Yu Zhong, Guillermo Narsilio, Nikolas Makasis, Luis Villegas
This article presents the thermal and thermo-mechanical responses of a pilot energy wall located in Melbourne, Australia, believed to be one of the first instrumented energy soldier piled walls in the world. The full-scale field thermal and thermo-mechanical conditions of the wall have been monitored during the period of a full-cycle thermal response test (TRT) conducted on a single soldier pile over two months. The monitored pile and ground temperature responses reveal the significance of the thermal condition in the excavated space on the thermal performance of such energy geostructures, which increases complexities in design and analysis. Furthermore, this study reports the profiles of axial strains and induced thermal stresses in the tested soldier pile, demonstrating how the applied thermal load from the TRT influenced the mechanical performance of the pile and wall and how the restrictive action of the support elements controlled the induced conditions. Here we show that soldier pile responds differently from energy piles or borehole heat exchangers, however residual axial strains were minimal and similar to those reported in energy piles foundations due to a thermo-elastic response to the imposed thermal loads and wall rigidity. Finally, the unique experimental dataset is made available for further studies.
{"title":"Field investigation on a pilot energy piled retaining wall","authors":"Yu Zhong, Guillermo Narsilio, Nikolas Makasis, Luis Villegas","doi":"10.1139/cgj-2023-0054","DOIUrl":"https://doi.org/10.1139/cgj-2023-0054","url":null,"abstract":"This article presents the thermal and thermo-mechanical responses of a pilot energy wall located in Melbourne, Australia, believed to be one of the first instrumented energy soldier piled walls in the world. The full-scale field thermal and thermo-mechanical conditions of the wall have been monitored during the period of a full-cycle thermal response test (TRT) conducted on a single soldier pile over two months. The monitored pile and ground temperature responses reveal the significance of the thermal condition in the excavated space on the thermal performance of such energy geostructures, which increases complexities in design and analysis. Furthermore, this study reports the profiles of axial strains and induced thermal stresses in the tested soldier pile, demonstrating how the applied thermal load from the TRT influenced the mechanical performance of the pile and wall and how the restrictive action of the support elements controlled the induced conditions. Here we show that soldier pile responds differently from energy piles or borehole heat exchangers, however residual axial strains were minimal and similar to those reported in energy piles foundations due to a thermo-elastic response to the imposed thermal loads and wall rigidity. Finally, the unique experimental dataset is made available for further studies.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"111 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135691537","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}
Planting vegetation is a sustainable and eco-friendly method for shallow slope stabilization. However, in water-limited regions, this method is facing challenges like retarded vegetation growth, which leads to unprotected soils. Biopolymer, with potentials in both vegetation growth promotion and soil strength enhancement, is therefore tested in this paper with regard to its possibility in assisting soil reinforcement with vegetation through vegetation cultivation and direct shear tests. Both sugar-based and protein-based biopolymers improved water availability to growing plants and nutrient uptake. The most suitable polysaccharide xanthan gum was adopted to further explore the effects of treatment condition (i.e., blending content) and external environment (i.e., precipitation) on the vegetated soil performances. Under a variety of water supply, xanthan gum with a medium blending content of 0.5% (i.e., with respect to dry soil mass) led to the most substantial improvement in the ability to resist shear loading. This indicates that the appropriate dosage of biopolymer used at the initial stage of plant growth, should provide moderate bond strength between soil particles, whilst not impeding root penetration. Supported by the obtained results, biopolymer is suggested to be used in combination with plants for soil reinforcement for the best efficiency.
