Existing criteria for assessing internal erosion usually are based on static loading and the effect of cyclic load is not considered. Additionally, there are limited studies to examine the particle-size destitution and origin of eroded fine particles. This work presents an experimental investigation that examines the impact of cyclic loading on internal stability through a series of seepage tests. The composition and origin of lost particles are quantitatively studied using particle staining and image recognition techniques. After significant loss of particles, the specimens reach a state of transient equilibrium, resulting in a gradual slowdown of both particle loss rate and average flow velocity. The results indicate that cyclic loading promotes massive particle loss and causes erosion failure of specimens that are considered stable according to existing criteria. The reason is that under cyclic loading, local hydraulic gradients is oscillating, and a larger than average hydraulic gradient may occur, which is responsible for the internal instability. The analysis suggests that existing criteria can provide a reasonable assessment of the relative stabilities of specimens under static loads, but fail to capture the stabilities under cyclic loading conditions.
{"title":"Stability of sandy soils against internal erosion under cyclic loading and quantitatively examination of the composition and origin of eroded particles","authors":"Shaoheng Dai, Xuzhen He, Chenxi Tong, Feng Gao, Sheng Zhang, Daichao Sheng","doi":"10.1139/cgj-2023-0325","DOIUrl":"https://doi.org/10.1139/cgj-2023-0325","url":null,"abstract":"Existing criteria for assessing internal erosion usually are based on static loading and the effect of cyclic load is not considered. Additionally, there are limited studies to examine the particle-size destitution and origin of eroded fine particles. This work presents an experimental investigation that examines the impact of cyclic loading on internal stability through a series of seepage tests. The composition and origin of lost particles are quantitatively studied using particle staining and image recognition techniques. After significant loss of particles, the specimens reach a state of transient equilibrium, resulting in a gradual slowdown of both particle loss rate and average flow velocity. The results indicate that cyclic loading promotes massive particle loss and causes erosion failure of specimens that are considered stable according to existing criteria. The reason is that under cyclic loading, local hydraulic gradients is oscillating, and a larger than average hydraulic gradient may occur, which is responsible for the internal instability. The analysis suggests that existing criteria can provide a reasonable assessment of the relative stabilities of specimens under static loads, but fail to capture the stabilities under cyclic loading conditions.
","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135192885","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 soil-water characteristics curve (SWCC) that is typically measured from laboratory tests is fit using mathematical models that are based on capillary law and used along with the saturated soil properties for predicting the hydro-mechanical behavior of unsaturated soils. Such SWCC models are valid for coarse-grained soils. However, the same models are also extended for modeling the SWCC of fine-grained soils over suction range from 0 to 106 kPa with a correction function. Due to this reason, SWCC models with correction functions have limitations in rigorous analyses of complex thermo-hydro-mechanical-chemo (THMC) behaviors of unsaturated soils, especially in the high suction range. In the present study, correction function is proposed for modeling the SWCC behavior using two widely models based on a theoretical framework extending the principles of thermodynamics. The relationships between the traditional and the proposed correction functions are discussed. Finally, comparisons are provided between the proposed and the traditional correction functions on the SWCC behavior to highlight their differences. In addition, the effects of temperature and salinity on the SWCC with correction functions are also summarized. The proposed correction function is a valuable tool for rigorous analyses and reliable prediction of the complex THMC behaviors of unsaturated soils.
