each time. Hand measurements of height and width were conducted at five of the cases. Air temperature, solar radiation, and geomembrane surface temperature was recorded as permitted by site conditions and instrumentation. The longest measured connected wrinkle was 5330 m on a 0.61 ha slope. For a 1.5-mm-thick geomembrane, the average wrinkle width over a GCL was 0.20-0.23 m and 0.24 – 0.32 m over a CCL. The average hand-measured wrinkle height was 0.06 m, and the tallest wrinkle measured was 0.18 m. The longest connected wrinkle length was <200 m when the sum of the wrinkle lengths was < 580 m (<8% of the area of the geomembrane was wrinkles). The reported connected wrinkle lengths are significantly longer than previously reported values. When used as input into an existing theoretical leakage solution, these very long wrinkles can explain previous large field measurements of leakage. The results also suggest that simply limiting the time of day when cover soil is placed and/or reducing the area in which wrinkles can form may greatly reduce the length of connected wrinkles after covering. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2012-06-29 16:05:18.598

Geotextile and geomembrane sheets are typically used as a composite system rather than as a stand-alone solution because of their complementary properties of permeability and stiffness. Previous researchers have focused on the large-scale interaction of fiber-texture interfaces while the micromechanical behavior of the internal geotextile structure has received limited attention. Characterizing the variation in the arrangement and distribution of filaments/voids is essential to understanding the micro-scale mechanisms of nonwoven fabrics interacting with counterface materials. This presentation summarizes the results from a study that examined the micromechanical mechanisms involved at needle-punched nonwoven geotextile-textured HDPE geomembrane interfaces and relates the results to the observed macro-scale response. A large displacement direct interface shear device was developed and used in this study to reduce the system errors that often occur with conventional shear devices and to allow internal geotextile strains to occur during shear. Complimentary numerical modeling was undertaken to study interface response. An advanced image analysis technique was applied to allow the evolution of the filament microstructure under various boundary and load conditions to be quantified. The different phases within the geosynthetic interface zone were detected from images captured using high-resolution optical microscopy. The changes of geotextile inner structures were statistically quantified in terms of inter-filament distance changes as well as the local void ratio and inscribing void size distributions. The tensile response of single filaments was measured using a helium neon deflectometer and these measurements were used to evaluate the shear induced filament strain. The study provides insight into the combined role of geomembrane surface topography and geotextile filament structure on macro-scale geosynthetic interface response.

The ageing of high density polyethylene geomembrane (GM) liners used to minimize advection and diffusion of contaminants in municipal solid waste landfill leachate and in hydrocarbon spills to the environment is examined. The evaluation of the ageing of GMs used in landfills involved four components. First, a laboratory-accelerated ageing investigation of a GM exposed to air, water and leachate at elevated temperatures. Service life of a GM (Stage I: Antioxidant depletion, Stage II: Induction, and Stage III: Polymer degradation) is examined. The results demonstrate the critical role of antioxidants in protecting against oxidative degradation. The service life of the GM is predicted. Second, a study was conducted to provide an estimate of Stage I for a GM in a composite liner. The results indicated that immersion tests are too severe and the service life is substantially greater for a GM in composite liner than implied by leachate immersion tests. Third, a comparison of ageing with three different “protection” layers between the GM and overlying gravel and leachate is reported. A slower antioxidant depletion rate is observed when geotextile-geosynthetic clay liner and geotextile-sand-geotextile are applied than with a typical geotextile alone. This could be partially attributed to the attenuation of leachate constituents by the protection layer as well as the buildup of antioxidant concentration on either side of GM thereby reducing the concentration gradient and outward diffusive flux of antioxidants. Fourth, diffusion modelling is used to evaluate the results from immersion and composite liner simulation tests. Diffusion modelling provided a means for predicting the performance of the GMs in conditions other than the typical test conditions. The evaluation of the ageing of GM used in barrier system for hydrocarbon involved two components. First, untreated and fluorinated GMs immersed in jet fuel were tested. Results show that antioxidants depleted at slower rate from fluorinated GM than untreated GM. This suggested a significant beneficial effect of fluorination. Antioxidant depletion time is predicted at field temperatures. Second, the time dependant change in GM samples used at jet fuel containment site constructed in 2001 is reported. The GM is shown to be performing very well. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2009-01-14 10:46:31.089

The physical response of composite landfill liners consisting of a geomembrane on top of a geosynthetic clay liner (GCL) are examined under simulated landfill conditions. The deformation and strains of a 1.5-mm-thick high-density polyethylene geomembrane and thickness and hydraulic performance of a nominally 7-mm-thick GCL are quantified when the composite liner was buried beneath 50 mm coarse gravel, at applied pressures up to 1000 kPa, with a firm sand foundation layer, and with and without a wrinkle in the geomembrane. At an applied pressure of 250 kPa, with either no protection or conventional thick nonwoven needle-punched geotextile protection layers, the tensile strains in the geomembrane exceeded a 3% allowable limit and the GCL was reduced in thickness to as little as 2.2 mm from extrusion of bentonite beneath a gravel particle. Whereas a 150-mm-thick sand protection layer limited strains in the geomembrane to 0.1% and prevented extrusion in the GCL so that deformation was from bentonite consolidation and not from extrusion. A GCL with a thickness of less than 3 mm from extrusion was shown to be susceptible to failure from internal erosion of bentonite in the GCL at hydraulic head differences across the GCL between 1-10 m. Conversely with the sand protection layer, the GCL could withstand a head difference of greater than 100 m without any evidence of internal erosion. Further, the permittivity of an extruded 3.5-mm-thick GCL was found to be 4.5 times larger than a 7-mm-thick GCL that did not experience extrusion. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2008-09-05 10:47:21.783