{"title":"Vegetation growth promotion and overall strength improvement using biopolymers in vegetated soils","authors":"Jing Ni, Zi-Teng Wang, Xueyu Geng","doi":"10.1139/cgj-2022-0049","DOIUrl":"https://doi.org/10.1139/cgj-2022-0049","url":null,"abstract":"Planting vegetation is a sustainable and eco-friendly method for shallow slope stabilization. However, in water-limited regions, this method is facing challenges like retarded vegetation growth, which leads to unprotected soils. Biopolymer, with potentials in both vegetation growth promotion and soil strength enhancement, is therefore tested in this paper with regard to its possibility in assisting soil reinforcement with vegetation through vegetation cultivation and direct shear tests. Both sugar-based and protein-based biopolymers improved water availability to growing plants and nutrient uptake. The most suitable polysaccharide xanthan gum was adopted to further explore the effects of treatment condition (i.e., blending content) and external environment (i.e., precipitation) on the vegetated soil performances. Under a variety of water supply, xanthan gum with a medium blending content of 0.5% (i.e., with respect to dry soil mass) led to the most substantial improvement in the ability to resist shear loading. This indicates that the appropriate dosage of biopolymer used at the initial stage of plant growth, should provide moderate bond strength between soil particles, whilst not impeding root penetration. Supported by the obtained results, biopolymer is suggested to be used in combination with plants for soil reinforcement for the best efficiency.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135826622","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}
Oil sand reservoirs and caprock undergo deformations triggered by pore pressure increases and thermal induced stresses during the steam-assisted-gravity-drainage (SAGD) processes. Geomechanical assessments are mandated by energy regulators to evaluate the caprock integrity and ensure the safe SAGD operations. Commercial reservoir simulation packages started to incorporate geomechanical effects when predicting flow response; however, these geomechanical modules are not able to correctly model the plastic deformations caused by thermal-hydraulic-mechanical (THM) interactions, which has a first order effect on predicting steam chamber propagation and evaluating caprock integrity.
An integrated coupled THM modeling methodology is proposed here to improve the modeling of reservoir deformations and caprock integrity in a heterogeneous oil sand reservoir with interbedded shale barriers. The pressure and temperature front are found to propagate at different speed and that dominate the elastic and plastic deformations caused by changes of shear and mean effective stress. Therefore, four stages are divided in the SAGD process that can be interpretations of changes in stress paths including buildup of pore pressure, generation and dissipation of thermal induced stresses. The response surfaces of minimum factor of safety (FOS) are introduced and computed to provide a conservative estimate for caprock integrity during SAGD of a heterogeneous reservoir with multiple layers of caprocks in Athabasca oil sands.
{"title":"Sequentially Coupled Thermal-Hydraulic-Mechanical Simulation for Geomechanical Assessments of Caprock Integrity in SAGD","authors":"Bo Zhang, Rick Chalaturnyk, Jeff Boisvert","doi":"10.1139/cgj-2023-0228","DOIUrl":"https://doi.org/10.1139/cgj-2023-0228","url":null,"abstract":"Oil sand reservoirs and caprock undergo deformations triggered by pore pressure increases and thermal induced stresses during the steam-assisted-gravity-drainage (SAGD) processes. Geomechanical assessments are mandated by energy regulators to evaluate the caprock integrity and ensure the safe SAGD operations. Commercial reservoir simulation packages started to incorporate geomechanical effects when predicting flow response; however, these geomechanical modules are not able to correctly model the plastic deformations caused by thermal-hydraulic-mechanical (THM) interactions, which has a first order effect on predicting steam chamber propagation and evaluating caprock integrity.
 An integrated coupled THM modeling methodology is proposed here to improve the modeling of reservoir deformations and caprock integrity in a heterogeneous oil sand reservoir with interbedded shale barriers. The pressure and temperature front are found to propagate at different speed and that dominate the elastic and plastic deformations caused by changes of shear and mean effective stress. Therefore, four stages are divided in the SAGD process that can be interpretations of changes in stress paths including buildup of pore pressure, generation and dissipation of thermal induced stresses. The response surfaces of minimum factor of safety (FOS) are introduced and computed to provide a conservative estimate for caprock integrity during SAGD of a heterogeneous reservoir with multiple layers of caprocks in Athabasca oil sands. 
