The permeability of plasticized polyvinyl chloride (PVC-P) geomembranes (GMBs) is of significant importance to the safe operation of the impermeable structures and even the project. To avoid the drawbacks of adopting the permeability coefficient to characterize permeability traditionally, this paper presents a mathematical model of porosity and seepage discharge based on the results of the vertical permeability test and porosity obtained from low-field nuclear magnetic resonance (NMR) test, and the applicability of porosity to evaluate the permeability was explored combined with the dynamic distribution of pores and pore radius. The results show that the low-field NMR technology with 1H atoms as the probe can accurately measure the distribution of pores and pore radius in the PVC-P GMB. The proportion of micropores (Mic), mesopores (Mes) and macropores (Mac) and the shrinkage or development of pore radius are primarily responsible for the variation of the porosity. The porosity is closely correlated with the seepage discharge, and the constructed model can accurately predict the seepage discharge. Furthermore, the porosity can provide technical support for the evaluation of the permeability of PVC-P GMBs and the selection of appropriate GMBs for engineering design.
{"title":"Permeability mechanism of PVC-P geomembranes based on low-field NMR technology","authors":"X. L. Zhang, Yuehua Wu, C. J. Yin, X. Y. Gu","doi":"10.1680/jgein.22.00409","DOIUrl":"https://doi.org/10.1680/jgein.22.00409","url":null,"abstract":"The permeability of plasticized polyvinyl chloride (PVC-P) geomembranes (GMBs) is of significant importance to the safe operation of the impermeable structures and even the project. To avoid the drawbacks of adopting the permeability coefficient to characterize permeability traditionally, this paper presents a mathematical model of porosity and seepage discharge based on the results of the vertical permeability test and porosity obtained from low-field nuclear magnetic resonance (NMR) test, and the applicability of porosity to evaluate the permeability was explored combined with the dynamic distribution of pores and pore radius. The results show that the low-field NMR technology with 1H atoms as the probe can accurately measure the distribution of pores and pore radius in the PVC-P GMB. The proportion of micropores (Mic), mesopores (Mes) and macropores (Mac) and the shrinkage or development of pore radius are primarily responsible for the variation of the porosity. The porosity is closely correlated with the seepage discharge, and the constructed model can accurately predict the seepage discharge. Furthermore, the porosity can provide technical support for the evaluation of the permeability of PVC-P GMBs and the selection of appropriate GMBs for engineering design.","PeriodicalId":12616,"journal":{"name":"Geosynthetics International","volume":"20 7","pages":""},"PeriodicalIF":4.5,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41301029","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Geosynthetics can be exposed to varying temperature and moisture conditions when embedded in the soil, which can affect their mechanical properties. However, existing testing standards do not account for extreme environmental conditions, such as low temperatures and ice formation. This study aims to understand the effect of temperature variation and ice formation on the tensile properties of dry and wet geosynthetics by conducting single-rib tensile tests on a wicking geogrid composite in a temperature chamber. Tensile stress-strain curves were reported at various temperatures for dry samples (−40°C to 40°C) and wet samples (0°C to −40°C). The results show that the tensile strength and stiffness of dry and wet samples increase while ultimate strain decreases as temperatures decrease. Freezing of water in wet samples also accelerates the rate of increase in ultimate strength and decrease in ultimate strain. The failure mode of the geogrid composite also changes with temperature, occurring at the middle junction at higher temperatures and closer to the end junctions with a fibrous appearance at lower temperatures. These findings provide insights into the significance of varying environmental conditions on geosynthetic properties.
