Buried cast iron pipelines are susceptible to damage at joints under fault movements. In this paper, a new three-dimensional soil-pipe continuum model for segmented pipelines undergoing fault rupture is introduced, in which both the nonlinear behavior of lead-caulked joints and post-peak softening behavior of dense sand are properly characterized. The rationality of the developed numerical model is validated against experimental results reported in the literature. Parametric analyses indicate that ignoring the strain softening behavior of soil would underestimate the maximum joint rotations, and the parameters of fault-pipe intersection angle, cast iron-lead adhesion, and burial depth play a notable role on the magnitude of joint kinematics. Numerical fault rupture analyses are then conducted for cast iron pipelines with nominal diameters ranging from 900 mm to 1,500 mm. Based on the numerical results, predictive solutions are developed for estimating the maximum axial translations and joint rotations under fault movements. The residuals of the proposed solutions are generally unbiased. The proposed solutions can be used to evaluate the maximum joint kinematics in terms of axial translations and joint rotations for large-diameter cast iron pipelines with lead-caulked joints undergoing strike-slip fault ruptures.
{"title":"Kinematic Responses of Lead-caulked Joints for Cast Iron Pipelines Subjected to Strike-slip Faulting","authors":"Dian-Qing Li, Ning Zhao, Wenqi Du, Zijun Cao","doi":"10.1139/cgj-2023-0191","DOIUrl":"https://doi.org/10.1139/cgj-2023-0191","url":null,"abstract":"Buried cast iron pipelines are susceptible to damage at joints under fault movements. In this paper, a new three-dimensional soil-pipe continuum model for segmented pipelines undergoing fault rupture is introduced, in which both the nonlinear behavior of lead-caulked joints and post-peak softening behavior of dense sand are properly characterized. The rationality of the developed numerical model is validated against experimental results reported in the literature. Parametric analyses indicate that ignoring the strain softening behavior of soil would underestimate the maximum joint rotations, and the parameters of fault-pipe intersection angle, cast iron-lead adhesion, and burial depth play a notable role on the magnitude of joint kinematics. Numerical fault rupture analyses are then conducted for cast iron pipelines with nominal diameters ranging from 900 mm to 1,500 mm. Based on the numerical results, predictive solutions are developed for estimating the maximum axial translations and joint rotations under fault movements. The residuals of the proposed solutions are generally unbiased. The proposed solutions can be used to evaluate the maximum joint kinematics in terms of axial translations and joint rotations for large-diameter cast iron pipelines with lead-caulked joints undergoing strike-slip fault ruptures.","PeriodicalId":505159,"journal":{"name":"Canadian Geotechnical Journal","volume":"385 ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140472366","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Suction caisson is a new offshore wind power foundation structure developed in recent years. Understanding its penetration characteristics is crucial to the successful application. A field test was conducted in the eastern waters of Rudong, Jiangsu Province, China, to investigate the penetration process of suction caisson. The test results demonstrate that suction caisson can penetrate smoothly to a predetermined elevation of seabed soil under the complex environmental loads, such as natural wind and wave currents. The inclination of the caisson is only 0.018° once the penetration process is complete. The pore water pressure at the outer skirt is primarily influenced by the tide level and drainage conditions of the contact soil layer during penetration, and the peak effective interface pressure at the skirt-soil interface decreases by about 46.7% due to negative pressure inside the skirt. Frictional fatigue effects are found at the skirt-soil interfaces. Meanwhile, the seepage reduction and squeezing induced resistance effects at the skirt-soil interface are the leading causes for the different distributions of effective interface pressure between the inner and outer skirts of the caisson. The findings of this study can guide the future penetration of suction caisson under challenging geological circumstances.