","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136192401","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}
This paper proposes a novel method that addresses a non-traditional class of outlier detection problems. The purpose of most outlier detection methods in the literature is to detect outliers within a dataset. A record can be considered as an outlier if it is distinct from the regular records in the dataset. However, the purpose of the novel outlier detection method proposed by this paper is to detect outlier data groups (a data group may denote a site or a project) with respect to a soil/rock property database. A data group is an outlier group if its characteristics (mean, variance, correlation, or higher order dependency) are distinct from the regular data groups in the database. This paper frames the outlier detection problem into a formal hypothesis testing problem with the null hypothesis “the target data group is identically distributed as the regular groups in the database”. With the hierarchical Bayesian model (HBM) previously developed by the first two authors, the p-value for this hypothesis testing problem can be estimated rigorously. Numerical and real examples show that the p-value can effectively detect outlier data groups as well as outlier records with respect to a database.
{"title":"Detection of outliers with respect to a MUSIC geotechnical database","authors":"Jianye Ching, Kok-Kwang Phoon, Pengsheng Huang","doi":"10.1139/cgj-2023-0188","DOIUrl":"https://doi.org/10.1139/cgj-2023-0188","url":null,"abstract":"This paper proposes a novel method that addresses a non-traditional class of outlier detection problems. The purpose of most outlier detection methods in the literature is to detect outliers within a dataset. A record can be considered as an outlier if it is distinct from the regular records in the dataset. However, the purpose of the novel outlier detection method proposed by this paper is to detect outlier data groups (a data group may denote a site or a project) with respect to a soil/rock property database. A data group is an outlier group if its characteristics (mean, variance, correlation, or higher order dependency) are distinct from the regular data groups in the database. This paper frames the outlier detection problem into a formal hypothesis testing problem with the null hypothesis “the target data group is identically distributed as the regular groups in the database”. With the hierarchical Bayesian model (HBM) previously developed by the first two authors, the p-value for this hypothesis testing problem can be estimated rigorously. Numerical and real examples show that the p-value can effectively detect outlier data groups as well as outlier records with respect to a database.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136108555","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}
Jie Hu, Yunmin Chen, Jing Hang Li, Han Ke, Jun Chao Li, Bin Zhu
Understanding triggering mechanisms of slope failure is of great importance to the stability analysis and safety warning of waste landfill. This paper presents a centrifuge model test on slope failure induced by elevated gas pressure in wet landfill. The formation process of liquid level and gas pressure in the landfill is simulated by means of liquid and gas injections under a centrifugal acceleration of 66.7 g. The pore gas and liquid pressures under two-phase flow condition are monitored separately to clarify the instability process. It is found that the continuous gas injection makes the pore gas pressure increase to peak values of 83.0~100.8 kPa, which are higher than the peak liquid pressures of 61.3~75.6 kPa. The slope failure occurs when the pore gas pressure increases to the peak value and the corresponding shear strength decreases to the critical value. Although the gas injection raises the liquid level, the factor of safety of landfill slope will be overestimated if only considering the effect of liquid pressure. According to the response curves of displacement to gas pressure rise, the critical ratios of gas pressure to earth pressure are determined to be 0.74~0.84, which fall within the range of the prototype landfill. The difference between foam and air on pore pressure distribution is also calculated and discussed.
