Yufei Wang, C. O’Loughlin, Zefeng Zhou, Christophe Gaudin
The undrained shear strength of fine-grained soils changes with time, reducing due to pore pressure generation, and increasing during consolidation. There is an increasing appetite to recognise these temporal soil strength changes in offshore geotechnical design, as it provides a basis for potentially less conservative designs. Contributions to this endeavour are reported across two companion papers. This first paper extends an existing effective stress framework that relates generation of pore pressure to accumulated plastic shear strain, allowing undrained shear strength to be calculated within the context of critical-state soil mechanics. The main development is the extension of the computational domain to two dimensions, allowing calculations to be made for boundary value problems that cannot be satisfactorily simplified to 1D conditions. The magnitude and distribution of accumulated shear strain surrounding objects buried in soil are quantified through a series of large deformation finite element analyses. These spatial distributions are described using a strain influence function in the new 2D framework to calculate the extent and magnitude of excess pore pressure, and in turn the mobilised soil strength around the buried object. The performance of the 2D framework is examined in the companion paper through retrospective simulations of experimental and numerical data.
{"title":"A two-dimensional effective stress framework for modelling whole-life soil strength changes due to pore pressure generation and dissipation, Part 1: Formulation","authors":"Yufei Wang, C. O’Loughlin, Zefeng Zhou, Christophe Gaudin","doi":"10.1139/cgj-2022-0331","DOIUrl":"https://doi.org/10.1139/cgj-2022-0331","url":null,"abstract":"The undrained shear strength of fine-grained soils changes with time, reducing due to pore pressure generation, and increasing during consolidation. There is an increasing appetite to recognise these temporal soil strength changes in offshore geotechnical design, as it provides a basis for potentially less conservative designs. Contributions to this endeavour are reported across two companion papers. This first paper extends an existing effective stress framework that relates generation of pore pressure to accumulated plastic shear strain, allowing undrained shear strength to be calculated within the context of critical-state soil mechanics. The main development is the extension of the computational domain to two dimensions, allowing calculations to be made for boundary value problems that cannot be satisfactorily simplified to 1D conditions. The magnitude and distribution of accumulated shear strain surrounding objects buried in soil are quantified through a series of large deformation finite element analyses. These spatial distributions are described using a strain influence function in the new 2D framework to calculate the extent and magnitude of excess pore pressure, and in turn the mobilised soil strength around the buried object. The performance of the 2D framework is examined in the companion paper through retrospective simulations of experimental and numerical data.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2023-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139212276","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}
Upon dynamic loading, saturated soil loses its strength and behaves differently with respect to the excess pore pressure variation resulting in volumetric-induced settlements. Traditionally, these settlements have been evaluated using standard charts based on one soil type and its relative density (RD). To assess these settlements, this study established a unique experimental methodology based on two laboratory tests: triaxial simple shear and piezoelectric ring actuator technique. Fifty-seven tests were performed on Ottawa F65 sand under strain-controlled cyclic and post-cyclic conditions. A chart was generated, revealing a relationship between the dissipated energy from cyclic loading and volumetric strain (v), based on the shear wave velocity as a controlling factor. This study was compared with previous studies to verify the compatibility of the proposed approach. Another novelty was revealed by studying v variation with the dissipated pressure. This variation is presented in a post-seismic chart, in which deformations are tracked based on the initial soil state and maximum excess pore pressure generation ratio (Rumax). For each RD, the soil is divided between liquefied and non-liquefied states according to a specific Rumax (Rumax-trigger point). The calculation of the volume compressibility coefficient is proven to serve as a liquefaction-triggering criterion identifying the liquefied state.
