Applications of Bayesian updating commonly treat soil parameters as random variables. A significant issue with this is that soil parameters are highly subjective. Therefore, using traditional parameter-based models, Bayesian analysis starts from a subjective prior and it is unclear how this may influence the overall results of a study. In this paper, Bayesian updating is combined with a data-driven method, known as CRACA (i.e. CReep And Consolidation Analysis), for predicting the settlement of embankments on soft soil. Importantly, the method directly ingests measured oedometer data and therefore avoids the subjectivity involved in parameter selection. Because parameters are not used, scaling factors are introduced that account uncertainty associated with the laboratory measurements and the automated interpretation process. These factors have an initial value of unity (returning the prior) and are updated in a Bayesian framework as settlement monitoring data is revealed over time to improve future forecasts. The model was applied to an embankment case history and was shown to result in a rapid improvement in the accuracy and a narrowing of the 95% confidence interval as settlement monitoring data is revealed to the model.
{"title":"From data to decision: combining Bayesian updating with a data-driven prior to forecast the settlement of embankments on soft soils","authors":"Xiao Wan, J. Doherty","doi":"10.1139/cgj-2023-0075","DOIUrl":"https://doi.org/10.1139/cgj-2023-0075","url":null,"abstract":"Applications of Bayesian updating commonly treat soil parameters as random variables. A significant issue with this is that soil parameters are highly subjective. Therefore, using traditional parameter-based models, Bayesian analysis starts from a subjective prior and it is unclear how this may influence the overall results of a study. In this paper, Bayesian updating is combined with a data-driven method, known as CRACA (i.e. CReep And Consolidation Analysis), for predicting the settlement of embankments on soft soil. Importantly, the method directly ingests measured oedometer data and therefore avoids the subjectivity involved in parameter selection. Because parameters are not used, scaling factors are introduced that account uncertainty associated with the laboratory measurements and the automated interpretation process. These factors have an initial value of unity (returning the prior) and are updated in a Bayesian framework as settlement monitoring data is revealed over time to improve future forecasts. The model was applied to an embankment case history and was shown to result in a rapid improvement in the accuracy and a narrowing of the 95% confidence interval as settlement monitoring data is revealed to the model.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"39 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79290025","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 presents the results of field tests performed to investigate the installation effects of pre-bored grouted planted (PGP) pile in deep clayey soil. The test results show that the drilling and grouting process induced large horizontal soil displacements in the soil within a radial distance of 2 d (d is pile diameter), and the maximum horizontal soil displacements induced by the drilling and grouting process were smaller than 15.9 mm when the radial distance reached 4 – 5 d. Moreover, the horizontal soil displacements decreased along the soil layer depth, as the superficial soil layers were of small deformation modulus and lateral soil pressure. The drilling process brought large excess pore water pressures in the soil when the radial distance was less than 3 d, and the excess pore water pressures induced by the drilling stage were all less than 55 kPa when the radial distance was in the range 4 – 6 d. The drilling process also induced some lateral soil pressure increases in the soil within a radial distance of 3 d, while the measured maximum lateral soil pressure increases were smaller than 10.9 kPa when the radial distance increased to 4 d.
