Geomembranes (GMB) are normally used as part of the liner system in heap leach pads. There is a need to quantify tensile strains in the geomembrane that could affect short-term puncture and long-term performance of the GMB. In this thesis, short-term tensile strains arising from indentations caused from the material placed both below and above the geomembrane are quantified, and the potential for puncturing is investigated. Experiments were conducted on 1.5 mm high-density (HDPE) and liner low density polyethylene (LLDPE) geomembranes for applied pressures up to 3000 kPa. The geomembrane punctured from underliner material having gravel and sand placed directly beneath the geomembrane and a peak tensile strain of 40% was induced. Increasing the sand fraction to obtain a well graded gravel and sand underliner resulted in peak tensile strains of 14% in the geomembrane and caused no puncture. When geomembrane is underlain by geosynthetic clay liner (GCL) and compacted clay liner, the tensile strains increased with increasing deformability (due to higher water content) of the underlying material. Experiments were also conducted to examine the implications of overliner material and pressure on geomembrane strains. It was found that the overliner having gravel and some sand resulted in 18% tensile strain in the geomembrane at 2000 kPa and 27% for 3000 kPa. A gravelly sand overliner with some silt induced tensile strains of 9% and 12% at 2000 kPa and 3000 kPa respectively. None of the overliners was able to limit stains in the geomembrane to less the maximum recommended geomembrane strain proposed in the literature. A 150-mm-thick silty sand layer placed above coarsest overliner examined reduced the geomembrane strains to 2%, even when subjected to pressures of 3000 kPa. / Thesis (Master, Civil Engineering) -- Queen's University, 2013-02-01 10:33:47.733

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Made available in DSpace on 2014-06-11T19:29:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-07-10Bitstream added on 2014-06-13T18:58:46Z : No. of bitstreams: 1 marcal_r_me_ilha.pdf: 2410808 bytes, checksum: 327612cda811ef63370f475cabbfcc4a (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / As geomembranas são materiais poliméricos que possuem reduzida condutividade hidráulica e sua função principal é a de impermeabilizar e desviar o fluxo de líquidos ou gases. A eficiência das geomembranas como barreiras para controle e desvio de fluxo está diretamente relacionada com a integridade da sua superfície. Dessa maneira, suas propriedades de permeação são extremamente importantes não somente em aterros, mas em obras hidráulicas, de contenção ou que necessitem garantir a estanqueidade. O estudo e a compreensão desses parâmetros possibilitam aos projetistas a compreensão dos fenômenos de infiltração, fugas, vazamentos e transporte difusivo que por ventura possam ocorrer em campo. Dessa forma, esse trabalho apresenta um estudo sobre os parâmetros de permeação e difusão de geomembranas em laboratório para análise e entendimento dessas propriedades em materiais intactos, expostos à radiação ultravioleta e aos efeitos da temperatura em estufa e que apresentem defeitos como micro furos (furos com dimensão menor que a espessura da geomembrana) e furos que possam facilitar o aumento do fluxo, além da avaliação da permeabilidade e processo difusivo aos hidrocarbonetos. Foram realizados diversos ensaios empregando-se um procedimento muito utilizado em geomembranas para determinação da permeabilidade em laboratório, que é a Razão de Transmissão de Vapor d’Água. Diante dos resultados, nota-se, por exemplo, que dentre os processos de degradação, a influência dos danos nas geomembranas é mais significativa do que o próprio efeito da exposição à intempérie provocada no decorrer do tempo, haja vista que um furo de 3,0 mm foi mais significativo no aumento do valor da permeabilidade do que o envelhecimento aos raios UV por 12 anos. O método utilizado na avaliação do processo difusivo... / Geomembranes are polymeric materials that have low hydraulic conductivity and its main function is to insulate and divert the flow of liquids or gases. The efficiency of geomembranes as barriers to control and diversion of flow is directly related to the integrity of its surface. Thus, their permeation properties are extremely important not only in landfills, but in hydraulic works, containment, or who need to ensure tightness. The study and understanding of these parameters allow designers to understand the effects of infiltration, leaks, spills, and diffusive transport that might occur by chance in the field. Thus, this paper presents a study on the parameters of permeation and diffusion of geomembranes in the laboratory for analysis and understanding of these properties in intact materials exposed to ultraviolet radiation and effects of temperature in the greenhouse and they have defects such as micro holes (holes dimension less than the thickness of the geomembrane) and holes which can facilitate flow increases, besides the evaluation of permeability and diffusion process for hydrocarbons. Several trials were conducted employing a procedure commonly used in geomembranes to determine the permeability in the laboratory, which is the ratio of Water Vapor Transmission. The results showed, for instance, that among the degradation processes, the influence of damage on geomembranes is more significant than the actual effect of exposure to atmospheric conditions caused over time, given that a hole of 3.0 mm was more significant increase in the permeability value than the UV aging for 12 years. The method used to evaluate the... (Complete abstract click electronic access below)