{"title":"Centrifuge modeling of slope failure induced by elevated gas pressure in wet municipal solid waste landfill","authors":"Jie Hu, Yunmin Chen, Jing Hang Li, Han Ke, Jun Chao Li, Bin Zhu","doi":"10.1139/cgj-2023-0048","DOIUrl":"https://doi.org/10.1139/cgj-2023-0048","url":null,"abstract":"Understanding triggering mechanisms of slope failure is of great importance to the stability analysis and safety warning of waste landfill. This paper presents a centrifuge model test on slope failure induced by elevated gas pressure in wet landfill. The formation process of liquid level and gas pressure in the landfill is simulated by means of liquid and gas injections under a centrifugal acceleration of 66.7 g. The pore gas and liquid pressures under two-phase flow condition are monitored separately to clarify the instability process. It is found that the continuous gas injection makes the pore gas pressure increase to peak values of 83.0~100.8 kPa, which are higher than the peak liquid pressures of 61.3~75.6 kPa. The slope failure occurs when the pore gas pressure increases to the peak value and the corresponding shear strength decreases to the critical value. Although the gas injection raises the liquid level, the factor of safety of landfill slope will be overestimated if only considering the effect of liquid pressure. According to the response curves of displacement to gas pressure rise, the critical ratios of gas pressure to earth pressure are determined to be 0.74~0.84, which fall within the range of the prototype landfill. The difference between foam and air on pore pressure distribution is also calculated and discussed.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"86 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80772540","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}
Yadong Chen, An Deng, Honghua Zhao, Chengzhong Gong, Huasheng Sun, Jiangdong Cai
This study investigated the performance of screw piles under uplift. The screw piles were installed in sand in the laboratory and uplifted to evaluate the effects of the screw thread pitch and relative density of sand on the pile uplift capacity. The uplift capacity was compared with that of the shaft pile using the digital image correlation technique. Discrete element modelling was used to further examine the load-sharing characteristics, axial force, and shaft friction of the screw pile. The results suggest that the screw pile outperformed the shaft pile in terms of uplift capacity, pilesand interactions, and load transfer. The improved uplift performance is attributed to the screw threads reaching out to a larger volume of sand particles to resist the uplift. An equation was also proposed to determine the uplift capacity.
{"title":"Model and numerical analyses of screw pile uplift in dry sand","authors":"Yadong Chen, An Deng, Honghua Zhao, Chengzhong Gong, Huasheng Sun, Jiangdong Cai","doi":"10.1139/cgj-2022-0368","DOIUrl":"https://doi.org/10.1139/cgj-2022-0368","url":null,"abstract":"This study investigated the performance of screw piles under uplift. The screw piles were installed in sand in the laboratory and uplifted to evaluate the effects of the screw thread pitch and relative density of sand on the pile uplift capacity. The uplift capacity was compared with that of the shaft pile using the digital image correlation technique. Discrete element modelling was used to further examine the load-sharing characteristics, axial force, and shaft friction of the screw pile. The results suggest that the screw pile outperformed the shaft pile in terms of uplift capacity, pilesand interactions, and load transfer. The improved uplift performance is attributed to the screw threads reaching out to a larger volume of sand particles to resist the uplift. An equation was also proposed to determine the uplift capacity.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"54 85 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80599881","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 stability of a geogrid-stabilized structure affected by cyclic normal loading (CNL) is significant but has not been fully revealed. Using the discrete element method (DEM), the effect of CNL on the microscale mechanical responses (i.e., stress states, contact evolution, fabric deformation) of the geogrid–aggregate interface direct shear test is first investigated. The complex shear behaviors at the interface with normal cyclic excitation at different frequencies and amplitudes are simulated. The DEM model is able to capture the macroscopic dynamic shear laws at the geogrid–aggregate interface in a similar way to those tested experimentally. The detailed behavior of the aggregate interacting with the geogrid under CNL is investigated. Compared with the simulation under static normal loading (SNL), CNL makes the stabilized layer more prone to failure, which could be quantitively evaluated by analyzing the local shear strain and the interparticle interlocking level. Microscale studies on the load wave propagation process and the confinement zone indicate that the present method can provide an applicable tool for dynamic service assessment and reliable forecasting of the undesirable effect of CNL on a mechanically stabilized layer.