{"title":"Field study on installation effects of pre-bored grouted planted pile in deep clayey soil","authors":"Jia-jin Zhou, Jian-lin Yu, X. Gong, Ri-hong Zhang","doi":"10.1139/cgj-2022-0530","DOIUrl":"https://doi.org/10.1139/cgj-2022-0530","url":null,"abstract":"This paper presents the results of field tests performed to investigate the installation effects of pre-bored grouted planted (PGP) pile in deep clayey soil. The test results show that the drilling and grouting process induced large horizontal soil displacements in the soil within a radial distance of 2 d (d is pile diameter), and the maximum horizontal soil displacements induced by the drilling and grouting process were smaller than 15.9 mm when the radial distance reached 4 – 5 d. Moreover, the horizontal soil displacements decreased along the soil layer depth, as the superficial soil layers were of small deformation modulus and lateral soil pressure. The drilling process brought large excess pore water pressures in the soil when the radial distance was less than 3 d, and the excess pore water pressures induced by the drilling stage were all less than 55 kPa when the radial distance was in the range 4 – 6 d. The drilling process also induced some lateral soil pressure increases in the soil within a radial distance of 3 d, while the measured maximum lateral soil pressure increases were smaller than 10.9 kPa when the radial distance increased to 4 d.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"233 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89033691","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 retention behavior of the loess-paleosol sequence has important significance for hydrology and paleoclimate. This report examines the soil-water retention curves and microstructures of the Luochuan loess-paleosol sequence. The experimental results demonstrated that as burial depth increases, there is a significant change in the soil-water retention curve of loess-paleosol sequence. Simultaneously, the saturated volumetric water content and water loss rate gradually decrease, while the air entry value and residual water content increase. As a whole, the loess layer has a lower water-holding capacity than the adjacent paleosol layer. Accordingly, the microstructure of the loess-paleosol sequence changes considerably with the burial depth. The microstructure changes from overhead structure to matrix structure. The results suggest that the loess layer deposited in cold and dry climate conditions can act as an aquifer, which is related to weak pedogenic weathering. In contrast, paleosol layers that were formed in warm, humid climates underwent significant pedogenic weathering and can behave as an aquiclude. Based on the previously mentioned results, the link between paleoclimate changes and the current hydrological system has been explored.
{"title":"Soil-water retention behavior of a loess-paleosol sequence and its significance for hydrology and paleoclimate: A case study from the Luochuan profile of the Loess Plateau, China","authors":"Hai-man Wang, W. Ni","doi":"10.1139/cgj-2023-0144","DOIUrl":"https://doi.org/10.1139/cgj-2023-0144","url":null,"abstract":"The soil water retention behavior of the loess-paleosol sequence has important significance for hydrology and paleoclimate. This report examines the soil-water retention curves and microstructures of the Luochuan loess-paleosol sequence. The experimental results demonstrated that as burial depth increases, there is a significant change in the soil-water retention curve of loess-paleosol sequence. Simultaneously, the saturated volumetric water content and water loss rate gradually decrease, while the air entry value and residual water content increase. As a whole, the loess layer has a lower water-holding capacity than the adjacent paleosol layer. Accordingly, the microstructure of the loess-paleosol sequence changes considerably with the burial depth. The microstructure changes from overhead structure to matrix structure. The results suggest that the loess layer deposited in cold and dry climate conditions can act as an aquifer, which is related to weak pedogenic weathering. In contrast, paleosol layers that were formed in warm, humid climates underwent significant pedogenic weathering and can behave as an aquiclude. Based on the previously mentioned results, the link between paleoclimate changes and the current hydrological system has been explored.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"6 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81947657","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}
H. Bernardes, Renato Pinto da Cunha, Aleones José da Cruz Junior, M. Sales, Juan Félix Rodríguez Rebolledo
This paper aims to analyze and describe the geotechnical behavior of a piled raft foundation of a tall building (53 floors, 172.4 m high) through the monitoring of strains in the building’s columns and piles, the stresses at the raft-soil interface, and the foundation settlements. Field and laboratory tests were performed, and associated with axisymmetric and three-dimensional finite element analysis to the assessment of the measured data. The monitoring of the pile strains suggests the occurrence of soil expansion, caused by the raft excavation process, up to approximately six months after the excavation was completed. The presence of different soil profiles under the raft, with different mechanical properties, affected the distribution of the foundation settlements and the pile loads. Initially, the average pile loads were concentrated in the perimeter elements, but, as the construction of the building evolved, they tended to become more uniform. The effect of the superstructure stiffness caused successive load redistributions in the columns, which contributed to the maintenance of the maximum angular distortion of the building within the allowable values and reduced the load difference between the piles positioned in opposite soil profiles.