{"title":"Investigating the effect of temperature and water freezing on the response of geogrid composite","authors":"J. Jarjour, M. Meguid","doi":"10.1680/jgein.23.00078","DOIUrl":"https://doi.org/10.1680/jgein.23.00078","url":null,"abstract":"Geosynthetics can be exposed to varying temperature and moisture conditions when embedded in the soil, which can affect their mechanical properties. However, existing testing standards do not account for extreme environmental conditions, such as low temperatures and ice formation. This study aims to understand the effect of temperature variation and ice formation on the tensile properties of dry and wet geosynthetics by conducting single-rib tensile tests on a wicking geogrid composite in a temperature chamber. Tensile stress-strain curves were reported at various temperatures for dry samples (−40°C to 40°C) and wet samples (0°C to −40°C). The results show that the tensile strength and stiffness of dry and wet samples increase while ultimate strain decreases as temperatures decrease. Freezing of water in wet samples also accelerates the rate of increase in ultimate strength and decrease in ultimate strain. The failure mode of the geogrid composite also changes with temperature, occurring at the middle junction at higher temperatures and closer to the end junctions with a fibrous appearance at lower temperatures. These findings provide insights into the significance of varying environmental conditions on geosynthetic properties.","PeriodicalId":12616,"journal":{"name":"Geosynthetics International","volume":" ","pages":""},"PeriodicalIF":4.5,"publicationDate":"2023-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47612292","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Understanding the failure mechanism of geosynthetic-reinforced embankments on soft foundations is crucial for ensuring safety in design. This study aimed to investigate the failure mechanism and stability of embankments reinforced with varying layers and lengths of geosynthetic reinforcements utilizing centrifuge testing and numerical modeling. The results show that a foundation under construction exhibits a progressive shear failure coupled with a tensile failure of the geosynthetic reinforcement. The plastic shear strain in the soft clay layer initiates at the centerline, shoulder and the embankment toe and propagates both forward and backward until a critical slip surface develops. The tensile failure of the geosynthetic was observed at the embankment center. Comparatively, implementing two shorter layers of geosynthetics proved more advantageous for overall stability than using a single layer with the entire length. By analyzing the strain distribution in the foundation, the deformation modes of the embankment reinforced by different numbers of geosynthetic layers were clarified. It found that increasing the number of geosynthetic layers extended the active shear zone in soft clay.
{"title":"Centrifuge modeling of the progressive failure of geosynthetic-reinforced embankments","authors":"G. Zheng, B. Xia, H. Zhou, X. Yu, Y. Diao, Y. Du","doi":"10.1680/jgein.23.00061","DOIUrl":"https://doi.org/10.1680/jgein.23.00061","url":null,"abstract":"Understanding the failure mechanism of geosynthetic-reinforced embankments on soft foundations is crucial for ensuring safety in design. This study aimed to investigate the failure mechanism and stability of embankments reinforced with varying layers and lengths of geosynthetic reinforcements utilizing centrifuge testing and numerical modeling. The results show that a foundation under construction exhibits a progressive shear failure coupled with a tensile failure of the geosynthetic reinforcement. The plastic shear strain in the soft clay layer initiates at the centerline, shoulder and the embankment toe and propagates both forward and backward until a critical slip surface develops. The tensile failure of the geosynthetic was observed at the embankment center. Comparatively, implementing two shorter layers of geosynthetics proved more advantageous for overall stability than using a single layer with the entire length. By analyzing the strain distribution in the foundation, the deformation modes of the embankment reinforced by different numbers of geosynthetic layers were clarified. It found that increasing the number of geosynthetic layers extended the active shear zone in soft clay.","PeriodicalId":12616,"journal":{"name":"Geosynthetics International","volume":" ","pages":""},"PeriodicalIF":4.5,"publicationDate":"2023-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43684652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, geocell reinforcements are proposed as a thrust countermeasure for shallowly buried pipeline bends and tees. The proposed method is easy to construct and has shorter construction time since it does not require curing compared to conventional concrete blocks. The lateral loading tests were conducted on the plates reproducing pipe bends or tees to verify their effectiveness while understanding deformation mechanisms. In addition to changing the conditions of plate width and geocell pocket size, additional experiments were conducted with different geocell reinforcement dimensions, geocell tensile stiffness and seam tensile properties. An equation for predicting the force-displacement relationship was developed as part of the proposed design method. The experimental results showed that the sides of the reinforced ground are not fully integrated when the width of the geocell reinforcement is large relative to the plate width. It was also found that the maximum force hardly decreased, although the displacement increased slightly due to the reduction of the tensile stiffness of the geocell and the tensile force at the geocell seams. Moreover, a hyperbolic approximation of the displacement-force relationship for geocell reinforcement loaded was proposed, and the calculated values agreed well with the experimental values.