Orientador: Paulo César Lodi / Banca: Edson Pereira Tangerino / Banca: Fagundes Júnio René Toledo / Resumo: As geomembranas são materiais poliméricos que possuem reduzida condutividade hidráulica e sua função principal é a de impermeabilizar e desviar o fluxo de líquidos ou gases. A eficiência das geomembranas como barreiras para controle e desvio de fluxo está diretamente relacionada com a integridade da sua superfície. Dessa maneira, suas propriedades de permeação são extremamente importantes não somente em aterros, mas em obras hidráulicas, de contenção ou que necessitem garantir a estanqueidade. O estudo e a compreensão desses parâmetros possibilitam aos projetistas a compreensão dos fenômenos de infiltração, fugas, vazamentos e transporte difusivo que por ventura possam ocorrer em campo. Dessa forma, esse trabalho apresenta um estudo sobre os parâmetros de permeação e difusão de geomembranas em laboratório para análise e entendimento dessas propriedades em materiais intactos, expostos à radiação ultravioleta e aos efeitos da temperatura em estufa e que apresentem defeitos como micro furos (furos com dimensão menor que a espessura da geomembrana) e furos que possam facilitar o aumento do fluxo, além da avaliação da permeabilidade e processo difusivo aos hidrocarbonetos. Foram realizados diversos ensaios empregando-se um procedimento muito utilizado em geomembranas para determinação da permeabilidade em laboratório, que é a Razão de Transmissão de Vapor d'Água. Diante dos resultados, nota-se, por exemplo, que dentre os processos de degradação, a influência dos danos nas geomembranas é mais significativa do que o próprio efeito da exposição à intempérie provocada no decorrer do tempo, haja vista que um furo de 3,0 mm foi mais significativo no aumento do valor da permeabilidade do que o envelhecimento aos raios UV por 12 anos. O método utilizado na avaliação do processo difusivo... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Geomembranes are polymeric materials that have low hydraulic conductivity and its main function is to insulate and divert the flow of liquids or gases. The efficiency of geomembranes as barriers to control and diversion of flow is directly related to the integrity of its surface. Thus, their permeation properties are extremely important not only in landfills, but in hydraulic works, containment, or who need to ensure tightness. The study and understanding of these parameters allow designers to understand the effects of infiltration, leaks, spills, and diffusive transport that might occur by chance in the field. Thus, this paper presents a study on the parameters of permeation and diffusion of geomembranes in the laboratory for analysis and understanding of these properties in intact materials exposed to ultraviolet radiation and effects of temperature in the greenhouse and they have defects such as micro holes (holes dimension less than the thickness of the geomembrane) and holes which can facilitate flow increases, besides the evaluation of permeability and diffusion process for hydrocarbons. Several trials were conducted employing a procedure commonly used in geomembranes to determine the permeability in the laboratory, which is the ratio of Water Vapor Transmission. The results showed, for instance, that among the degradation processes, the influence of damage on geomembranes is more significant than the actual effect of exposure to atmospheric conditions caused over time, given that a hole of 3.0 mm was more significant increase in the permeability value than the UV aging for 12 years. The method used to evaluate the... (Complete abstract click electronic access below) / Mestre

In compacted Na-montmorillonite membranes, the pore-size, and surface charge will influence filtration processes of solutes. A dead-end hyperfiltration setup was utilized to: (a) study the intrinsic retention, membrane filtration coefficient, and solution flux of different membrane configurations and (b) model nitrate break-through effluent concentrations through the membrane. Scanning electron microscopy and solute analytical techniques were employed to assess what critical components of micro-pore parametrics would prevail in a non-bio stimulated remediation of simulated agricultural wastewater. Although high content bentonite membrane configurations (5 g clay at 2500 psi) offered better solute rejections with a 30 percent increase in the cell concentration, the compaction of the membrane had the most deterministic influence on the solution flux. The results reveal hyperfiltration of nitrate ions is a function of the compaction pressure and composition of bentonite in the mixed soils. High content bentonite membranes compacted at the optimal pressures offer promising solutions to nitrate contaminant remediation.