{"title":"Experimental Approach for Assessing Dissipated Excess Pore Pressure Induced Settlement","authors":"A. Bayoumi, M. Chekired, M. Karray","doi":"10.1139/cgj-2022-0063","DOIUrl":"https://doi.org/10.1139/cgj-2022-0063","url":null,"abstract":"Upon dynamic loading, saturated soil loses its strength and behaves differently with respect to the excess pore pressure variation resulting in volumetric-induced settlements. Traditionally, these settlements have been evaluated using standard charts based on one soil type and its relative density (RD). To assess these settlements, this study established a unique experimental methodology based on two laboratory tests: triaxial simple shear and piezoelectric ring actuator technique. Fifty-seven tests were performed on Ottawa F65 sand under strain-controlled cyclic and post-cyclic conditions. A chart was generated, revealing a relationship between the dissipated energy from cyclic loading and volumetric strain (v), based on the shear wave velocity as a controlling factor. This study was compared with previous studies to verify the compatibility of the proposed approach. Another novelty was revealed by studying v variation with the dissipated pressure. This variation is presented in a post-seismic chart, in which deformations are tracked based on the initial soil state and maximum excess pore pressure generation ratio (Rumax). For each RD, the soil is divided between liquefied and non-liquefied states according to a specific Rumax (Rumax-trigger point). The calculation of the volume compressibility coefficient is proven to serve as a liquefaction-triggering criterion identifying the liquefied state.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2023-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139212016","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}
Rigid-wall permeameter testing of two potentially unstable gradations established the critical hydraulic gradient to trigger instability is smaller for upward flow than for downward flow. The experimental finding is explained with reference to the Skempton-Brogan stress reduction factor α in the finer fraction content of the soil. Theory uses the α-factor to define a hydro-mechanical envelope in gradient-stress space that is independent of flow direction, and the experimental results are found in good agreement with the theory. Testing with upward flow is recommended to determine the value of α for an internally unstable gradation because, in contrast to downward flow, there is no requirement for an outflow boundary.
{"title":"Internal Instability of Cohesionless Soils in Upward and Downward Flow: An Experimental Verification of Theory","authors":"Maoxin Li, R. Fannin, Mark Foster, Li Yan","doi":"10.1139/cgj-2023-0011","DOIUrl":"https://doi.org/10.1139/cgj-2023-0011","url":null,"abstract":"Rigid-wall permeameter testing of two potentially unstable gradations established the critical hydraulic gradient to trigger instability is smaller for upward flow than for downward flow. The experimental finding is explained with reference to the Skempton-Brogan stress reduction factor α in the finer fraction content of the soil. Theory uses the α-factor to define a hydro-mechanical envelope in gradient-stress space that is independent of flow direction, and the experimental results are found in good agreement with the theory. Testing with upward flow is recommended to determine the value of α for an internally unstable gradation because, in contrast to downward flow, there is no requirement for an outflow boundary.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2023-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139211791","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 study characterises the effects of naturally varying organic content on the compression and shear behaviour of a marine silty-clay from the Netherlands. Index properties and mechanical properties are determined through laboratory tests, including oedometer and multistage loading-unloading triaxial stress paths. The results indicate a significant impact of the organic content on the compression response, with both the loading and reloading indexes increasing as the loss on ignition increases from 3% to 7%. Additionally, the study suggests a directional response of the compression behaviour, with the loading index increasing with the stress ratio. The influence of the organic content on shear strength appears to be less significant. No brittle response is observed during shearing and a similar ultimate stress ratio is attained by all samples. However, a unique critical state line can only be identified for samples with similar organic content, as its intercept and slope are found to increase with increasing organic content. The experimental results from stress paths at constant stress ratio reveal an anisotropic pre-failure plastic deformation mode, which depends on the previous stress history and loading direction. This suggests that the stress-dilatancy relationship cannot be formulated as a unique function of the stress ratio. The high-quality experimental data presented in the paper enlarge the database on soft organic soils in view of the development of advanced constitutive models.