{"title":"Lateral force-displacement relationships for shallowly buried pipe reinforced by geocell","authors":"Y. Sawada, M. Kitada, H. Ling, T. Kawabata","doi":"10.1680/jgein.22.00325","DOIUrl":"https://doi.org/10.1680/jgein.22.00325","url":null,"abstract":"In this study, geocell reinforcements are proposed as a thrust countermeasure for shallowly buried pipeline bends and tees. The proposed method is easy to construct and has shorter construction time since it does not require curing compared to conventional concrete blocks. The lateral loading tests were conducted on the plates reproducing pipe bends or tees to verify their effectiveness while understanding deformation mechanisms. In addition to changing the conditions of plate width and geocell pocket size, additional experiments were conducted with different geocell reinforcement dimensions, geocell tensile stiffness and seam tensile properties. An equation for predicting the force-displacement relationship was developed as part of the proposed design method. The experimental results showed that the sides of the reinforced ground are not fully integrated when the width of the geocell reinforcement is large relative to the plate width. It was also found that the maximum force hardly decreased, although the displacement increased slightly due to the reduction of the tensile stiffness of the geocell and the tensile force at the geocell seams. Moreover, a hyperbolic approximation of the displacement-force relationship for geocell reinforcement loaded was proposed, and the calculated values agreed well with the experimental values.","PeriodicalId":12616,"journal":{"name":"Geosynthetics International","volume":" ","pages":""},"PeriodicalIF":4.5,"publicationDate":"2023-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42060915","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The antioxidant-stabilizer depletion of four 1.5-mm HDPE geomembranes from the same manufacturer each with a different resin and additive package is examined in air and a synthetic municipal solid waste leachate at a range of temperatures (40-95°C) for 7.5 years. Two were formulated for high-temperatures and used polyethylene of raised temperature resistance (PE-RT) resins while two used more conventional HDPE geomembrane formulations. The depletion of protective antioxidants and stabilizers was monitored using standard and high-pressure oxidative induction time (OIT) tests and the notably different depletion times for both OIT tests implied they were detecting different groups of AO-S. Although both PE-RT GMBs showed significantly slower AO-S depletion at 85°C in air compared to the conventional PE GMBs, only one PE-RT GMB maintained this status in 85°C leachate, highlighting the limitation of air aging tests (and importance of fluid immersion tests). The importance of running immersion tests long enough to reveal the residual HP-OIT value is stressed. The roles of stabilizer mobility and solubility in polyethylene and their suspected involvement in residual HP-OIT behavior is also illustrated.
在空气和合成城市固体垃圾渗滤液中，在温度范围(40-95°C)下，研究了来自同一制造商的四种1.5 mm HDPE土工膜的抗氧化剂-稳定剂消耗情况，每种膜具有不同的树脂和添加剂包装。其中两种用于高温和使用耐高温聚乙烯(PE-RT)树脂，而两种使用更传统的HDPE土工膜配方。采用标准氧化诱导时间(OIT)和高压氧化诱导时间(OIT)测试监测保护性抗氧化剂和稳定剂的消耗，两种OIT测试的消耗时间明显不同，表明它们检测的是不同组的AO-S。尽管与传统PE GMB相比，两种PE- rt GMB在85°C空气中表现出明显较慢的AO-S耗损，但只有一种PE- rt GMB在85°C渗滤液中保持这种状态，这突出了空气老化试验的局限性(以及流体浸泡试验的重要性)。强调了进行足够长时间的浸没试验以揭示残余HP-OIT值的重要性。稳定剂在聚乙烯中的迁移性和溶解度的作用以及它们在残余HP-OIT行为中的疑似参与也被说明。
{"title":"Antioxidant-stabilizer depletion of 4 HDPE geomembranes with high HP-OIT in MSW leachate","authors":"M. Clinton, R. Rowe","doi":"10.1680/jgein.23.00041","DOIUrl":"https://doi.org/10.1680/jgein.23.00041","url":null,"abstract":"The antioxidant-stabilizer depletion of four 1.5-mm HDPE geomembranes from the same manufacturer each with a different resin and additive package is examined in air and a synthetic municipal solid waste leachate at a range of temperatures (40-95°C) for 7.5 years. Two were formulated for high-temperatures and used polyethylene of raised temperature resistance (PE-RT) resins while two used more conventional HDPE geomembrane formulations. The depletion of protective antioxidants and stabilizers was monitored using standard and high-pressure oxidative induction time (OIT) tests and the notably different depletion times for both OIT tests implied they were detecting different groups of AO-S. Although both PE-RT GMBs showed significantly slower AO-S depletion at 85°C in air compared to the conventional PE GMBs, only one PE-RT GMB maintained this status in 85°C leachate, highlighting the limitation of air aging tests (and importance of fluid immersion tests). The importance of running immersion tests long enough to reveal the residual HP-OIT value is stressed. The roles of stabilizer mobility and solubility in polyethylene and their suspected involvement in residual HP-OIT behavior is also illustrated.","PeriodicalId":12616,"journal":{"name":"Geosynthetics International","volume":" ","pages":""},"PeriodicalIF":4.5,"publicationDate":"2023-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48466663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Moncada, I. P. Damians, S. Olivella, R. Bathurst