{"title":"Analysis of the Geotechnical Behavior of a Piled Raft in Tropical Lateritic Soil Based on Long-Term Monitoring of Columns, Piles, and Raft-Soil Interface","authors":"H. Bernardes, Renato Pinto da Cunha, Aleones José da Cruz Junior, M. Sales, Juan Félix Rodríguez Rebolledo","doi":"10.1139/cgj-2022-0675","DOIUrl":"https://doi.org/10.1139/cgj-2022-0675","url":null,"abstract":"This paper aims to analyze and describe the geotechnical behavior of a piled raft foundation of a tall building (53 floors, 172.4 m high) through the monitoring of strains in the building’s columns and piles, the stresses at the raft-soil interface, and the foundation settlements. Field and laboratory tests were performed, and associated with axisymmetric and three-dimensional finite element analysis to the assessment of the measured data. The monitoring of the pile strains suggests the occurrence of soil expansion, caused by the raft excavation process, up to approximately six months after the excavation was completed. The presence of different soil profiles under the raft, with different mechanical properties, affected the distribution of the foundation settlements and the pile loads. Initially, the average pile loads were concentrated in the perimeter elements, but, as the construction of the building evolved, they tended to become more uniform. The effect of the superstructure stiffness caused successive load redistributions in the columns, which contributed to the maintenance of the maximum angular distortion of the building within the allowable values and reduced the load difference between the piles positioned in opposite soil profiles.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"19 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76387789","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}
ABSTRACT Common practice for determining the required ice thickness for vehicles and equipment relies on Gold’s Formula as outlined in Provincial and Territorial publications relating to ice safety [e.g. 1-4]. This practice persists despite recent advances in ice engineering knowledge that provide more comprehensive design methods utilizing limit states design approaches (Masterson 2009, Kerr, 1996). The authors have identified that the use of Gold’s Formula for determining required ice thickness may lead to unsafe practices when utilized in the context of heavy construction equipment, increasing the risk of ice breakthrough to personnel and equipment. The authors use recent design examples to demonstrate instances in which the use of Gold’s Formula results in predicted flexural tensile stresses in the ice cover that exceed the maximum design stress recommended in contemporary literature (Masterson 2009, Hayley and Proskin 2008, US Army Corps of Engineers 2002, Gold 1981). In the case of large excavators (53 metric tonnes), and heavy dozers (40 metric tonnes), as examples, the use of Gold’s Formula for determining the required ice thickness will result in predicted flexural tensile stresses that exceed the recommended maximum design stress by 56%-71%.
{"title":"LIMITIATIONS OF GOLD’S FORMULA FOR PREDICTING ICE THICKNESS REQUIREMENTS FOR HEAVY EQUIPMENT","authors":"Alan Fitzgerald, Willem Janse van Rensburg","doi":"10.1139/cgj-2022-0464","DOIUrl":"https://doi.org/10.1139/cgj-2022-0464","url":null,"abstract":"ABSTRACT Common practice for determining the required ice thickness for vehicles and equipment relies on Gold’s Formula as outlined in Provincial and Territorial publications relating to ice safety [e.g. 1-4]. This practice persists despite recent advances in ice engineering knowledge that provide more comprehensive design methods utilizing limit states design approaches (Masterson 2009, Kerr, 1996). The authors have identified that the use of Gold’s Formula for determining required ice thickness may lead to unsafe practices when utilized in the context of heavy construction equipment, increasing the risk of ice breakthrough to personnel and equipment. The authors use recent design examples to demonstrate instances in which the use of Gold’s Formula results in predicted flexural tensile stresses in the ice cover that exceed the maximum design stress recommended in contemporary literature (Masterson 2009, Hayley and Proskin 2008, US Army Corps of Engineers 2002, Gold 1981). In the case of large excavators (53 metric tonnes), and heavy dozers (40 metric tonnes), as examples, the use of Gold’s Formula for determining the required ice thickness will result in predicted flexural tensile stresses that exceed the recommended maximum design stress by 56%-71%.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"8 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89615714","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Field observed shrinkage was quantified and compared for one GCL type left covered only by a black geomembrane, a white geomembrane and 0.3 m of gravel cover, and additionally for four GCLs left covered only by a black geomembrane for up to 28 months exposure at the QUELTS II experiment. All GCLs were needle-punched geotextile encased: one containing fine granular bentonite, two with powdered bentonite, one with polymer amended granular bentonite, and one multicomponent GCL with a film coating installed film up. All the GCLs examined have the potential to shrink with the magnitude of the shrinkage primarily dependent on the thermal/moisture cycles to which it is subjected and the degree of adhesion between panel overlaps. It is shown that the panel overlap adhesion can be highly variable and this is primarily attributed to condensation of water vapour below geomembrane wrinkles during daily thermal cycles. With a an initial GCL overlap of 300 mm, the shrinkage observed over 28 months left ≥ 32% of the original overlap, however if the overlap had been only 150 mm then gaps or ineffective seems would have occurred for several GCLs. Guidance regarding mitigating GCL panel shrinkage is provided.