Dams are among the most critical of civil engineering structures and are susceptible to damage due to seepage. Geomembranes have been used to minimize seepage problems in dams since 1959. However, geomembranes are vulnerable to damage, in the form of tears and punctures, during installation and throughout the service life. These defects impact the effectiveness of a geomembrane as an infiltration barrier resulting in leakage through the geomembrane liner and into the body of the dam. The majority of previous studies conducted to investigate leakage through defects in geomembranes considered heads below 0.3 m, which corresponds to flow for conditions experienced by landfill liners. The main objectives of this study were to quantify the leakage rate through defects in geomembrane lining systems for dam and to evaluate the implications of the leakage on the performance of dams. Experimental, analytical and numerical studies were conducted as part of this investigation. The experimental testing program included permeameter cell tests for the following lining systems: i) geomembranes over clay layers, ii) geomembranes over sand layers and iii) geomembranes over geosynthetic clay liners. The permeameter tests were conducted to investigate the effects of soil type, initial water content, dry unit weight and hydraulic head on leakage through a defect in a geomembrane liner. The analytical component was conducted to evaluate the transmissivity at the interface and radius of wetted area for the tests conducted as part of the experimental component. The numerical component of this study was performed using the finite element method to simulate the experimental tests and the performance of actual dams. Ultimately, the laboratory tests and subsequent analyses were used to develop a set of tools (e.g., empirical models, design recommendations) that are expected to assist engineers in the design of geomembrane lining systems for dams. Also, the study was used to identify and address potential concerns (e.g., global stability) that may result in failure of systems in which geomembrane liners are used. This study is expected to contribute to a better understanding of the performance of geomembranes as dam liners. The presence of a geomembrane, even with a defect, was found to reduce the amount of leakage that occurs through a soil layer. New predictive equations were developed to estimate leakage through defects in composite lining systems. The finite element analyses indicated that a dam with a geomembrane with very large defects would not develop pore pressures that were similar to those observed for an unlined dam. The factor of safety for the unlined dam was improved by the placement of a geomembrane on the upstream face. Consequently, a geomembrane may also eliminate the need for a blanket drain at the downstream toe, which could decrease the cost of construction. / text

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During the past decades there has been an increase in the use of geosynthetics in construction due to their versatility in providing a wide array of functions such as reinforcement, containment, separation, filtration and drainage. Often, geosynthetics are used in conjunction with other geosynthetics to accomplish these functions. However, geosynthetics create possible planes of weakness which can lead to failures. Textured geomembranes are widely used within landfill and mining industries due to their containment and shear strength properties, however, there are subjected to a wide array of loads and environments which are potentially hazardous, as such is of utmost importance to retain their integrity in order to avoid ecological disasters. The challenge is to understand how geomembranes resist damage, wear and which of these factors control the development of wear on textured geomembranes. Digital imaging techniques have been used in order to develop a protocol that describes the quantification of wear on textured structured geomembranes. Direct shear tests were performed to induce wear on the geomembrane textures (asperities) to analyse the wear mechanisms and study the factors that induce wear on the asperities. The research showed that normal stress and shear displacement have a major role in the development of wear on interfaces. However, the geometrical characteristics of the geomembrane asperities control the amount of wear the geomembrane can sustain without significant shear strength loss. These outcomes help to better understand the behaviour of interfaces which have as component geomembranes, leading to more robust designs. This study also proposed new asperity texture shapes by using Rapid Prototyping (RP) techniques, such as Selective Laser Sintering and Fused Filament Fabrication. Using RP techniques to create new textures for the geomembrane, could allow the creation of textures which have increased shear strength thresholds and better withstand wear, allowing for more advanced and economical designs.

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