Gaseous ammonia emissions from livestock production are a well known source of anthropogenic ammonia emissions and have been the subject of numerous studies in Western Europe and in the United States of America. They are deemed responsible for the acidification of ecosystems. Furthermore, ammonia emissions from intensive livestock operations located in the vicinity of major cities induce favourable conditions for smog formation. Ammonia volatilization from manure also reduces its effectiveness as a fertilizer by reducing its nitrogen content, an important nutrient for plant growth. Certain technologies and structures exist to cover manure storage tanks in order to limit these ammonia losses to the atmosphere. Very few studies have been done in Canada where climate and manure management practices differ widely from those in Western Europe and in the United States of America. In this project, a measurement campaign was financed by Agriculture and Agrifood Canada on four commercial livestock production infrastructure to begin the development of national ammonia inventory. Commercial dairy and swine manure storages covered by floating geomembranes were monitored for periods exceeding six months in the Eastern Townships of Quebec. The swine manure storage emitted negligible amounts of ammonia, from 5.9 ?10[superscript -3] to 0.14 [micro]g? m[superscript -2] . s[superscript -1] over the summer time. The dairy manure storage emitted more substantial amounts of ammonia when the manure surface was frozen in winter, from 1.9 to 16 [micro]g. m[superscript -2] ? s[superscript -1], then when unfrozen, 93 to 166 [micro]g? m[superscript -2] ? s[supercript -1]. A structural difference in the covering technology at the dairy manure storage rendered it less airtight than the swine manure storage. Therefore, the efficiency of a cover to limit ammonia emissions from manure is function of its air tightness. Ammonia emission rates from two tie-stall commercial dairy buildings were also monitored in the Eastern Townships of Quebec. Ammonia emission measurements done at building A during winter 2007 ranged from 3.77 to 6.80 g ? day[superscript -1] ? animal[superscript -1] while those performed at building B during summer 2007 were higher and ranged from 11.33 to 18.20 g ? day[superscript -1] ? animal[superscript -1]. These values fall within the wide range of those published for Western Europe and the United States of America. However, unlike studies completed in Europe using similar procedures, the methods used to measure gaseous ammonia concentrations and building ventilation flow rates in this study were validated in controlled environments.

Sliding failures of landfill cover systems are common, and the slip surface is often at the interface between a geosynthetic drainage layer and an underlying textured geomembrane. In an effort to understand the sliding failures, the objectives of this research project are to summarize current regulation and practice in landfill cover design, use experimental methods to characterize the behavior of geosynthetic landfill materials in cover systems approaching failure, and develop models to evaluate the hydraulic performance and stability of landfill cover systems. Inclined plane tests were conducted to explore the behavior of a geosynthetic drainage material/textured geomembrane interface. The interface had effective normal stress dependent strain softening behavior, with more strain softening measured at higher effective normal stresses. A numerical model for confined flow in a drainage layer with a constrained outlet was developed. The model was used to evaluate how water fills and empties from a geosynthetic drainage layer for a variety of inflow conditions and constraints to flow at the outlet. The model was used to demonstrate that a drainage layer that effectively conveys water out of a cover system with a free flowing drainage outlet quickly fills with water when the outlet has a modest constraint to flow. An iterative, numerical model was developed to calculate stability solutions for landfill cover slopes that satisfy force equilibrium and strain compatibility while accounting for effective normal stress dependent strain softening and various pore water pressure conditions. Stability solutions reveal that depending on the water pressure in the drainage layer, the geosynthetic drainage material may experience tension at many points along the slope. It is crucial for the stability of the landfill cover system to maintain free-flowing conditions at the drainage layer outlet. A modest constraint to flow at the outlet has a significant adverse effect on the ability of the landfill cover drainage layer to convey water out of the system, which can lead to instability. The drainage layer outlet should be designed to ensure free flow of water out of the drainage layer. / text

abstract: A series of experiments were conducted to support validation of a numerical model for the performance of geomembrane liners subject to waste settlement and seismic loading. These experiments included large scale centrifuge model testing of a geomembrane-lined landfill, small scale laboratory testing to get the relevant properties of the materials used in the large scale centrifuge model, and tensile tests on seamed geomembrane coupons. The landfill model in the large scale centrifuge test was built with a cemented sand base, a thin film NafionTM geomembrane liner, and a mixture of sand and peat for model waste. The centrifuge model was spun up to 60 g, allowed to settle, and then subjected to seismic loading at three different peak ground accelerations (PGA). Strain on the liner and settlement of the waste during model spin-up and subsequent seismic loading and accelerations throughout the model due to seismic loading were acquired from sensors within the model. Laboratory testing conducted to evaluate the properties of the materials used in the model included triaxial compression tests on the cemented sand base, wide-width tensile testing of the thin film geomembrane, interface shear testing between the thin film geomembrane and the waste material, and one dimensional compression and cyclic direct simple shear testing of the sand-peat mixture used to simulate the waste. The tensile tests on seamed high-density polyethylene (HDPE) coupons were conducted to evaluate strain concentration associated with seams oriented perpendicular to an applied tensile load. Digital image correlation (DIC) was employed to evaluate the strain field, and hence seam strain concentrations, in these tensile tests. One-dimensional compression tests were also conducted on composite sand and HDPE samples to evaluate the compressive modulus of HDPE. The large scale centrifuge model and small scale laboratory tests provide the necessary data for numerical model validation. The tensile tests on seamed HDPE specimens show that maximum tensile strain due to strain concentrations at a seam is greater than previously suggested, a finding with profound implications for landfill liner design and construction quality control/quality assurance (QC/QA) practices. The results of the one-dimensional compression tests on composite sand-HDPE specimens were inconclusive. / Dissertation/Thesis / Doctoral Dissertation Civil and Environmental Engineering 2016

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