{"title":"Field observed GCL panel shrinkage for five GCLs in composite liners","authors":"Amy K. Rentz, R. Brachman, R. Rowe, W. A. Take","doi":"10.1139/cgj-2022-0397","DOIUrl":"https://doi.org/10.1139/cgj-2022-0397","url":null,"abstract":"Field observed shrinkage was quantified and compared for one GCL type left covered only by a black geomembrane, a white geomembrane and 0.3 m of gravel cover, and additionally for four GCLs left covered only by a black geomembrane for up to 28 months exposure at the QUELTS II experiment. All GCLs were needle-punched geotextile encased: one containing fine granular bentonite, two with powdered bentonite, one with polymer amended granular bentonite, and one multicomponent GCL with a film coating installed film up. All the GCLs examined have the potential to shrink with the magnitude of the shrinkage primarily dependent on the thermal/moisture cycles to which it is subjected and the degree of adhesion between panel overlaps. It is shown that the panel overlap adhesion can be highly variable and this is primarily attributed to condensation of water vapour below geomembrane wrinkles during daily thermal cycles. With a an initial GCL overlap of 300 mm, the shrinkage observed over 28 months left ≥ 32% of the original overlap, however if the overlap had been only 150 mm then gaps or ineffective seems would have occurred for several GCLs. Guidance regarding mitigating GCL panel shrinkage is provided.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"63 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77219182","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}
Jun-ping Ren, Xudong Fan, Xiong Yu, Sai Vanapalli, Shoulong Zhang
The variation of unfrozen water content (UWC) has a significant influence on the physical and mechanical behaviors of frozen soils. Several empirical, semi-empirical, physical, and theoretical models are available in the literature to estimate the UWC in frozen soils. However, these models have limitations due to the complex interactions of various influencing factors that are not well understood or fully established. For this reason, in the present study, an artificial neural network (ANN) modeling framework is proposed and the PyTorch package is used for predicting UWC. Extensive UWC data of various types of soils tested under various conditions were collected through an extensive search of the literature. The developed ANN model showed good performance for the testing dataset. Its performance was further compared with two traditional statistical models on four soils and found to outperform these traditional models. Detailed discussions on the developed ANN model, and its strengths and limitations in comparison to different other models are provided. The study demonstrates that the proposed ANN model is simple yet reliable for estimating the UWC of various soils. In addition, the summarized UWC data and the proposed machine learning modeling framework are valuable for future studies related to frozen soils.
