In recent years, local scour has occurred on the pier foundations of river bridges during heavy rain and river flooding, often resulting in bridge collapse. This study focused on the characteristic displacement, called “delayed displacement”, of the river bridge pier where the critical displacement of the piers was first observed several days after the flood when the train passed and not immediately after the flood. The authors hypothesized that one of the possible reasons for the delayed displacement is the suffusion of the supporting ground during the flood, followed by a compressive behavior due to the collapse of the soil skeleton under repeated traffic loads. Accordingly, this study performed erosion tests simulating flood and cyclic loading tests simulating train passage using a triaxial test apparatus to check the validity of this hypothesis. In some test cases, suffusion without any deformation occurred in the erosion test but deformed in the cyclic loading test just after the erosion test. This behavior matches the behavior of delayed displacement. It was also suggested that the risk of the delayed displacement becomes high when the soil skeleton was assumed to primarily comprise fine particles, and the void ratio and hydraulic gradient were high.
{"title":"Factors Influencing Suffusion-Induced Delayed Displacement of River Bridge Piers","authors":"Yoshihiro Nishio, Kenji Watanabe","doi":"10.1139/cgj-2023-0484","DOIUrl":"https://doi.org/10.1139/cgj-2023-0484","url":null,"abstract":"In recent years, local scour has occurred on the pier foundations of river bridges during heavy rain and river flooding, often resulting in bridge collapse. This study focused on the characteristic displacement, called “delayed displacement”, of the river bridge pier where the critical displacement of the piers was first observed several days after the flood when the train passed and not immediately after the flood. The authors hypothesized that one of the possible reasons for the delayed displacement is the suffusion of the supporting ground during the flood, followed by a compressive behavior due to the collapse of the soil skeleton under repeated traffic loads. Accordingly, this study performed erosion tests simulating flood and cyclic loading tests simulating train passage using a triaxial test apparatus to check the validity of this hypothesis. In some test cases, suffusion without any deformation occurred in the erosion test but deformed in the cyclic loading test just after the erosion test. This behavior matches the behavior of delayed displacement. It was also suggested that the risk of the delayed displacement becomes high when the soil skeleton was assumed to primarily comprise fine particles, and the void ratio and hydraulic gradient were high.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141002682","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Polymers have been shown to enhance the resistance of swelling clay soils to desiccation cracking, a critical property in engineering applications, particularly in waste containment facilities. However, the microscopic and macroscopic mechanisms driving this improvement remain poorly understood. Additionally, the influence of different mixing methods on these mechanisms is not well-established. While dry mixing is more convenient for onsite implementation, wet mixing offers intercalation between clay and polymer, resulting in potentially more durable stabilization outcomes. In this paper, key properties related to desiccation cracking of a polymer-clay mixture were measured. The mixture was synthesised by amending Na-bentonite with sodium carboxymethyl cellulose (Na-CMC) using dry and wet mixing. Soil water retention characteristics curves (SWCC), swelling and shrinkage potential, tensile strength, and pore size distribution by mercury intrusion porosimetry (MIP) were measured for both mixtures and untreated bentonite. Compared to pure bentonite, mixtures were found to have slightly reduced air-entry values, significantly lower swelling and shrinkage potentials and higher tensile strengths. In all experiments, dry mixing exhibited superior performance compared to wet mixing. MIP analysis of the amended mixtures revealed a more porous structure when compared to untreated bentonite.