{"title":"Penetration Characteristics of Suction Caisson for Offshore Wind Power: A Field Study","authors":"Xun Zhu, Zheng Chen, Yun-Fei Guan, Pengpeng Ni, Yong-Gang Liu, Wen-Xuan Li, Xun Han, Kai-fang Fan","doi":"10.1139/cgj-2023-0265","DOIUrl":"https://doi.org/10.1139/cgj-2023-0265","url":null,"abstract":"Suction caisson is a new offshore wind power foundation structure developed in recent years. Understanding its penetration characteristics is crucial to the successful application. A field test was conducted in the eastern waters of Rudong, Jiangsu Province, China, to investigate the penetration process of suction caisson. The test results demonstrate that suction caisson can penetrate smoothly to a predetermined elevation of seabed soil under the complex environmental loads, such as natural wind and wave currents. The inclination of the caisson is only 0.018° once the penetration process is complete. The pore water pressure at the outer skirt is primarily influenced by the tide level and drainage conditions of the contact soil layer during penetration, and the peak effective interface pressure at the skirt-soil interface decreases by about 46.7% due to negative pressure inside the skirt. Frictional fatigue effects are found at the skirt-soil interfaces. Meanwhile, the seepage reduction and squeezing induced resistance effects at the skirt-soil interface are the leading causes for the different distributions of effective interface pressure between the inner and outer skirts of the caisson. The findings of this study can guide the future penetration of suction caisson under challenging geological circumstances.","PeriodicalId":505159,"journal":{"name":"Canadian Geotechnical Journal","volume":"80 ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140481348","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The normal stress, strain rate, and pore-fluid chemistry significantly influence the large-strain shear response of clays and received great attention for engineering practice. The effect of inundation pressure, consolidation pressure, pH of aqueous solutions, and di-electric on the shear response of kaolin was experimentally investigated. The strain-softening behaviour was observed under normally consolidated (NC) conditions as observed in the past studies on different clays. However, this anomalous shear response with volumetric contraction is not understood. Thus, for the first time, the strain-softening behaviour of NC clays was addressed from an effective stress approach using physico-chemical analysis of kaolin. In this study, the drained shear strength response of NC kaolin was investigated under physico-chemical influence using ring shear tests. A theoretical framework was developed by including micro-mechanism of clay fabric evolution during shear and explicit expressions for electro-chemical forces. The proposed framework provides useful expressions for predicting the shear strength behaviour of kaolin clays, which were validated with experimental data from the present study and literature studies. The new conceptual framework satisfactorily explained the peak and residual shear strength variations under different chemo-mechanical loading for NC conditions. The proposed model adequately predicted the effective stress paths, peak, and residual envelopes in ring shear stress conditions for normally consolidated kaolin soils
{"title":"THEORETICAL FRAMEWORK FOR LARGE-STRAIN SHEAR RESISTANCE OF KAOLIN CLAYS UNDER CHEMO-MECHANICAL LOADINGS","authors":"Ankti Srivastava, T. V. Bharat","doi":"10.1139/cgj-2023-0327","DOIUrl":"https://doi.org/10.1139/cgj-2023-0327","url":null,"abstract":"The normal stress, strain rate, and pore-fluid chemistry significantly influence the large-strain shear response of clays and received great attention for engineering practice. The effect of inundation pressure, consolidation pressure, pH of aqueous solutions, and di-electric on the shear response of kaolin was experimentally investigated. The strain-softening behaviour was observed under normally consolidated (NC) conditions as observed in the past studies on different clays. However, this anomalous shear response with volumetric contraction is not understood. Thus, for the first time, the strain-softening behaviour of NC clays was addressed from an effective stress approach using physico-chemical analysis of kaolin. In this study, the drained shear strength response of NC kaolin was investigated under physico-chemical influence using ring shear tests. A theoretical framework was developed by including micro-mechanism of clay fabric evolution during shear and explicit expressions for electro-chemical forces. The proposed framework provides useful expressions for predicting the shear strength behaviour of kaolin clays, which were validated with experimental data from the present study and literature studies. The new conceptual framework satisfactorily explained the peak and residual shear strength variations under different chemo-mechanical loading for NC conditions. The proposed model adequately predicted the effective stress paths, peak, and residual envelopes in ring shear stress conditions for normally consolidated kaolin soils","PeriodicalId":505159,"journal":{"name":"Canadian Geotechnical Journal","volume":"325 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140482944","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tyler J. Oathes, Ross W. Boulanger, K. Ziotopoulou
A viscoplastic model for representing plastic silts and clays in geotechnical static slope stability applications is presented. The PM4SiltR model builds on the stress ratio-controlled, critical state-based, bounding surface plasticity model PM4Silt and is coded as a dynamic link library for use in the finite difference program FLAC 8.1. PM4SiltR incorporates strain rate-dependent shear strength, stress relaxation, and creep using a consistency approach combined with an internal strain rate and auto-decay process. The model does not include a cap, and as such cannot simulate strain rate-dependent consolidation under increasing overburden stress. Six parameters control the viscous response for PM4SiltR while the parameters controlling the nonviscous components of the response are the same as for PM4Silt. Single element simulations are presented to illustrate the influence of viscoplasticity on the constitutive response in direct simple shear loading and undrained creep. Single element responses are shown to be consistent with observed experimental results. Simulations of a hypothetical tailings dam constructed using the upstream method are performed to illustrate use of PM4SiltR at field scale. Results of field scale simulations show PM4SiltR can model undrained creep and progressive failure leading to delayed slope instability after relatively minor changes in loading conditions at field scale.