{"title":"Discrete element analysis of geogrid–aggregate interface shear behavior under cyclic normal loading","authors":"Yaqiong Wang, Shijin Feng","doi":"10.1139/cgj-2023-0194","DOIUrl":"https://doi.org/10.1139/cgj-2023-0194","url":null,"abstract":"The stability of a geogrid-stabilized structure affected by cyclic normal loading (CNL) is significant but has not been fully revealed. Using the discrete element method (DEM), the effect of CNL on the microscale mechanical responses (i.e., stress states, contact evolution, fabric deformation) of the geogrid–aggregate interface direct shear test is first investigated. The complex shear behaviors at the interface with normal cyclic excitation at different frequencies and amplitudes are simulated. The DEM model is able to capture the macroscopic dynamic shear laws at the geogrid–aggregate interface in a similar way to those tested experimentally. The detailed behavior of the aggregate interacting with the geogrid under CNL is investigated. Compared with the simulation under static normal loading (SNL), CNL makes the stabilized layer more prone to failure, which could be quantitively evaluated by analyzing the local shear strain and the interparticle interlocking level. Microscale studies on the load wave propagation process and the confinement zone indicate that the present method can provide an applicable tool for dynamic service assessment and reliable forecasting of the undesirable effect of CNL on a mechanically stabilized layer.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"21 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81759207","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}
A custom-designed apparatus (referred to as the Ageing Column) is used to age a 4.8-mm thick elastomeric bituminous geomembrane (BGM) under single-sided exposure to a synthetic municipal solid waste (MSW) leachate and a synthetic high pH mining solution (pH 11.5) at 55, 70, and 85°C. This apparatus involves a closer simulation of the BGM’s chemical exposure conditions in the field than the double-sided immersion tests in which the BGM is exposed to the solution from both surfaces. The mechanical, rheological, and chemical properties of the BGM are examined to assess the degradation in the BGM components relative to double-sided immersion experiments. While the single-sided ageing of the BGM reduces the degradation rates in the BGM mechanical properties, it does not affect the degradation rate of the bitumen coat relative to the double-sided exposure. Additionally, the exposure of the BGM to the MSW leachate resulted in faster degradation in its mechanical properties but slower degradation in the bitumen coat than that obtained in the exposure to the mining solution. However, predictions of the time to nominal failure of the BGM established using Arrhenius modelling at different temperatures show that the temperature effect is more significant on the BGM durability than the chemistry of the considered solutions.
{"title":"The long-term performance of a bituminous geomembrane (BGM) under single-sided exposure conditions","authors":"F. Abdelaal, A. Samea","doi":"10.1139/cgj-2023-0180","DOIUrl":"https://doi.org/10.1139/cgj-2023-0180","url":null,"abstract":"A custom-designed apparatus (referred to as the Ageing Column) is used to age a 4.8-mm thick elastomeric bituminous geomembrane (BGM) under single-sided exposure to a synthetic municipal solid waste (MSW) leachate and a synthetic high pH mining solution (pH 11.5) at 55, 70, and 85°C. This apparatus involves a closer simulation of the BGM’s chemical exposure conditions in the field than the double-sided immersion tests in which the BGM is exposed to the solution from both surfaces. The mechanical, rheological, and chemical properties of the BGM are examined to assess the degradation in the BGM components relative to double-sided immersion experiments. While the single-sided ageing of the BGM reduces the degradation rates in the BGM mechanical properties, it does not affect the degradation rate of the bitumen coat relative to the double-sided exposure. Additionally, the exposure of the BGM to the MSW leachate resulted in faster degradation in its mechanical properties but slower degradation in the bitumen coat than that obtained in the exposure to the mining solution. However, predictions of the time to nominal failure of the BGM established using Arrhenius modelling at different temperatures show that the temperature effect is more significant on the BGM durability than the chemistry of the considered solutions.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"23 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89232083","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 paper develops an analytical model based on the stress equilibrium for the design of steep slope geosynthetic liner systems to overcome downdrag loads from waste settlement. This analytical model calculates the required tensile stiffness for a high strength/stiffness geotextile (HS-GTX) reinforcement over the GMB to limit the maximum HS-GTX tensile strain to 5% and the maximum GMB strain to 4% on the side slope. The numerical model illustrates the need for reducing the GMB tensile strains for a single GMB liner on a steep landfill slope and confirms that the use of a HS-GTX over the GMB is able to limit the maximum HS-GTX and GMB tensile strains to the acceptable strain levels. The analytical model developed in this paper is a practical tool for preliminary design to limit tensile strains of the HS-GTX and GMB in a steep slope geosynthetic liner system.