{"title":"Deformational response of a marine silty-clay with varying organic content in the triaxial compression space.","authors":"Elisa Ponzoni, S. Muraro, A. Nocilla, C. Jommi","doi":"10.1139/cgj-2023-0058","DOIUrl":"https://doi.org/10.1139/cgj-2023-0058","url":null,"abstract":"This study characterises the effects of naturally varying organic content on the compression and shear behaviour of a marine silty-clay from the Netherlands. Index properties and mechanical properties are determined through laboratory tests, including oedometer and multistage loading-unloading triaxial stress paths. The results indicate a significant impact of the organic content on the compression response, with both the loading and reloading indexes increasing as the loss on ignition increases from 3% to 7%. Additionally, the study suggests a directional response of the compression behaviour, with the loading index increasing with the stress ratio. The influence of the organic content on shear strength appears to be less significant. No brittle response is observed during shearing and a similar ultimate stress ratio is attained by all samples. However, a unique critical state line can only be identified for samples with similar organic content, as its intercept and slope are found to increase with increasing organic content. The experimental results from stress paths at constant stress ratio reveal an anisotropic pre-failure plastic deformation mode, which depends on the previous stress history and loading direction. This suggests that the stress-dilatancy relationship cannot be formulated as a unique function of the stress ratio. The high-quality experimental data presented in the paper enlarge the database on soft organic soils in view of the development of advanced constitutive models.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2023-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139214962","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}
Abedalqader Idries, Timothy D. Stark, Lucia Moya, Jiale Lin
Canadian Geotechnical Journal, Ahead of Print. Water infiltration can cause softening of compacted structural fill and a reduction of the shear strength from the peak compacted strength to the fully softened strength (FSS) with an accompanying reduction in drained factor of safety (FoS). This study presents two-dimensional (2D) and 3D stability analyses of a compacted fill slope failure that occurred 6 years after construction due to water leaking from a connection between the main and lateral water pipes in the water supply system. The compacted fill material primarily consists of high plasticity fine-grained soil. The 3D FoS at the end of construction is 2.44 using the peak compacted strength envelope. However, the 3D FoS is close to unity (1.0) when the FSS is assigned to the compacted fill material with the appropriate piezometric surface, which means the 2 H:1 V compacted fill slope softened to the FSS within 6 years. This is an interesting FSS case because the failure surface is 4 m deep and semi-circular, which differs from infiltration cases that exhibit a shallower and more planar surface.
{"title":"Case study: 3D mobilized strength of compacted fill","authors":"Abedalqader Idries, Timothy D. Stark, Lucia Moya, Jiale Lin","doi":"10.1139/cgj-2023-0187","DOIUrl":"https://doi.org/10.1139/cgj-2023-0187","url":null,"abstract":"Canadian Geotechnical Journal, Ahead of Print. <br/> Water infiltration can cause softening of compacted structural fill and a reduction of the shear strength from the peak compacted strength to the fully softened strength (FSS) with an accompanying reduction in drained factor of safety (FoS). This study presents two-dimensional (2D) and 3D stability analyses of a compacted fill slope failure that occurred 6 years after construction due to water leaking from a connection between the main and lateral water pipes in the water supply system. The compacted fill material primarily consists of high plasticity fine-grained soil. The 3D FoS at the end of construction is 2.44 using the peak compacted strength envelope. However, the 3D FoS is close to unity (1.0) when the FSS is assigned to the compacted fill material with the appropriate piezometric surface, which means the 2 H:1 V compacted fill slope softened to the FSS within 6 years. This is an interesting FSS case because the failure surface is 4 m deep and semi-circular, which differs from infiltration cases that exhibit a shallower and more planar surface.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2023-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140597860","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}
Xuesong Cheng, Linsong Zhao, Shengzhang Han, Yetao Ji, Zhaorong Xu, Lingbo Meng, Jun Pan, Gang Zheng, Ruikun Wang
Multi-row grouting can be used to repeatedly mitigate the deformation of critical structures like tunnels. Nevertheless, no comprehensive investigation into the development patterns of soil deformation and excess pore water pressure, induced by multi-row grouting in soft soil, has been conducted to date. To address this gap, this study carried out a field test of multi-row grouting, systematically exploring the evolution and accumulation of soil horizontal displacement (SHD) and excess pore water pressure (EPWP) resulting from multi-row grouting. The findings demonstrated that the grouting process during multi-row grouting respectively exerted reaction and shielding effects on the subsequent grouting for the behavior of soil surrounding the grouting area. The reaction and shielding effects increased proportionally with the number of grouted rows. To predict the SHD induced by multi-row grouting, considering the reaction and shielding effects, this study provided a theoretical calculation method based on cavity expansion theory and the concept of upper and lower bounds, and proposed an optimal grouting scheme.