{"title":"A viscoplastic constitutive model for plastic silts and clays for static slope stability applications","authors":"Tyler J. Oathes, Ross W. Boulanger, K. Ziotopoulou","doi":"10.1139/cgj-2022-0479","DOIUrl":"https://doi.org/10.1139/cgj-2022-0479","url":null,"abstract":"A viscoplastic model for representing plastic silts and clays in geotechnical static slope stability applications is presented. The PM4SiltR model builds on the stress ratio-controlled, critical state-based, bounding surface plasticity model PM4Silt and is coded as a dynamic link library for use in the finite difference program FLAC 8.1. PM4SiltR incorporates strain rate-dependent shear strength, stress relaxation, and creep using a consistency approach combined with an internal strain rate and auto-decay process. The model does not include a cap, and as such cannot simulate strain rate-dependent consolidation under increasing overburden stress. Six parameters control the viscous response for PM4SiltR while the parameters controlling the nonviscous components of the response are the same as for PM4Silt. Single element simulations are presented to illustrate the influence of viscoplasticity on the constitutive response in direct simple shear loading and undrained creep. Single element responses are shown to be consistent with observed experimental results. Simulations of a hypothetical tailings dam constructed using the upstream method are performed to illustrate use of PM4SiltR at field scale. Results of field scale simulations show PM4SiltR can model undrained creep and progressive failure leading to delayed slope instability after relatively minor changes in loading conditions at field scale.","PeriodicalId":505159,"journal":{"name":"Canadian Geotechnical Journal","volume":"3 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139592682","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ruixiao Zhang, Dongfeng Su, Xing-tao Lin, Hong-Jun Lou, X. Chen
This study evaluates the shadowing effect of existing tunnels on the evolution of soil arching, focusing on the shape of the tunnel (circular and rectangular) through trapdoor experiments. The displacement and shear strain distributions of ground soil resulting from trapdoor movement were estimated using a digital image correlation technique. The results showed that the shadowing effect of the rectangular tunnel was significantly greater than that of the circular tunnel of the same size. The sand above the tunnel was displaced in a double-groove pattern owing to the presence of the tunnel, and the maximum surface settlement occurred between the tunnel boundary and the trapdoor edge. The circular tunnels exhibited consistently higher maximum surface displacements than that in the rectangular tunnels. The shear strain value of soil was lower for the rectangular tunnel case than that for the circular tunnel case. The rectangular tunnels required lesser trapdoor displacement than that of the circular tunnel to obtain the minimum soil arching ratio. The minimum and ultimate soil arching ratios increased as the burial depth ratio increased for both the tunnel shapes. The maximum stress ratio of the tunnel crown was consistently larger for the circular case than for the rectangular case.