{"title":"Correction Functions for Soil-Water Characteristics Curves Extending the Principles of Thermodynamics","authors":"Yao Li, Sai Vanapalli","doi":"10.1139/cgj-2023-0266","DOIUrl":"https://doi.org/10.1139/cgj-2023-0266","url":null,"abstract":"The soil-water characteristics curve (SWCC) that is typically measured from laboratory tests is fit using mathematical models that are based on capillary law and used along with the saturated soil properties for predicting the hydro-mechanical behavior of unsaturated soils. Such SWCC models are valid for coarse-grained soils. However, the same models are also extended for modeling the SWCC of fine-grained soils over suction range from 0 to 106 kPa with a correction function. Due to this reason, SWCC models with correction functions have limitations in rigorous analyses of complex thermo-hydro-mechanical-chemo (THMC) behaviors of unsaturated soils, especially in the high suction range. In the present study, correction function is proposed for modeling the SWCC behavior using two widely models based on a theoretical framework extending the principles of thermodynamics. The relationships between the traditional and the proposed correction functions are discussed. Finally, comparisons are provided between the proposed and the traditional correction functions on the SWCC behavior to highlight their differences. In addition, the effects of temperature and salinity on the SWCC with correction functions are also summarized. The proposed correction function is a valuable tool for rigorous analyses and reliable prediction of the complex THMC behaviors of unsaturated soils.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135340378","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 performance of asymmetric pit-in-pit excavation supported by diaphragm wall and multi uplift piles in coastal areas has been rarely reported. In this work, case study is conducted to investigate the mechanical characteristics of such excavation. A numerical model is established using the ABAQUS finite element platform, and its effectiveness is evaluated by comparing with the field monitoring data. After evaluation, the effects of uplift piles on excavation-induced deformations are investigated. Results show that the maximum wall deflections (δhm) are 0.02%~0.22% of the excavation depth (He), with the ground surface settlements of less than 0.6%·He and the settlement influence zone extending beyond 4He. As the soil is excavated, the top wall shows outward deformations to the active zone, and the transverse support is under tension. The use of combined diaphragm wall and multi uplift piles reduces the embedment ratio of diaphragm wall to a minimum value of 0.14, and decreases the δhm and rebound of base soil (δvrm) by 42% and 63%, respectively. A design suggestion is proposed for pile diameter (D), pile length (L) and pile spacing (S) to fall within the range of 0.4~0.8 m, 10~20 m and 6D~8D, respectively.
{"title":"Performance of an Asymmetric Pit-in-Pit Excavation Supported by Diaphragm Wall and Multi Uplift Piles System in Coastal Areas","authors":"Ruisong Wang, Hongyuan Dong, Daoxu Shen, Jianfeng Li, Pengpeng Ni, Chenyang Zhao","doi":"10.1139/cgj-2023-0319","DOIUrl":"https://doi.org/10.1139/cgj-2023-0319","url":null,"abstract":"The performance of asymmetric pit-in-pit excavation supported by diaphragm wall and multi uplift piles in coastal areas has been rarely reported. In this work, case study is conducted to investigate the mechanical characteristics of such excavation. A numerical model is established using the ABAQUS finite element platform, and its effectiveness is evaluated by comparing with the field monitoring data. After evaluation, the effects of uplift piles on excavation-induced deformations are investigated. Results show that the maximum wall deflections (δhm) are 0.02%~0.22% of the excavation depth (He), with the ground surface settlements of less than 0.6%·He and the settlement influence zone extending beyond 4He. As the soil is excavated, the top wall shows outward deformations to the active zone, and the transverse support is under tension. The use of combined diaphragm wall and multi uplift piles reduces the embedment ratio of diaphragm wall to a minimum value of 0.14, and decreases the δhm and rebound of base soil (δvrm) by 42% and 63%, respectively. A design suggestion is proposed for pile diameter (D), pile length (L) and pile spacing (S) to fall within the range of 0.4~0.8 m, 10~20 m and 6D~8D, respectively.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135341329","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}
Isabella Novais Silva, Buddhima Indraratna, Thanh Trung Nguyen, Cholachat Rujikiatkamjorn
While the fabric of soil can significantly influence its behaviour, the effect of varying fabric parameters on the subgrade shear response is still not well understood. This study creates soil specimens with different fabrics which are then captured through X-ray microscopic-computed tomography scanning (micro-CT) and quantified by image processing techniques. A comprehensive laboratory investigation is conducted to understand how the soil fabric affects its monotonic and cyclic shear behaviour. The results indicate that the consolidation method creates a more homogeneous fabric with mainly small to medium interconnected pores, whereas the compaction technique creates significantly large and mostly inter-aggregate pores with lower connectivity. In this regard, the consolidated specimens exhibit an elastic-perfectly plastic behaviour, while the compacted specimens show strain-hardening transformation during isotropic monotonic shearing. Under anisotropic conditions, the compacted specimens exhibit a greater strain softening response and excess pore pressure than the consolidated specimens because they have a weaker fabric. Furthermore, the compacted specimens show a larger threshold strain at a smaller critical number of cycles due to the collapse of large pores. These current findings prove the decisive role that soil fabric plays in determining the shear response and failure of subgrade soils.