{"title":"Analytical and Numerical Models for Strain and Load Calculations for Geosynthetic Liner Systems on Steep Slopes","authors":"Yan Yu, R. K. Rowe","doi":"10.1139/cgj-2023-0123","DOIUrl":"https://doi.org/10.1139/cgj-2023-0123","url":null,"abstract":"The paper develops an analytical model based on the stress equilibrium for the design of steep slope geosynthetic liner systems to overcome downdrag loads from waste settlement. This analytical model calculates the required tensile stiffness for a high strength/stiffness geotextile (HS-GTX) reinforcement over the GMB to limit the maximum HS-GTX tensile strain to 5% and the maximum GMB strain to 4% on the side slope. The numerical model illustrates the need for reducing the GMB tensile strains for a single GMB liner on a steep landfill slope and confirms that the use of a HS-GTX over the GMB is able to limit the maximum HS-GTX and GMB tensile strains to the acceptable strain levels. The analytical model developed in this paper is a practical tool for preliminary design to limit tensile strains of the HS-GTX and GMB in a steep slope geosynthetic liner system.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"85 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90798023","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}
Hu Lu, Jiangwei Shi, Chao Shi, Weiwei Pei, Shaoming Chen
This study conducted both three-dimensional physical model tests and numerical back-analyses to examine the performance of a single pile subjected to twin tunnelling beneath the pile toe in dry sand. Moreover, numerical parametric analyses were carried out to assess the impact of working load level and tunnel volume loss on pile behaviour. The findings revealed that the first tunnelling induced a 1.9%dp (pile diameter) settlement in the pile when the pile toe was 0.5D (tunnel diameter) above the twin tunnels, which had a 1.0% volume loss. The settlement was accompanied by an upward load transfer mechanism. The second tunnelling had a reduced impact and induced only 76% of the settlement caused by the first tunnelling. The study also showed that tunnelling-induced shearing behaviours weakened beneath the pile toe with a decrease in working load, resulting in reduced pile head settlement. Moreover, the computed pile settlement increased by 178% when the tunnel volume loss increased from 0.5% to 2%. The findings of this study offer valuable data for the validation and calibration of numerical models. In addition, the outcome from this study provides useful insights into the prediction of the pile-soil-tunnel interaction when subjected to twin tunnelling.
{"title":"Assessment of Twin Tunnelling Induced Settlement and Load Transfer Mechanism of a Single Pile in Dry Sand","authors":"Hu Lu, Jiangwei Shi, Chao Shi, Weiwei Pei, Shaoming Chen","doi":"10.1139/cgj-2023-0196","DOIUrl":"https://doi.org/10.1139/cgj-2023-0196","url":null,"abstract":"This study conducted both three-dimensional physical model tests and numerical back-analyses to examine the performance of a single pile subjected to twin tunnelling beneath the pile toe in dry sand. Moreover, numerical parametric analyses were carried out to assess the impact of working load level and tunnel volume loss on pile behaviour. The findings revealed that the first tunnelling induced a 1.9%dp (pile diameter) settlement in the pile when the pile toe was 0.5D (tunnel diameter) above the twin tunnels, which had a 1.0% volume loss. The settlement was accompanied by an upward load transfer mechanism. The second tunnelling had a reduced impact and induced only 76% of the settlement caused by the first tunnelling. The study also showed that tunnelling-induced shearing behaviours weakened beneath the pile toe with a decrease in working load, resulting in reduced pile head settlement. Moreover, the computed pile settlement increased by 178% when the tunnel volume loss increased from 0.5% to 2%. The findings of this study offer valuable data for the validation and calibration of numerical models. In addition, the outcome from this study provides useful insights into the prediction of the pile-soil-tunnel interaction when subjected to twin tunnelling.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"26 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79271023","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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