{"title":"Shadowing effect of an existing tunnel on the evolution of soil arching: impact of tunnel shape","authors":"Ruixiao Zhang, Dongfeng Su, Xing-tao Lin, Hong-Jun Lou, X. Chen","doi":"10.1139/cgj-2023-0439","DOIUrl":"https://doi.org/10.1139/cgj-2023-0439","url":null,"abstract":"This study evaluates the shadowing effect of existing tunnels on the evolution of soil arching, focusing on the shape of the tunnel (circular and rectangular) through trapdoor experiments. The displacement and shear strain distributions of ground soil resulting from trapdoor movement were estimated using a digital image correlation technique. The results showed that the shadowing effect of the rectangular tunnel was significantly greater than that of the circular tunnel of the same size. The sand above the tunnel was displaced in a double-groove pattern owing to the presence of the tunnel, and the maximum surface settlement occurred between the tunnel boundary and the trapdoor edge. The circular tunnels exhibited consistently higher maximum surface displacements than that in the rectangular tunnels. The shear strain value of soil was lower for the rectangular tunnel case than that for the circular tunnel case. The rectangular tunnels required lesser trapdoor displacement than that of the circular tunnel to obtain the minimum soil arching ratio. The minimum and ultimate soil arching ratios increased as the burial depth ratio increased for both the tunnel shapes. The maximum stress ratio of the tunnel crown was consistently larger for the circular case than for the rectangular case.","PeriodicalId":505159,"journal":{"name":"Canadian Geotechnical Journal","volume":"93 11","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139593289","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yucheng Li, Yonggui Chen, Li Liu, Guoping Zhang, Wei-min Ye, Qiong Wang
This paper presents an experimental protocol developed to prepare highly preferentially oriented montmorillonite thin films, and then to probe with nanoindentation their intrinsic mechanical properties (e.g., Young's modulus and hardness). Such highly parallel oriented clay thin films were prepared by dispersing varying amounts of montmorillonite powder (e.g., 1 to 4 g) in deionized water, followed by drying onto silicon wafers. Results indicate that the thin films possess a laminated fabric with a prominent preferred orientation along the basal (00l) plane. Depth-dependent Young’s modulus and hardness were also observed consistently across different specimens. Specifically, Young's modulus and hardness of 4.33 and 0.19 GPa respectively are found at the indentation depth of 100 nm, equivalent to montmorillonite tactoids consisting of ~80 layers of montmorillonite platelets, respectively.
{"title":"Fabrication and mechanical characterization of highly preferentially oriented montmorillonite thin films","authors":"Yucheng Li, Yonggui Chen, Li Liu, Guoping Zhang, Wei-min Ye, Qiong Wang","doi":"10.1139/cgj-2023-0267","DOIUrl":"https://doi.org/10.1139/cgj-2023-0267","url":null,"abstract":"This paper presents an experimental protocol developed to prepare highly preferentially oriented montmorillonite thin films, and then to probe with nanoindentation their intrinsic mechanical properties (e.g., Young's modulus and hardness). Such highly parallel oriented clay thin films were prepared by dispersing varying amounts of montmorillonite powder (e.g., 1 to 4 g) in deionized water, followed by drying onto silicon wafers. Results indicate that the thin films possess a laminated fabric with a prominent preferred orientation along the basal (00l) plane. Depth-dependent Young’s modulus and hardness were also observed consistently across different specimens. Specifically, Young's modulus and hardness of 4.33 and 0.19 GPa respectively are found at the indentation depth of 100 nm, equivalent to montmorillonite tactoids consisting of ~80 layers of montmorillonite platelets, respectively.","PeriodicalId":505159,"journal":{"name":"Canadian Geotechnical Journal","volume":"30 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139600116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shallow foundations are used in many scenarios to transmit the loads from the lightly loaded superstructures constructed on expansive soil slopes. Infiltration associated with rainfall and snow melt influence both the foundation and the expansive soil behavior, including its slope. However, several research studies that are available in the literature focus on only one of these challenges. The combined influence of infiltration on the performance of the foundation and the slope in cracked expansive soils has not received the attention it deserves in the literature. In this study, the combined performance is evaluated with the aid of a numerical method considering shallow foundations located on the top of an unsaturated expansive cracked surficial soil slope. The influence of the rainfall intensity, rainfall duration, foundation setback distance and foundation loading on the foundation bearing capacity and slope stability were investigated. The numerical results of the study highlight that all the parameters have a significant impact on the foundation-slope failure mechanisms associated with different infiltration conditions.