{"title":"Enhanced Resistance to Desiccation Cracking of Polymer-Bentonite Mixtures: An Experimental Investigation of Underlying Mechanisms","authors":"S. Taheri, Abbas Elzein","doi":"10.1139/cgj-2023-0388","DOIUrl":"https://doi.org/10.1139/cgj-2023-0388","url":null,"abstract":"Polymers have been shown to enhance the resistance of swelling clay soils to desiccation cracking, a critical property in engineering applications, particularly in waste containment facilities. However, the microscopic and macroscopic mechanisms driving this improvement remain poorly understood. Additionally, the influence of different mixing methods on these mechanisms is not well-established. While dry mixing is more convenient for onsite implementation, wet mixing offers intercalation between clay and polymer, resulting in potentially more durable stabilization outcomes. In this paper, key properties related to desiccation cracking of a polymer-clay mixture were measured. The mixture was synthesised by amending Na-bentonite with sodium carboxymethyl cellulose (Na-CMC) using dry and wet mixing. Soil water retention characteristics curves (SWCC), swelling and shrinkage potential, tensile strength, and pore size distribution by mercury intrusion porosimetry (MIP) were measured for both mixtures and untreated bentonite. Compared to pure bentonite, mixtures were found to have slightly reduced air-entry values, significantly lower swelling and shrinkage potentials and higher tensile strengths. In all experiments, dry mixing exhibited superior performance compared to wet mixing. MIP analysis of the amended mixtures revealed a more porous structure when compared to untreated bentonite.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141004844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An important drawback of the hypoplastic model is the inaccurate prediction of the sand behavior under undrained monotonic loading conditions. The model is not able to reproduce the limited liquefaction type response widely observed in undrained tests on loose sand, and it often underestimates the initial stiffness and hardening rate of sand during the shearing. To address these issues, three novel modifications are introduced into a basic hypoplastic model to enhance its undrained predictive capability. Firstly, a new factor is added to the nonlinear term of the model, allowing the simulation of a purely elastic response at the beginning of loading. By doing so, the model can accurately capture the initial stiffness and undrained effective stress path of sand. Secondly, the characterized void ratios are related to an evolving state variable, enabling the model to reasonably reproduce the limited flow response and quasi-steady state. Furthermore, a new term is incorporated into the deviatoric part of the strain rate to adjust the hardening rate of the model. The model performance for undrained loading is significantly improved through the above modifications, as evidenced by the good agreement between simulation results and experimental data for tests with varying densities and confining pressures.
{"title":"Improvement of a hypoplastic model for sand under undrained loading conditions","authors":"Dong Liao, Xunjian Hu, Shun Wang, Chao Zhou","doi":"10.1139/cgj-2023-0670","DOIUrl":"https://doi.org/10.1139/cgj-2023-0670","url":null,"abstract":"An important drawback of the hypoplastic model is the inaccurate prediction of the sand behavior under undrained monotonic loading conditions. The model is not able to reproduce the limited liquefaction type response widely observed in undrained tests on loose sand, and it often underestimates the initial stiffness and hardening rate of sand during the shearing. To address these issues, three novel modifications are introduced into a basic hypoplastic model to enhance its undrained predictive capability. Firstly, a new factor is added to the nonlinear term of the model, allowing the simulation of a purely elastic response at the beginning of loading. By doing so, the model can accurately capture the initial stiffness and undrained effective stress path of sand. Secondly, the characterized void ratios are related to an evolving state variable, enabling the model to reasonably reproduce the limited flow response and quasi-steady state. Furthermore, a new term is incorporated into the deviatoric part of the strain rate to adjust the hardening rate of the model. The model performance for undrained loading is significantly improved through the above modifications, as evidenced by the good agreement between simulation results and experimental data for tests with varying densities and confining pressures.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141009708","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Cement soil stabilization is widely used in civil engineering to improve the performance of soils subjected to freeze-thaw (F-T), wet-dry (W-D), and sulfate attack (SA). Due to the negative impacts associated with manufacturing cement, the development of eco-friendly and sustainable additives is highly desirable. Coal-derived char is cost-effective and byproduct of coal pyrolysis process. In this study, the influence of coal char on mineralogical, microstructural, physical, and mechanical properties of cement stabilized soils (with cement contents of 0-20% and char contents of 0-30%) subjected to F-T cycles, W-D cycles, and SA is investigated. Compared to cement stabilized soils, char-cement stabilized soils exhibit up to 60.8% fewer volume changes during F-T cycles and 31.6% fewer during W-D cycles. The compressive strength of char-cement stabilized soils with cement contents of 5%, 10%, and 20% are on average 7.9%, 17.6%, and 11.0%, respectively higher than that of cement stabilized soil subjected to F-T cycles, W-D cycles, or SA. The inclusion of char promotes cement hydration and results in the formation of more amorphous hydration products that fill voids or cover soil minerals. The findings indicate the promising potential of coal char in enhancing the soil performance under a range of challenging environmental conditions.