{"title":"The influence of soil fabric on the monotonic and cyclic shear behaviour of consolidated and compacted specimens","authors":"Isabella Novais Silva, Buddhima Indraratna, Thanh Trung Nguyen, Cholachat Rujikiatkamjorn","doi":"10.1139/cgj-2023-0141","DOIUrl":"https://doi.org/10.1139/cgj-2023-0141","url":null,"abstract":"While the fabric of soil can significantly influence its behaviour, the effect of varying fabric parameters on the subgrade shear response is still not well understood. This study creates soil specimens with different fabrics which are then captured through X-ray microscopic-computed tomography scanning (micro-CT) and quantified by image processing techniques. A comprehensive laboratory investigation is conducted to understand how the soil fabric affects its monotonic and cyclic shear behaviour. The results indicate that the consolidation method creates a more homogeneous fabric with mainly small to medium interconnected pores, whereas the compaction technique creates significantly large and mostly inter-aggregate pores with lower connectivity. In this regard, the consolidated specimens exhibit an elastic-perfectly plastic behaviour, while the compacted specimens show strain-hardening transformation during isotropic monotonic shearing. Under anisotropic conditions, the compacted specimens exhibit a greater strain softening response and excess pore pressure than the consolidated specimens because they have a weaker fabric. Furthermore, the compacted specimens show a larger threshold strain at a smaller critical number of cycles due to the collapse of large pores. These current findings prove the decisive role that soil fabric plays in determining the shear response and failure of subgrade soils.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135819096","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}
Several studies have reported substantial increases in the shaft capacity of driven steel piles in the months following installation. This paper investigates factors influencing this time dependence of shaft capacity by conducting a series of field tests on piles and a parallel series of interface shear tests using a newly developed apparatus. The piles and interfaces used in the experiments employ mild steel, stainless steel and galvanised steel, while the ageing periods allowed in the laboratory and field were 1 and 3 years respectively. Chemical analyses of the crusts that developed at the sand-steel interfaces are reported. It is shown that the ageing characteristic of sand-steel friction depends on the relative contributions of interlocking and dilation but is controlled by dilation at the crust-sand interface adjacent to the shaft of a driven pile. There is no gain in shaft friction with time in dry sand or for piles with non-reactive steel. The operational friction angle for mild steel piles in moist or saturated sand is the soil-soil friction angle.
{"title":"The role of physicochemical processes in ageing of shaft friction of driven steel piles in sand","authors":"Eduardo Bittar, B.M. Lehane, Hao Zheng","doi":"10.1139/cgj-2022-0639","DOIUrl":"https://doi.org/10.1139/cgj-2022-0639","url":null,"abstract":"Several studies have reported substantial increases in the shaft capacity of driven steel piles in the months following installation. This paper investigates factors influencing this time dependence of shaft capacity by conducting a series of field tests on piles and a parallel series of interface shear tests using a newly developed apparatus. The piles and interfaces used in the experiments employ mild steel, stainless steel and galvanised steel, while the ageing periods allowed in the laboratory and field were 1 and 3 years respectively. Chemical analyses of the crusts that developed at the sand-steel interfaces are reported. It is shown that the ageing characteristic of sand-steel friction depends on the relative contributions of interlocking and dilation but is controlled by dilation at the crust-sand interface adjacent to the shaft of a driven pile. There is no gain in shaft friction with time in dry sand or for piles with non-reactive steel. The operational friction angle for mild steel piles in moist or saturated sand is the soil-soil friction angle.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136019460","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}
Jamie J. Crispin, Abigail H. Bateman, Elia Voyagaki, Alexandra Campbell, George Mylonakis, Malcolm D. Bolton, Paul Joseph Vardanega
This note presents the application of the Mobilisable Strength Design (MSD) method to the monitoring results of the multi-propped excavation in the south area of the British Library Euston, constructed in a highly overconsolidated stiff clay deposit. The MSD method is an energy-based approach (a non-linear finite-element method for a single-degree-of-freedom soil-wall system) introduced to develop a simplified design methodology that satisfies both ultimate and serviceability limit states. Wall displacement predictions based on the MSD method are compared with considerable field monitoring data. The sensitivity of the method to reasonable variations in input parameters is considered. A spreadsheet and python code demonstrating the MSD analysis from this paper are provided in the Online Supplement alongside details of the mathematical formulation.
{"title":"MSD applied to the construction of the British Library basement: a multi-stage excavation in London Clay","authors":"Jamie J. Crispin, Abigail H. Bateman, Elia Voyagaki, Alexandra Campbell, George Mylonakis, Malcolm D. Bolton, Paul Joseph Vardanega","doi":"10.1139/cgj-2023-0238","DOIUrl":"https://doi.org/10.1139/cgj-2023-0238","url":null,"abstract":"This note presents the application of the Mobilisable Strength Design (MSD) method to the monitoring results of the multi-propped excavation in the south area of the British Library Euston, constructed in a highly overconsolidated stiff clay deposit. The MSD method is an energy-based approach (a non-linear finite-element method for a single-degree-of-freedom soil-wall system) introduced to develop a simplified design methodology that satisfies both ultimate and serviceability limit states. Wall displacement predictions based on the MSD method are compared with considerable field monitoring data. The sensitivity of the method to reasonable variations in input parameters is considered. A spreadsheet and python code demonstrating the MSD analysis from this paper are provided in the Online Supplement alongside details of the mathematical formulation.