The role of temperature and relative humidity on long-term mechanical and chemical degradation of polyester fibres due to hydrolysis and creep is well documented. This study presents the results of a thermo-hydraulic 2D finite-element model used to estimate the magnitude and distribution of in-situ temperature, relative humidity, and degree of saturation in the backfill of reinforced soil walls (RSWs) due to changes in atmospheric boundary conditions. Boundary conditions for in-air temperature, relative humidity and daily precipitation were taken from weather databases for continental, Mediterranean, desert, and tropical climates. Scenarios with different water tables, and permeable or impermeable zones around the reinforced soil zone were analyzed. Numerical outcomes show that mean in-soil temperature values can be related to the mean annual atmospheric value for each geographical location, with relevant fluctuations limited to the first 3 meters of distance from the vertical and horizontal boundaries. In-soil relative humidity values depended on the climate dataset and the permeability of the zones adjacent to the reinforced soil. The results of this study and lessons learned are a valuable precursor for future studies of coupled thermo-hydro-mechanical modelling of polyester geosynthetic RSWs under in-situ operational conditions.
{"title":"Thermo-hydraulic numerical modelling of in-soil conditions in reinforced soil walls","authors":"A. Moncada, I. P. Damians, S. Olivella, R. Bathurst","doi":"10.1680/jgein.23.00026","DOIUrl":"https://doi.org/10.1680/jgein.23.00026","url":null,"abstract":"The role of temperature and relative humidity on long-term mechanical and chemical degradation of polyester fibres due to hydrolysis and creep is well documented. This study presents the results of a thermo-hydraulic 2D finite-element model used to estimate the magnitude and distribution of in-situ temperature, relative humidity, and degree of saturation in the backfill of reinforced soil walls (RSWs) due to changes in atmospheric boundary conditions. Boundary conditions for in-air temperature, relative humidity and daily precipitation were taken from weather databases for continental, Mediterranean, desert, and tropical climates. Scenarios with different water tables, and permeable or impermeable zones around the reinforced soil zone were analyzed. Numerical outcomes show that mean in-soil temperature values can be related to the mean annual atmospheric value for each geographical location, with relevant fluctuations limited to the first 3 meters of distance from the vertical and horizontal boundaries. In-soil relative humidity values depended on the climate dataset and the permeability of the zones adjacent to the reinforced soil. The results of this study and lessons learned are a valuable precursor for future studies of coupled thermo-hydro-mechanical modelling of polyester geosynthetic RSWs under in-situ operational conditions.","PeriodicalId":12616,"journal":{"name":"Geosynthetics International","volume":" ","pages":""},"PeriodicalIF":4.5,"publicationDate":"2023-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47252895","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper provides insight into the causes of post-peak strength loss for textured geomembrane (GMX) and nonwoven geotextile (NGT) interfaces. The NGT can be part of a geosynthetic drainage composite (GDC) or a stand-alone NGT. The study used ring shear tests where one of the two interface materials was replaced after reaching a residual strength condition and restarting the test to measure the change in interface strength. The interface strength loss from peak to large displacement (LD) strength primarily comes from three mechanisms: (1) geomembrane wear, (2) breakage and combing of fibers in the NGT, and reduction of the hook and loop effect between GMX asperities and fibers of the NGT. The source of interface strength loss from LD strength to the residual value mainly comes from breakage and continuous combing of NGT fibers parallel to the direction of shear in ring shear tests. Scanning electron microscope photographs of the GMX and NGT before and after shearing confirm wear and smoothing of GMX asperities and the combing of NGT fibers in the direction of shear.