{"title":"Coal-derived char for durability improvement of cement stabilized soil under freeze-thaw, wet-dry, and sulfate attack","authors":"Hua Yu, Priyanka Joshi, Chooikim Lau, Kam Ng","doi":"10.1139/cgj-2023-0626","DOIUrl":"https://doi.org/10.1139/cgj-2023-0626","url":null,"abstract":"Cement soil stabilization is widely used in civil engineering to improve the performance of soils subjected to freeze-thaw (F-T), wet-dry (W-D), and sulfate attack (SA). Due to the negative impacts associated with manufacturing cement, the development of eco-friendly and sustainable additives is highly desirable. Coal-derived char is cost-effective and byproduct of coal pyrolysis process. In this study, the influence of coal char on mineralogical, microstructural, physical, and mechanical properties of cement stabilized soils (with cement contents of 0-20% and char contents of 0-30%) subjected to F-T cycles, W-D cycles, and SA is investigated. Compared to cement stabilized soils, char-cement stabilized soils exhibit up to 60.8% fewer volume changes during F-T cycles and 31.6% fewer during W-D cycles. The compressive strength of char-cement stabilized soils with cement contents of 5%, 10%, and 20% are on average 7.9%, 17.6%, and 11.0%, respectively higher than that of cement stabilized soil subjected to F-T cycles, W-D cycles, or SA. The inclusion of char promotes cement hydration and results in the formation of more amorphous hydration products that fill voids or cover soil minerals. The findings indicate the promising potential of coal char in enhancing the soil performance under a range of challenging environmental conditions.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141015596","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tian-qi Zhang, Zhenkun Li, Ruikun Wang, Gang Zheng, Huayang Lei, Qi Fan
The stress state of soil may affect the building settlements induced by tunnelling, which, however, has not been well understood. In this study, 3D numerical analyses combined with in-situ measurements were performed to investigate the geostress-associated settlements of a raft-foundation building due to tunnelling in soft ground. Basically, two types of geostress fields were investigated: the first type considered the effect of additional stress generated in the foundation soil (FAS) due to building weight; while in the second type, a sequential twin tunnelling was presumed, and the effect of additional soil stress induced by the first tunnel (TAS) on the building response to the second tunnel was considered. The results indicated that FAS may aggravate the stress release of the foundation soil, and thus gave rise to a larger building settlement or inclination. In the sequential tunnelling process, the effect of TAS can be more complex: when the first tunnel lowered the stress of foundation soil, TAS effect of the first tunnel may help reduce the building settlements induced by the second tunnel; otherwise, it may aggravate building settlements. In addition to TAS effect, the sheltering effect was also found to play an important part in twin tunnelling.
土壤的应力状态可能会影响隧道开挖引起的建筑物沉降，但对这一问题的了解还不够深入。本研究结合三维数值分析和现场测量，研究了在软土地基上开挖隧道造成的筏基建筑与地质应力相关的沉降。基本上，研究了两种类型的地应力场：第一种类型考虑了由于建筑物自重而在地基土中产生的附加应力（FAS）的影响；而在第二种类型中，假定了连续双隧道，并考虑了第一条隧道引起的附加土应力（TAS）对建筑物对第二条隧道响应的影响。结果表明，FAS 可能会加剧地基土的应力释放，从而导致建筑物出现更大的沉降或倾斜。在连续隧道开挖过程中，TAS 的影响可能更为复杂：当第一条隧道降低了地基土的应力时，第一条隧道的 TAS 效应可能有助于减少第二条隧道引起的建筑物沉降；反之，则可能加剧建筑物沉降。除了 TAS 效应外，研究还发现遮挡效应在双线隧道中也发挥着重要作用。
{"title":"Geostress-associated settlements of a raft-foundation building due to shield tunnelling in soft ground","authors":"Tian-qi Zhang, Zhenkun Li, Ruikun Wang, Gang Zheng, Huayang Lei, Qi Fan","doi":"10.1139/cgj-2024-0010","DOIUrl":"https://doi.org/10.1139/cgj-2024-0010","url":null,"abstract":"The stress state of soil may affect the building settlements induced by tunnelling, which, however, has not been well understood. In this study, 3D numerical analyses combined with in-situ measurements were performed to investigate the geostress-associated settlements of a raft-foundation building due to tunnelling in soft ground. Basically, two types of geostress fields were investigated: the first type considered the effect of additional stress generated in the foundation soil (FAS) due to building weight; while in the second type, a sequential twin tunnelling was presumed, and the effect of additional soil stress induced by the first tunnel (TAS) on the building response to the second tunnel was considered. The results indicated that FAS may aggravate the stress release of the foundation soil, and thus gave rise to a larger building settlement or inclination. In the sequential tunnelling process, the effect of TAS can be more complex: when the first tunnel lowered the stress of foundation soil, TAS effect of the first tunnel may help reduce the building settlements induced by the second tunnel; otherwise, it may aggravate building settlements. In addition to TAS effect, the sheltering effect was also found to play an important part in twin tunnelling.