","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136103644","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}
In this paper, a generalized hypoplastic constitutive model for unsaturated soils based on the work of Fuentes and Triantafyllidis [2013] is presented. The constitutive model is formulated in terms of effective stresses, degree of saturation and suction. The main feature of the model is a Limiting Surface (LS) which describes the maximum achievable void ratio as a function of mean effective stress and degree of saturation. The LS allows to capture the wetting-induced collapse of initially unsaturated soils. The performance of the proposed model is demonstrated by backcalculation of a well-documented experimental study on over 30 samples of compacted Pearl clay by Sun et al. [2004] under isotropic as well as triaxial loading conditions. For this purpose, the proposed model is coupled with a hypoplastic model for the soil-water retention curve, which interrelates the effective degree of saturation with the suction and the void ratio.
{"title":"Generalized hydro-mechanically coupled hypoplastic constitutive model for unsaturated collapsible soils","authors":"Merita Tafili, Jan Machacek","doi":"10.1139/cgj-2022-0633","DOIUrl":"https://doi.org/10.1139/cgj-2022-0633","url":null,"abstract":"In this paper, a generalized hypoplastic constitutive model for unsaturated soils based on the work of Fuentes and Triantafyllidis [2013] is presented. The constitutive model is formulated in terms of effective stresses, degree of saturation and suction. The main feature of the model is a Limiting Surface (LS) which describes the maximum achievable void ratio as a function of mean effective stress and degree of saturation. The LS allows to capture the wetting-induced collapse of initially unsaturated soils. The performance of the proposed model is demonstrated by backcalculation of a well-documented experimental study on over 30 samples of compacted Pearl clay by Sun et al. [2004] under isotropic as well as triaxial loading conditions. For this purpose, the proposed model is coupled with a hypoplastic model for the soil-water retention curve, which interrelates the effective degree of saturation with the suction and the void ratio.
","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136234406","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 multi-line anchor achieves the ‘anchor sharing’ goal by allowing multiple floating devices to be moored, such that the total number of anchors in a floating device array can be reduced significantly. This study proposes a dynamically installed anchor with the potential of resisting uplift loads from varied directions. The multi-line anchor is dynamically installed with the aid of a booster. The installation performance of the hybrid anchor (i.e. multi-line anchor + booster) is first examined by field tests. Then finite-element analyses are performed to investigate the uplift capacity of the anchor under V-H-M-T combined loading conditions. Based on the numerical results, yield envelopes are established for assessing the ultimate bearing capacity of the anchor. Additionally, model tests are conducted to quantitatively study the installation and set-up effects on the uplift capacity of the anchor, indicating the vertical and torque capacities are sensitive to the installation effect. Finally, a design framework is proposed to assess the stability of the multi-line anchor under combined loading conditions.
{"title":"Installation and capacity performance of multi-line dynamically installed anchors","authors":"Jun Liu, Yunfei Li, Xinshuai Guo, Congcong Han","doi":"10.1139/cgj-2022-0623","DOIUrl":"https://doi.org/10.1139/cgj-2022-0623","url":null,"abstract":"The multi-line anchor achieves the ‘anchor sharing’ goal by allowing multiple floating devices to be moored, such that the total number of anchors in a floating device array can be reduced significantly. This study proposes a dynamically installed anchor with the potential of resisting uplift loads from varied directions. The multi-line anchor is dynamically installed with the aid of a booster. The installation performance of the hybrid anchor (i.e. multi-line anchor + booster) is first examined by field tests. Then finite-element analyses are performed to investigate the uplift capacity of the anchor under V-H-M-T combined loading conditions. Based on the numerical results, yield envelopes are established for assessing the ultimate bearing capacity of the anchor. Additionally, model tests are conducted to quantitatively study the installation and set-up effects on the uplift capacity of the anchor, indicating the vertical and torque capacities are sensitive to the installation effect. Finally, a design framework is proposed to assess the stability of the multi-line anchor under combined loading conditions.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136234248","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}
In this study, a hypoplastic model is developed to describe the mechanical behaviors of cemented sand under both monotonic and cyclic loading conditions. A state variable is proposed to qualify the bonding strength. This variable is incorporated into the model to reflect the influence of cementation on the strength, stiffness, and dilatancy of sand. Bonding degradation is considered by allowing the state variable to evolve during deformation. A simple evolution is used with vanishing bonding strength for large deformation. The void ratio and friction angle in the critical state are related to the initial cementation. The model is subsequently extended to account for cyclic loading by incorporating the intergranular strain, fabric change effect, and semifluidized state. The capability of the model is demonstrated by simulating the behavior of cemented sand under both monotonic and cyclic loading conditions.