{"title":"GMX/GDC strength loss mechanisms","authors":"J. Lin, T. Stark, A. Idries, S. Choi","doi":"10.1680/jgein.22.00375","DOIUrl":"https://doi.org/10.1680/jgein.22.00375","url":null,"abstract":"This paper provides insight into the causes of post-peak strength loss for textured geomembrane (GMX) and nonwoven geotextile (NGT) interfaces. The NGT can be part of a geosynthetic drainage composite (GDC) or a stand-alone NGT. The study used ring shear tests where one of the two interface materials was replaced after reaching a residual strength condition and restarting the test to measure the change in interface strength. The interface strength loss from peak to large displacement (LD) strength primarily comes from three mechanisms: (1) geomembrane wear, (2) breakage and combing of fibers in the NGT, and reduction of the hook and loop effect between GMX asperities and fibers of the NGT. The source of interface strength loss from LD strength to the residual value mainly comes from breakage and continuous combing of NGT fibers parallel to the direction of shear in ring shear tests. Scanning electron microscope photographs of the GMX and NGT before and after shearing confirm wear and smoothing of GMX asperities and the combing of NGT fibers in the direction of shear.","PeriodicalId":12616,"journal":{"name":"Geosynthetics International","volume":"835 ","pages":""},"PeriodicalIF":4.5,"publicationDate":"2023-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41280225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Experiments are conducted to investigate leakage through circular GMB holes overlain and underlain by both tailings with various hole diameters and GMB thicknesses. Finite element analyses are performed to explore the effect of hydraulic conductivities (k) of subgrade (underliner) and tailings above the GMB (overliner) on water head contours dissipation. Analytical solution is developed for predicting leakage through circular GMB hole overlain and underlain by both tailings. Results show that the effect of subgrade on leakage is highly dependent on the ratio of k between the underliner and the overliner. If the ratio > 100, no head loss occurs in the subgrade; if the ratio < 0.01, all the head loss occurs in the subgrade. With the deposition of fines from overliner into subgrade, a low permeable filter cake is formed on the subgrade surface, notably increasing the impact of underliner on leakage. With the increasing ratio of k between underliner and overliner from 0.01, 0.1, 1, 10, and to 100, the ratio of leakage relative to a highly permeable subgrade increases from 0.01, 0.1, 0.56, 0.93, and to 1. An intimate interface contact can be achieved when the GMB is underlain by silty sand tailings as subgrade (foundation) material.
{"title":"Leakage through a circular geomembrane hole overlain and underlain by silty sand tailings","authors":"J. Fan, R. Rowe","doi":"10.1680/jgein.23.00028","DOIUrl":"https://doi.org/10.1680/jgein.23.00028","url":null,"abstract":"Experiments are conducted to investigate leakage through circular GMB holes overlain and underlain by both tailings with various hole diameters and GMB thicknesses. Finite element analyses are performed to explore the effect of hydraulic conductivities (k) of subgrade (underliner) and tailings above the GMB (overliner) on water head contours dissipation. Analytical solution is developed for predicting leakage through circular GMB hole overlain and underlain by both tailings. Results show that the effect of subgrade on leakage is highly dependent on the ratio of k between the underliner and the overliner. If the ratio > 100, no head loss occurs in the subgrade; if the ratio < 0.01, all the head loss occurs in the subgrade. With the deposition of fines from overliner into subgrade, a low permeable filter cake is formed on the subgrade surface, notably increasing the impact of underliner on leakage. With the increasing ratio of k between underliner and overliner from 0.01, 0.1, 1, 10, and to 100, the ratio of leakage relative to a highly permeable subgrade increases from 0.01, 0.1, 0.56, 0.93, and to 1. An intimate interface contact can be achieved when the GMB is underlain by silty sand tailings as subgrade (foundation) material.","PeriodicalId":12616,"journal":{"name":"Geosynthetics International","volume":" ","pages":""},"PeriodicalIF":4.5,"publicationDate":"2023-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48764165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Xie, J. Wu, L. Zhan, A. Bouazza, Y. Shi, Y. Chen, J. Lan
This paper presents a design method for liner systems of municipal solid waste (MSW) landfills with high leachate heads based on the breakthrough time of an indicative contaminant (Chloride). The performance of liner systems with varying thicknesses of compacted clay liner and attenuation layer was assessed. The single composite liner consisting of a geomembrane and a 0.75-thickness compacted clay liner can meet the 50-year breakthrough time requirement of the liner system for cases with the thickness of the attenuation layer > 3m and the average height of waste HD < 60 m. The double liner system consisting of two geomembranes with one single 0.3m-thickness compacted clay liner, as proposed in the Chinese landfill standards, cannot meet the 50-year breakthrough time requirement of the liner system, especially for large-scale landfills (e.g., HD > 60 m). The double composite liner with two composite liners consisting of a geomembrane and a 0.3m-thickness compacted clay liner can be used for a landfill with an average height of over 60 m. Different liner systems for other cases with different average design heights of waste and the thickness of the attenuation layer were proposed. They can be easily used for MSW landfills with high leachate heads.