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141016529","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Field studies and geothermal modelling shows ground cooling below raised buildings in permafrost regions significantly offsets the ground warming impact of climate warming. For an adfreeze pile, the ground cooling below a raised building improves the capacity relative to pre-construction conditions. Many designers do not take credit for this cooling effect but propose to incorporate thermal mitigation in the design, such as the use of thermopiles. The adaptive adfreeze pile is an innovative concept that accounts for long-term cooling beneath raised buildings and the resulting enhanced pile capacity. The concept entails the installation of a closed ended steel pipe as a conventional adfreeze pile. If future ground temperatures warm above a design threshold, a small diameter thermosyphon could be inserted into the interior of the hollow pile. The retrofitted thermosyphon, if ever required, would passively cool the ground during winter to reduce the mean annual ground temperature and maintain pile capacity. This approach is cost-effective compared to conventional thermopile design and provides greater thermosyphon performance assurances in the long-term. This paper details of the application of this pile design for two, multi-story buildings in Old Crow Yukon, and describes the geothermal background showing its technical feasibility and initial performance data.
{"title":"Development and Performance of an Adaptive Adfreeze Pile","authors":"J. Oswell, Ron Coutts","doi":"10.1139/cgj-2023-0110","DOIUrl":"https://doi.org/10.1139/cgj-2023-0110","url":null,"abstract":"Field studies and geothermal modelling shows ground cooling below raised buildings in permafrost regions significantly offsets the ground warming impact of climate warming. For an adfreeze pile, the ground cooling below a raised building improves the capacity relative to pre-construction conditions. Many designers do not take credit for this cooling effect but propose to incorporate thermal mitigation in the design, such as the use of thermopiles. The adaptive adfreeze pile is an innovative concept that accounts for long-term cooling beneath raised buildings and the resulting enhanced pile capacity. The concept entails the installation of a closed ended steel pipe as a conventional adfreeze pile. If future ground temperatures warm above a design threshold, a small diameter thermosyphon could be inserted into the interior of the hollow pile. The retrofitted thermosyphon, if ever required, would passively cool the ground during winter to reduce the mean annual ground temperature and maintain pile capacity. This approach is cost-effective compared to conventional thermopile design and provides greater thermosyphon performance assurances in the long-term. This paper details of the application of this pile design for two, multi-story buildings in Old Crow Yukon, and describes the geothermal background showing its technical feasibility and initial performance data.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141019080","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kyo-Young Gu, Nghiem Xuan Tran, Jayne M. Han, Kyeong-Sun Kim, Kyung-Won Ham, Sung-Ryul Kim
Realistic simulation of in-situ stresses is an essential consideration in evaluating the bearing capacities of spread foundations. Therefore, this study aimed to investigate the uplift behavior of large spread foundations by performing a series of centrifuge tests. A total of 12 centrifuge test models were constructed considering the variation in the foundation width (3.5–6.5 m), embedment depth ratio (0.67–1.39), and relative density of dry silica sandy soil (40%, 80%). The measured load–displacement curves indicated that the uplift bearing capacity and the corresponding uplift displacement increased with the foundation width at a certain embedment depth ratio. Two sets of empirical equations were proposed by adopting genetic programming to estimate the uplift resistance factor and uplift displacement with consideration of field stress conditions. The proposed equations reasonably matched these parameters under various conditions reported in the literature. Furthermore, a simplified empirical influence zone was proposed on the basis of the measurement of the ground surface displacement. The empirical influence zone, which was a straight line with an inclination angle of ~0.9 times the soil friction angle measured from vertical, could be considered a significant reference for predicting the failure surface of the shallow foundation under uplift loading.