{"title":"A hypoplastic model for cemented sand under monotonic and cyclic loading","authors":"Dong Liao, Zhongxuan Yang, Shun Wang, Wei Wu","doi":"10.1139/cgj-2023-0079","DOIUrl":"https://doi.org/10.1139/cgj-2023-0079","url":null,"abstract":"In this study, a hypoplastic model is developed to describe the mechanical behaviors of cemented sand under both monotonic and cyclic loading conditions. A state variable is proposed to qualify the bonding strength. This variable is incorporated into the model to reflect the influence of cementation on the strength, stiffness, and dilatancy of sand. Bonding degradation is considered by allowing the state variable to evolve during deformation. A simple evolution is used with vanishing bonding strength for large deformation. The void ratio and friction angle in the critical state are related to the initial cementation. The model is subsequently extended to account for cyclic loading by incorporating the intergranular strain, fabric change effect, and semifluidized state. The capability of the model is demonstrated by simulating the behavior of cemented sand under both monotonic and cyclic loading conditions.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135265837","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}
Aria Tingxian Zhang, Jeff G. Bain, Adrienne Schmall, Carol J. Ptacek, David Blowes
This study presents the field performance of a five-layer composite cover to mitigate acid mine drainage in legacy sulfide tailings in northern Ontario, Canada. Installed in 2008, this cover comprised sand, clay, geosynthetic clay liner, sand, and waste rock layers. To evaluate the effectiveness of the cover in reducing water and oxygen ingress, groundwater and vadose zone hydrological characterization, stable water isotope analysis, pore-gas measurements, oxygen flux calculations, and variably saturated flow modelling were conducted. Results indicate that the clay layer stayed nearly saturated in the spring, fall, and winter, but temporary desiccation occurred during the summer. Compared to uncovered tailings, the cover significantly lowered diffusive oxygen flux. In the summer, fall, and winter, the capillary barrier effect of the cover functioned effectively and inhibited percolation. Atmospheric pore-gas oxygen concentrations at one out of three monitoring locations indicate potential cover imperfections that enabled oxygen transport into the tailings. In the spring and early summer, snowmelt infiltration resulted in percolation that compromised the capillary barrier effect, as well as lateral drainage. The resulting increase in water saturation in the cover limited oxygen transport. Despite potential cover imperfections, this composite cover reduced oxygen and water ingress a decade after installation.
{"title":"Seasonal hydrology and gas transport in a composite cover on sulfide tailings","authors":"Aria Tingxian Zhang, Jeff G. Bain, Adrienne Schmall, Carol J. Ptacek, David Blowes","doi":"10.1139/cgj-2022-0606","DOIUrl":"https://doi.org/10.1139/cgj-2022-0606","url":null,"abstract":"This study presents the field performance of a five-layer composite cover to mitigate acid mine drainage in legacy sulfide tailings in northern Ontario, Canada. Installed in 2008, this cover comprised sand, clay, geosynthetic clay liner, sand, and waste rock layers. To evaluate the effectiveness of the cover in reducing water and oxygen ingress, groundwater and vadose zone hydrological characterization, stable water isotope analysis, pore-gas measurements, oxygen flux calculations, and variably saturated flow modelling were conducted. Results indicate that the clay layer stayed nearly saturated in the spring, fall, and winter, but temporary desiccation occurred during the summer. Compared to uncovered tailings, the cover significantly lowered diffusive oxygen flux. In the summer, fall, and winter, the capillary barrier effect of the cover functioned effectively and inhibited percolation. Atmospheric pore-gas oxygen concentrations at one out of three monitoring locations indicate potential cover imperfections that enabled oxygen transport into the tailings. In the spring and early summer, snowmelt infiltration resulted in percolation that compromised the capillary barrier effect, as well as lateral drainage. The resulting increase in water saturation in the cover limited oxygen transport. Despite potential cover imperfections, this composite cover reduced oxygen and water ingress a decade after installation.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135219376","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}
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