{"title":"Shallow foundation behavior on an expansive soil slope subjected to different infiltration conditions","authors":"Mengxi Tan, Sai Vanapalli","doi":"10.1139/cgj-2023-0184","DOIUrl":"https://doi.org/10.1139/cgj-2023-0184","url":null,"abstract":"Shallow foundations are used in many scenarios to transmit the loads from the lightly loaded superstructures constructed on expansive soil slopes. Infiltration associated with rainfall and snow melt influence both the foundation and the expansive soil behavior, including its slope. However, several research studies that are available in the literature focus on only one of these challenges. The combined influence of infiltration on the performance of the foundation and the slope in cracked expansive soils has not received the attention it deserves in the literature. In this study, the combined performance is evaluated with the aid of a numerical method considering shallow foundations located on the top of an unsaturated expansive cracked surficial soil slope. The influence of the rainfall intensity, rainfall duration, foundation setback distance and foundation loading on the foundation bearing capacity and slope stability were investigated. The numerical results of the study highlight that all the parameters have a significant impact on the foundation-slope failure mechanisms associated with different infiltration conditions.","PeriodicalId":505159,"journal":{"name":"Canadian Geotechnical Journal","volume":"64 23","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139600413","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Due to the limited land resources in major cities, reclamation becomes an optimal option to solve this issue, unsaturated soil is often involved in these projects, and the hydro-mechanical behaviour of this type of soil significantly are affected by the stress history and time effect. In this study, the overconsolidation ratio (OCR) effect of unsaturated silt under different shearing rates was studied through a series of constant water content tests. The specimens were under an effective confining pressure of 400 kPa. The samples were unloaded to 100 kPa, and 50 kPa to achieve different values of OCRs (4, and 8). The samples with different OCRs were then dried from saturated state to initial suction=100, 200, and 300 kPa via axis-translation, and then sheared at three different rates. The results show that higher strain rates led to a higher degree of saturation during shearing under different OCRs. The shear strength increased with increasing shearing rates while the maximum deviator stress decreased when OCR decreased. Higher OCRs resulted in larger volume change during shearing; similar behaviour was observed for increasing rates.
{"title":"Influence of overconsolidation ratio on hydromechanical behavior of unsaturated silty soil under various shearing rates","authors":"Shengshen Wu, Annan Zhou, Jie Li, Bisheng Wu","doi":"10.1139/cgj-2023-0007","DOIUrl":"https://doi.org/10.1139/cgj-2023-0007","url":null,"abstract":"Due to the limited land resources in major cities, reclamation becomes an optimal option to solve this issue, unsaturated soil is often involved in these projects, and the hydro-mechanical behaviour of this type of soil significantly are affected by the stress history and time effect. In this study, the overconsolidation ratio (OCR) effect of unsaturated silt under different shearing rates was studied through a series of constant water content tests. The specimens were under an effective confining pressure of 400 kPa. The samples were unloaded to 100 kPa, and 50 kPa to achieve different values of OCRs (4, and 8). The samples with different OCRs were then dried from saturated state to initial suction=100, 200, and 300 kPa via axis-translation, and then sheared at three different rates. The results show that higher strain rates led to a higher degree of saturation during shearing under different OCRs. The shear strength increased with increasing shearing rates while the maximum deviator stress decreased when OCR decreased. Higher OCRs resulted in larger volume change during shearing; similar behaviour was observed for increasing rates.","PeriodicalId":505159,"journal":{"name":"Canadian Geotechnical Journal","volume":"51 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139613513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
L. Kabwe, Nicholas A. Beier, G. W. Wilson, Umme Salma Rima, J. D. Scott
The total volume of fluid fine tailings (FFT), reached 1,270 Mm3 in 2019. Extensive research is underway by a number of operators to develop dewatering technologies for oil sand tailings reclamation in order to comply with Directive 085 issued by the Alberta Energy Regulator (AER). A promising technology for the disposal of FFT is to add flocculents and then use thickeners or centrifuges to decrease the water content. Following this treatment, freezing/thawing processes can then be utilized to further dewater the tailings. The effect of flocculation/flyash addition and thickening coupled with freezing/thawing treatments on FFT was investigated by performing large-strain consolidation (LSC) and shear strength tests on the treated flocculated TTs. It was found that flocculation and thickening treatment increases the hydraulic conductivity of the treated TT which will result in the TT consolidating much faster than the untreated TT. The most important benefit of the flyash addition is the increase in shear strength and hydraulic conductivity of the flyash-treated TTs. The benefit of the freezing/thawing treatment processes coupled with flyash treatment is the increase in the compressibility and hydraulic conductivity at effective stresses lower than 100 kPa and void ratios greater than 1.2, respectively. This will facilitate earlier progressive reclamation required to support hydraulic sand capping.