{"title":"In-situ Test and Calculation Method for Horizontal Deformation of Soil Induced by Multi-row Grouting","authors":"Xuesong Cheng, Linsong Zhao, Shengzhang Han, Yetao Ji, Zhaorong Xu, Lingbo Meng, Jun Pan, Gang Zheng, Ruikun Wang","doi":"10.1139/cgj-2023-0394","DOIUrl":"https://doi.org/10.1139/cgj-2023-0394","url":null,"abstract":"Multi-row grouting can be used to repeatedly mitigate the deformation of critical structures like tunnels. Nevertheless, no comprehensive investigation into the development patterns of soil deformation and excess pore water pressure, induced by multi-row grouting in soft soil, has been conducted to date. To address this gap, this study carried out a field test of multi-row grouting, systematically exploring the evolution and accumulation of soil horizontal displacement (SHD) and excess pore water pressure (EPWP) resulting from multi-row grouting. The findings demonstrated that the grouting process during multi-row grouting respectively exerted reaction and shielding effects on the subsequent grouting for the behavior of soil surrounding the grouting area. The reaction and shielding effects increased proportionally with the number of grouted rows. To predict the SHD induced by multi-row grouting, considering the reaction and shielding effects, this study provided a theoretical calculation method based on cavity expansion theory and the concept of upper and lower bounds, and proposed an optimal grouting scheme.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2023-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139263136","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}
Zhaoyang Song, Tiantian Ma, Yan Liu, Guoqing Cai, Changfu Wei
Pore water chemistry can exert significant controls over the chemo-mechanical behavior of chemically-active soils, which has not been characterized by using the traditional Terzaghi’s effective stress to a satisfactory extent. In this paper, based on the concept of intergranular stress, the effective stress for saturated active soils is first reconceptualized and then incorporated into the framework of the modified Cam-Clay model to describe the mechanical response of soils upon complex chemical and mechanical loadings. The proposed model is capable of capturing very well the diverse features of the chemo-behavior of saturated active soils, while inheriting all the advantages of the MCC model, by introducing only one additional parameter. Within this context, a simple equation is derived to predict the development of swelling pressure with the variation of pore water chemistry. It is shown the proposed swelling-pressure equation predicts very well the development of swelling pressure for expansive soils with a dilute pore solution, though discrepancy appears at high concentration. Because the double layer of clay particles is severely suppressed at high salt concentration, the microfabric of soil can be significantly changed, pointing to the importance of taking into account the effect of soil fabric in the constitutive modeling of active soils with high pore water concentration.
{"title":"An effective stress-based approach to modeling the chemo-mechanical behavior of saturated active clay","authors":"Zhaoyang Song, Tiantian Ma, Yan Liu, Guoqing Cai, Changfu Wei","doi":"10.1139/cgj-2022-0233","DOIUrl":"https://doi.org/10.1139/cgj-2022-0233","url":null,"abstract":"Pore water chemistry can exert significant controls over the chemo-mechanical behavior of chemically-active soils, which has not been characterized by using the traditional Terzaghi’s effective stress to a satisfactory extent. In this paper, based on the concept of intergranular stress, the effective stress for saturated active soils is first reconceptualized and then incorporated into the framework of the modified Cam-Clay model to describe the mechanical response of soils upon complex chemical and mechanical loadings. The proposed model is capable of capturing very well the diverse features of the chemo-behavior of saturated active soils, while inheriting all the advantages of the MCC model, by introducing only one additional parameter. Within this context, a simple equation is derived to predict the development of swelling pressure with the variation of pore water chemistry. It is shown the proposed swelling-pressure equation predicts very well the development of swelling pressure for expansive soils with a dilute pore solution, though discrepancy appears at high concentration. Because the double layer of clay particles is severely suppressed at high salt concentration, the microfabric of soil can be significantly changed, pointing to the importance of taking into account the effect of soil fabric in the constitutive modeling of active soils with high pore water concentration.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2023-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139264613","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}