{"title":"Use of an artificial neural network model for estimation of unfrozen water content in frozen soils","authors":"Jun-ping Ren, Xudong Fan, Xiong Yu, Sai Vanapalli, Shoulong Zhang","doi":"10.1139/cgj-2022-0035","DOIUrl":"https://doi.org/10.1139/cgj-2022-0035","url":null,"abstract":"The variation of unfrozen water content (UWC) has a significant influence on the physical and mechanical behaviors of frozen soils. Several empirical, semi-empirical, physical, and theoretical models are available in the literature to estimate the UWC in frozen soils. However, these models have limitations due to the complex interactions of various influencing factors that are not well understood or fully established. For this reason, in the present study, an artificial neural network (ANN) modeling framework is proposed and the PyTorch package is used for predicting UWC. Extensive UWC data of various types of soils tested under various conditions were collected through an extensive search of the literature. The developed ANN model showed good performance for the testing dataset. Its performance was further compared with two traditional statistical models on four soils and found to outperform these traditional models. Detailed discussions on the developed ANN model, and its strengths and limitations in comparison to different other models are provided. The study demonstrates that the proposed ANN model is simple yet reliable for estimating the UWC of various soils. In addition, the summarized UWC data and the proposed machine learning modeling framework are valuable for future studies related to frozen soils.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134984308","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}
Simon Oberhollenzer, L. Hauser, Martin Ehall, R. Marte, F. Tschuchnigg, H. Schweiger
The compaction control of earth works is an essential task in geotechnical engineering. In order to build more sustainably and to reduce project costs, fine-grained materials are more often used for embankment construction nowadays. The quality control of compacted soil layers is usually defined in terms of deformation moduli obtained from static and dynamic plate load tests or based on the degree of compaction, which is generally related to the Proctor density. Penetration tests, such as cone penetration tests (CPT), seismic flat dilatometer tests (SDMT) or dynamic probings (DPM), show a potential for assessing the compaction along vertical profiles but no standardized quality criteria have been elaborated yet. The present work investigates the effects of different water contents and degrees of soil stabilization on results of CPT, SDMT, DPM, plate load tests and Proctor tests for an 8 m high trial embankment, characterized by a clayey to silty material. CPT and DMT results were found to strongly correlate with deformation moduli of static and dynamic plate load tests, enabling the definition of new quality criteria for compaction control.
{"title":"Quality control of fine-grained embankments using penetration tests","authors":"Simon Oberhollenzer, L. Hauser, Martin Ehall, R. Marte, F. Tschuchnigg, H. Schweiger","doi":"10.1139/cgj-2022-0055","DOIUrl":"https://doi.org/10.1139/cgj-2022-0055","url":null,"abstract":"The compaction control of earth works is an essential task in geotechnical engineering. In order to build more sustainably and to reduce project costs, fine-grained materials are more often used for embankment construction nowadays. The quality control of compacted soil layers is usually defined in terms of deformation moduli obtained from static and dynamic plate load tests or based on the degree of compaction, which is generally related to the Proctor density. Penetration tests, such as cone penetration tests (CPT), seismic flat dilatometer tests (SDMT) or dynamic probings (DPM), show a potential for assessing the compaction along vertical profiles but no standardized quality criteria have been elaborated yet. The present work investigates the effects of different water contents and degrees of soil stabilization on results of CPT, SDMT, DPM, plate load tests and Proctor tests for an 8 m high trial embankment, characterized by a clayey to silty material. CPT and DMT results were found to strongly correlate with deformation moduli of static and dynamic plate load tests, enabling the definition of new quality criteria for compaction control.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"289 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79418778","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 strength and stiffness of a composite rockmass (intact material, defects, joints, bedding, etc.) are primary inputs for the engineering analysis of rock slopes and underground excavations. The Geological Strength Index (GSI) has served rock engineering for three decades as a rockmass assessment system based on the blockiness of the rockmass and discontinuity condition. GSI is used to factor the Hoek-Brown strength envelope for intact rock to represent jointed rockmasses in conventional equivalent-continuum numerical modelling. Modern numerical tools can represent networks of discrete (explicit) structure with assigned discontinuity properties. This provides an opportunity to compare explicit structural modelling with the conventional implicit equivalent-continuum approach. In this paper, explicit structural models are developed using elasto-plastic (constant-strength) constitutive models for intact rock and realistic parametric ranges for explicit structure properties. Explicit model results are compared to equivalent-continuum results, validating the classical implicit approach while also identifying key limitations. Explicit models with post-yield weakening of the intact and structural elements are then developed and compared to post-yield weakening implicit models that use post-yield dilation and empirical relationships between peak and residual GSI. The results provide guidance for practical modelling in strain-weakening rockmasses, including recommendations for post-yield dilation in the traditional implicit approach.