{"title":"Centrifuge study on the uplift behavior of spread foundation for transmission tower in sand","authors":"Kyo-Young Gu, Nghiem Xuan Tran, Jayne M. Han, Kyeong-Sun Kim, Kyung-Won Ham, Sung-Ryul Kim","doi":"10.1139/cgj-2023-0065","DOIUrl":"https://doi.org/10.1139/cgj-2023-0065","url":null,"abstract":"Realistic simulation of in-situ stresses is an essential consideration in evaluating the bearing capacities of spread foundations. Therefore, this study aimed to investigate the uplift behavior of large spread foundations by performing a series of centrifuge tests. A total of 12 centrifuge test models were constructed considering the variation in the foundation width (3.5–6.5 m), embedment depth ratio (0.67–1.39), and relative density of dry silica sandy soil (40%, 80%). The measured load–displacement curves indicated that the uplift bearing capacity and the corresponding uplift displacement increased with the foundation width at a certain embedment depth ratio. Two sets of empirical equations were proposed by adopting genetic programming to estimate the uplift resistance factor and uplift displacement with consideration of field stress conditions. The proposed equations reasonably matched these parameters under various conditions reported in the literature. Furthermore, a simplified empirical influence zone was proposed on the basis of the measurement of the ground surface displacement. The empirical influence zone, which was a straight line with an inclination angle of ~0.9 times the soil friction angle measured from vertical, could be considered a significant reference for predicting the failure surface of the shallow foundation under uplift loading.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140663276","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhiao Gao, Lingwei Kong, Shuangjiao Wang, Gang Wang, Junbiao Yan
This study investigates the infiltration characteristics of expansive soil subjected to drying-wetting cycles under surcharge. Infiltration tests are conducted on undisturbed expansive soil over four drying-wetting cycles. Additionally, the permeability coefficient under loading is determined prior to any drying–wetting cycles. Within the context of this study, the sample heights after drying and after wetting are monitored to determinethe natural swelling and shrinkage deformations. Experimental results show that the infiltration rate decreases asthe presssure increases. The sample’s swelling–shrinkage deformation decreases with each progressive drying–wetting cycle, whereas the infiltration rate consistently increases. The infiltration curve under the drying–wetting cycle can be divided into three stages according to the infiltration characteristics, which is significantly different from the infiltration curve of the sample without the drying–wetting cycle. Moreover, the proposed model can fit the infiltration curves well, and its fitting parameters are described using dimensionless pressure and the number of drying-wetting cycles.The drying of the expansive soil produces cracksthat are advantageous for infiltration. Additionally, the microscopic connection between aggregates reflects changes in the internal structure of the soil during successive drying–wetting cycles. As the number of drying–wetting cycle increases, small particles aggregate into large aggregates, and the contact relationship between the aggregate changes from face–face to point-point contact, reducing the swelling potential and increasing the porosity and infiltration capacity of the soil.