{"title":"Effect of flyash addition to flocculation and freezing and thawing treatment on consolidation of oil sands fluid fine tailings","authors":"L. Kabwe, Nicholas A. Beier, G. W. Wilson, Umme Salma Rima, J. D. Scott","doi":"10.1139/cgj-2021-0165","DOIUrl":"https://doi.org/10.1139/cgj-2021-0165","url":null,"abstract":"The total volume of fluid fine tailings (FFT), reached 1,270 Mm3 in 2019. Extensive research is underway by a number of operators to develop dewatering technologies for oil sand tailings reclamation in order to comply with Directive 085 issued by the Alberta Energy Regulator (AER). A promising technology for the disposal of FFT is to add flocculents and then use thickeners or centrifuges to decrease the water content. Following this treatment, freezing/thawing processes can then be utilized to further dewater the tailings. The effect of flocculation/flyash addition and thickening coupled with freezing/thawing treatments on FFT was investigated by performing large-strain consolidation (LSC) and shear strength tests on the treated flocculated TTs. It was found that flocculation and thickening treatment increases the hydraulic conductivity of the treated TT which will result in the TT consolidating much faster than the untreated TT. The most important benefit of the flyash addition is the increase in shear strength and hydraulic conductivity of the flyash-treated TTs. The benefit of the freezing/thawing treatment processes coupled with flyash treatment is the increase in the compressibility and hydraulic conductivity at effective stresses lower than 100 kPa and void ratios greater than 1.2, respectively. This will facilitate earlier progressive reclamation required to support hydraulic sand capping.","PeriodicalId":505159,"journal":{"name":"Canadian Geotechnical Journal","volume":"125 19","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139613654","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhaoyang Song, Tiantian Ma, Guoqing Cai, Yan Liu, Changfu Wei
A constitutive model of unsaturated soils is developed by incorporating the concept of intergranular stress into the framework of the modified Cam-Clay model. Within this context, the degree of saturation is viewed as an internal state variable, so that the soil-water retention function appears naturally as an evolution equation for the volume fraction of water. The new model not only has a neat structure but also includes fewer material parameters compared to the other models. A new volumetric-hardening law is proposed by taking into account the effect of wetting-induced pore collapse. It is shown that the collapsing void ratio (the current void ratio minus the void ratio at full saturation under the same effective stress) is dominated by the degree of pore air saturation (one minus the degree of water saturation), and practically independent of intergranular pulling forces, highlighting the important effect of soil fabric on the wetting-induced pore collapse. The proposed model is applied to simulate different types of experiments on unsaturated soils subjected to various combined hydraulic and mechanical loadings, showing its capability and diversity in modeling the hydraulic and mechanical behavior of unsaturated soils.
{"title":"An effective stress-based approach to modeling the hydro-mechanical behavior of unsaturated soils","authors":"Zhaoyang Song, Tiantian Ma, Guoqing Cai, Yan Liu, Changfu Wei","doi":"10.1139/cgj-2022-0234","DOIUrl":"https://doi.org/10.1139/cgj-2022-0234","url":null,"abstract":"A constitutive model of unsaturated soils is developed by incorporating the concept of intergranular stress into the framework of the modified Cam-Clay model. Within this context, the degree of saturation is viewed as an internal state variable, so that the soil-water retention function appears naturally as an evolution equation for the volume fraction of water. The new model not only has a neat structure but also includes fewer material parameters compared to the other models. A new volumetric-hardening law is proposed by taking into account the effect of wetting-induced pore collapse. It is shown that the collapsing void ratio (the current void ratio minus the void ratio at full saturation under the same effective stress) is dominated by the degree of pore air saturation (one minus the degree of water saturation), and practically independent of intergranular pulling forces, highlighting the important effect of soil fabric on the wetting-induced pore collapse. The proposed model is applied to simulate different types of experiments on unsaturated soils subjected to various combined hydraulic and mechanical loadings, showing its capability and diversity in modeling the hydraulic and mechanical behavior of unsaturated soils.","PeriodicalId":505159,"journal":{"name":"Canadian Geotechnical Journal","volume":"11 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139613794","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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