{"title":"Elasto-Plastic and Post-Yield Weakening Jointed Rockmass Response in a Comparison of Equivalent-Continuum and Explicit Structural Models","authors":"C. P. Fischer, M. Diederichs","doi":"10.1139/cgj-2022-0190","DOIUrl":"https://doi.org/10.1139/cgj-2022-0190","url":null,"abstract":"The strength and stiffness of a composite rockmass (intact material, defects, joints, bedding, etc.) are primary inputs for the engineering analysis of rock slopes and underground excavations. The Geological Strength Index (GSI) has served rock engineering for three decades as a rockmass assessment system based on the blockiness of the rockmass and discontinuity condition. GSI is used to factor the Hoek-Brown strength envelope for intact rock to represent jointed rockmasses in conventional equivalent-continuum numerical modelling. Modern numerical tools can represent networks of discrete (explicit) structure with assigned discontinuity properties. This provides an opportunity to compare explicit structural modelling with the conventional implicit equivalent-continuum approach. In this paper, explicit structural models are developed using elasto-plastic (constant-strength) constitutive models for intact rock and realistic parametric ranges for explicit structure properties. Explicit model results are compared to equivalent-continuum results, validating the classical implicit approach while also identifying key limitations. Explicit models with post-yield weakening of the intact and structural elements are then developed and compared to post-yield weakening implicit models that use post-yield dilation and empirical relationships between peak and residual GSI. The results provide guidance for practical modelling in strain-weakening rockmasses, including recommendations for post-yield dilation in the traditional implicit approach.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"16 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79711751","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}
Recycled concrete aggregate (RCA) can be used in landfill and slope cover systems, where its unsaturated hydraulic properties play an important role. The hydraulic behavior of RCAs can be potentially controlled through mixing coarse and fine aggregates by a pre-determined proportion, which lacks experimental validation. In this study, water retention curve (WRC) and permeability function (PF) of RCAs with different fine aggregate contents (fc) were investigated. Experiments on 9 RCAs with different gradations reveal that when fc is between 20% and 30%, a second air entry value appears, and the shape of both WRC and PF becomes bimodal, which is probably resulted from an uneven dual-peak pore-size distribution. With an increasing fc, the first air entry value and the residual water content increases. The unsaturated coefficient of permeability decreases with the increasing fc for a low suction level (< 0.1 kPa), but increases with the raise of fc for high suction (> 10 kPa). Overall, adopting a properly mixed RCA with fc value of less than 10% or over 40%, instead of a narrowly-graded RCA, is recommended for coarse- and fine-grained layers in a capillary barrier, respectively.
{"title":"Effects of fine aggregate content on the unsaturated hydraulic characteristics of recycled concrete aggregate","authors":"Rui Chen, Fan Wu, C. Ng, P. Tai, Dong-jie Mei","doi":"10.1139/cgj-2022-0380","DOIUrl":"https://doi.org/10.1139/cgj-2022-0380","url":null,"abstract":"Recycled concrete aggregate (RCA) can be used in landfill and slope cover systems, where its unsaturated hydraulic properties play an important role. The hydraulic behavior of RCAs can be potentially controlled through mixing coarse and fine aggregates by a pre-determined proportion, which lacks experimental validation. In this study, water retention curve (WRC) and permeability function (PF) of RCAs with different fine aggregate contents (fc) were investigated. Experiments on 9 RCAs with different gradations reveal that when fc is between 20% and 30%, a second air entry value appears, and the shape of both WRC and PF becomes bimodal, which is probably resulted from an uneven dual-peak pore-size distribution. With an increasing fc, the first air entry value and the residual water content increases. The unsaturated coefficient of permeability decreases with the increasing fc for a low suction level (< 0.1 kPa), but increases with the raise of fc for high suction (> 10 kPa). Overall, adopting a properly mixed RCA with fc value of less than 10% or over 40%, instead of a narrowly-graded RCA, is recommended for coarse- and fine-grained layers in a capillary barrier, respectively.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"32 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79933490","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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