{"title":"The Infiltration characteristics of expansive soil subjected to drying-wetting cycles under surchage","authors":"Zhiao Gao, Lingwei Kong, Shuangjiao Wang, Gang Wang, Junbiao Yan","doi":"10.1139/cgj-2023-0223","DOIUrl":"https://doi.org/10.1139/cgj-2023-0223","url":null,"abstract":"This study investigates the infiltration characteristics of expansive soil subjected to drying-wetting cycles under surcharge. Infiltration tests are conducted on undisturbed expansive soil over four drying-wetting cycles. Additionally, the permeability coefficient under loading is determined prior to any drying–wetting cycles. Within the context of this study, the sample heights after drying and after wetting are monitored to determinethe natural swelling and shrinkage deformations. Experimental results show that the infiltration rate decreases asthe presssure increases. The sample’s swelling–shrinkage deformation decreases with each progressive drying–wetting cycle, whereas the infiltration rate consistently increases. The infiltration curve under the drying–wetting cycle can be divided into three stages according to the infiltration characteristics, which is significantly different from the infiltration curve of the sample without the drying–wetting cycle. Moreover, the proposed model can fit the infiltration curves well, and its fitting parameters are described using dimensionless pressure and the number of drying-wetting cycles.The drying of the expansive soil produces cracksthat are advantageous for infiltration. Additionally, the microscopic connection between aggregates reflects changes in the internal structure of the soil during successive drying–wetting cycles. As the number of drying–wetting cycle increases, small particles aggregate into large aggregates, and the contact relationship between the aggregate changes from face–face to point-point contact, reducing the swelling potential and increasing the porosity and infiltration capacity of the soil.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140697051","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The effect of texturing (co-extrusion using a blowing agent) on the long-term performance of geomembranes immersed in synthetic municipal solid waste (MSW) leachate is examined over an approximately 8-year period. Antioxidant depletion of the textured part is shown to be much faster than that of the smooth edge. Likewise, the degradation in the tensile break properties at 85°C is faster for the textured part than for the smooth edge portion and smooth equivalent. The updated estimates for antioxidant depletion time based on data at four different temperatures (40, 55, 75, and 85°C) over 98 months of data collection are compared with predictions based on 34 months of data and the implications are discussed. Nominal failure was reached at 75°C, and this combined with data at 85°C allows prediction of the time between depletion of Std-OIT and nominal failure at lower temperatures. The effect of salt concentration in incubation fluid on the time to degradation is examined. Finally, the paper comments on the uses of textured versus smooth geomembrane.
{"title":"Long-term Performance of Textured HDPE Geomembranes in Municipal Solid Waste Landfills","authors":"R. K. Rowe, M. Ali, Mohamed S. Morsy","doi":"10.1139/cgj-2024-0024","DOIUrl":"https://doi.org/10.1139/cgj-2024-0024","url":null,"abstract":"The effect of texturing (co-extrusion using a blowing agent) on the long-term performance of geomembranes immersed in synthetic municipal solid waste (MSW) leachate is examined over an approximately 8-year period. Antioxidant depletion of the textured part is shown to be much faster than that of the smooth edge. Likewise, the degradation in the tensile break properties at 85°C is faster for the textured part than for the smooth edge portion and smooth equivalent. The updated estimates for antioxidant depletion time based on data at four different temperatures (40, 55, 75, and 85°C) over 98 months of data collection are compared with predictions based on 34 months of data and the implications are discussed. Nominal failure was reached at 75°C, and this combined with data at 85°C allows prediction of the time between depletion of Std-OIT and nominal failure at lower temperatures. The effect of salt concentration in incubation fluid on the time to degradation is examined. Finally, the paper comments on the uses of textured versus smooth geomembrane.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140730814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Adrien Dimech, Bruno Bussière, LiZhen Cheng, Michel Chouteau, G. Fabien-Ouellet, Nathalie Chevé, Anne Isabelle, Paul B. Wilkinson, Philip Meldrum, Jonathan Chambers
The dynamics of moisture content in cover systems constructed on mining wastes were monitored at the pilot scale using 2D autonomous, remote, and non-invasive time-lapse electrical resistivity tomography combined with conventional point sensors. A methodology was proposed to process the daily hydrogeophysical datasets from 23 m-long instrumented sections of covers with capillary barrier effects (CCBEs) designed to act as oxygen barriers, and covers with low saturated hydraulic conductivity layers (LSHCCs) designed to limit the water infiltration rate. Hydrogeophysical monitoring suggested that CCBEs were able to maintain high degrees of saturation in the moisture-retaining layer throughout the one-year monitoring period, which would make it an efficient oxygen barrier. Larger spatio-temporal changes in moisture content were observed in LSHCCs and most of the low hydraulic conductivity layers remained below 85% saturation, which was attributed to the combined effect of low precipitation, rapid vegetation development, and water percolation through the cover. The methodology proposed in this pilot-scale "proof-of-concept" study allowed the hydrogeological behavior of the cover systems to be monitored in the 23 m-long instrumented sections using continuous geoelectrical data, which demonstrated that this innovative monitoring technique could be useful for geochemical and geotechnical monitoring programs in large-scale mining waste storage facilities.
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