{"title":"Breakthrough time assessment of liner system for MSW landfills with high leachate heads","authors":"H. Xie, J. Wu, L. Zhan, A. Bouazza, Y. Shi, Y. Chen, J. Lan","doi":"10.1680/jgein.23.00052","DOIUrl":"https://doi.org/10.1680/jgein.23.00052","url":null,"abstract":"This paper presents a design method for liner systems of municipal solid waste (MSW) landfills with high leachate heads based on the breakthrough time of an indicative contaminant (Chloride). The performance of liner systems with varying thicknesses of compacted clay liner and attenuation layer was assessed. The single composite liner consisting of a geomembrane and a 0.75-thickness compacted clay liner can meet the 50-year breakthrough time requirement of the liner system for cases with the thickness of the attenuation layer > 3m and the average height of waste HD < 60 m. The double liner system consisting of two geomembranes with one single 0.3m-thickness compacted clay liner, as proposed in the Chinese landfill standards, cannot meet the 50-year breakthrough time requirement of the liner system, especially for large-scale landfills (e.g., HD > 60 m). The double composite liner with two composite liners consisting of a geomembrane and a 0.3m-thickness compacted clay liner can be used for a landfill with an average height of over 60 m. Different liner systems for other cases with different average design heights of waste and the thickness of the attenuation layer were proposed. They can be easily used for MSW landfills with high leachate heads.","PeriodicalId":12616,"journal":{"name":"Geosynthetics International","volume":" ","pages":""},"PeriodicalIF":4.5,"publicationDate":"2023-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47542232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Xiao, K. Wang, L. Xue, Z. Liu, Y. Bai, S. Sun, F. Yang
The dynamic stresses in many subgrades for old railways exceed the bearing capacity of the fillers. The geocell has been used to reinforce weak subgrades and achieve a quick attenuation in the dynamic stress. In this study, a series of field tests were conducted to investigate the dynamic stress attenuation characteristics in a weak subgrade reinforced with a geocell. A coupled finite element-discrete element model was developed to analyze the mechanism of the stress attenuation from a multiscale perspective. The results indicated that increasing the geocell height or decreasing the weld distance resulted in an increase in the attenuation rate. There was a threshold for the weld distance, below which its impact on the stress attenuation rate became negligible. When the weld distance was small, the dynamic stress attenuation was attributed to the geocell induced lateral confinement for the infilled soil. With the weld distance increasing, the deformation of the geocell increased and the membrane effect was further mobilized, which contributed to the dynamic stress attenuation. Based on the field test and numerical results, a design method was proposed to determine the reinforcement parameters of geocell-reinforced subgrade, aimed at improving dynamic stress attenuation and preventing subgrade distress.
{"title":"Dynamic stress attenuation characteristics of geocell-reinforced railway subgrade","authors":"J. Xiao, K. Wang, L. Xue, Z. Liu, Y. Bai, S. Sun, F. Yang","doi":"10.1680/jgein.23.00030","DOIUrl":"https://doi.org/10.1680/jgein.23.00030","url":null,"abstract":"The dynamic stresses in many subgrades for old railways exceed the bearing capacity of the fillers. The geocell has been used to reinforce weak subgrades and achieve a quick attenuation in the dynamic stress. In this study, a series of field tests were conducted to investigate the dynamic stress attenuation characteristics in a weak subgrade reinforced with a geocell. A coupled finite element-discrete element model was developed to analyze the mechanism of the stress attenuation from a multiscale perspective. The results indicated that increasing the geocell height or decreasing the weld distance resulted in an increase in the attenuation rate. There was a threshold for the weld distance, below which its impact on the stress attenuation rate became negligible. When the weld distance was small, the dynamic stress attenuation was attributed to the geocell induced lateral confinement for the infilled soil. With the weld distance increasing, the deformation of the geocell increased and the membrane effect was further mobilized, which contributed to the dynamic stress attenuation. Based on the field test and numerical results, a design method was proposed to determine the reinforcement parameters of geocell-reinforced subgrade, aimed at improving dynamic stress attenuation and preventing subgrade distress.","PeriodicalId":12616,"journal":{"name":"Geosynthetics International","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135903223","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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