Mine tailings storage poses significant environmental risks such as the formation of acid mine drainage (AMD). Engineered covers offer a solution by controlling water ingress. Their performance is based on specific soil hydrogeological properties (SHPs). They must support vegetation which can impact saturated hydraulic conductivity (ksat) and water retention curve (WRC). This study assesses the impact of four-year-old willow root colonization on silty soil covers using flexible wall permeameters and water retention tests. The obtained SHPs were compared with root traits. Results suggested that the hydrogeological properties of the studied in situ samples were not significantly affected by roots. The variation of measured and predicted ksat values spanned an order of magnitude, regardless of the root colonization intensity, up to a root length density (RLD) of 2.98 cm/cm3. RLD showed a significant and positive linear relationship with measured ksat values (R2 = 0.54). However, when root colonization was low (RLD < 1 cm/cm3), RLD was negatively correlated to the nvg (R2 = 0.44) parameter of the van Genuchten WRC model, while the opposite relationship was observed for samples with RLD > 1 cm/cm3 (R2 = 0.61). Additionally, RLD and the coarse root (diameter > 1 mm) volume to fine root volume (C/F ratio) influenced WRCs. Over time, coarser roots may have a more pronounced impact on SHPs; further research is needed
{"title":"Impact of Roots on the Hydrogeological Properties of Silty Soil Covers","authors":"Alex Proteau, M. Guittonny, Bruno Bussière","doi":"10.1139/cgj-2023-0016","DOIUrl":"https://doi.org/10.1139/cgj-2023-0016","url":null,"abstract":"Mine tailings storage poses significant environmental risks such as the formation of acid mine drainage (AMD). Engineered covers offer a solution by controlling water ingress. Their performance is based on specific soil hydrogeological properties (SHPs). They must support vegetation which can impact saturated hydraulic conductivity (ksat) and water retention curve (WRC). This study assesses the impact of four-year-old willow root colonization on silty soil covers using flexible wall permeameters and water retention tests. The obtained SHPs were compared with root traits. Results suggested that the hydrogeological properties of the studied in situ samples were not significantly affected by roots. The variation of measured and predicted ksat values spanned an order of magnitude, regardless of the root colonization intensity, up to a root length density (RLD) of 2.98 cm/cm3. RLD showed a significant and positive linear relationship with measured ksat values (R2 = 0.54). However, when root colonization was low (RLD < 1 cm/cm3), RLD was negatively correlated to the nvg (R2 = 0.44) parameter of the van Genuchten WRC model, while the opposite relationship was observed for samples with RLD > 1 cm/cm3 (R2 = 0.61). Additionally, RLD and the coarse root (diameter > 1 mm) volume to fine root volume (C/F ratio) influenced WRCs. Over time, coarser roots may have a more pronounced impact on SHPs; further research is needed","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2023-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139274598","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}
Haiyi Zhong, Yikai Wang, Shuai Zhang, Qi Zhang, C.W.W. Ng
The extreme drought-rainfall seesaw is projected to occur with an increasing frequency. However, there still lacks a thorough understanding of its impacts on slope behaviour, in which desiccation crack plays a key role. To address this issue, a centrifuge test was conducted to investigate the effects of drought-induced desiccation crack on slope instability under extreme rainfall. During the test, the intact slope was firstly subjected to extreme rainfall with 100-year return period. Subsequently, a long-term drying was applied to induce desiccation crack, and hence forming a cracked slope. The cracked slope is then subjected to an identical extreme rainfall. The intact slope only exhibits swelling deformation, whereas for the cracked slope, a slip surface (2 m in depth) is clearly observed to initiate from one deep crack at crest. The global sliding failure of the cracked slope is mainly related to preferential flow, which could result in soil shear strength reduction.
{"title":"Effects of extreme drought-rainfall on slope failure mechanisms: centrifuge modelling","authors":"Haiyi Zhong, Yikai Wang, Shuai Zhang, Qi Zhang, C.W.W. Ng","doi":"10.1139/cgj-2023-0133","DOIUrl":"https://doi.org/10.1139/cgj-2023-0133","url":null,"abstract":"The extreme drought-rainfall seesaw is projected to occur with an increasing frequency. However, there still lacks a thorough understanding of its impacts on slope behaviour, in which desiccation crack plays a key role. To address this issue, a centrifuge test was conducted to investigate the effects of drought-induced desiccation crack on slope instability under extreme rainfall. During the test, the intact slope was firstly subjected to extreme rainfall with 100-year return period. Subsequently, a long-term drying was applied to induce desiccation crack, and hence forming a cracked slope. The cracked slope is then subjected to an identical extreme rainfall. The intact slope only exhibits swelling deformation, whereas for the cracked slope, a slip surface (2 m in depth) is clearly observed to initiate from one deep crack at crest. The global sliding failure of the cracked slope is mainly related to preferential flow, which could result in soil shear strength reduction.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134957573","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}
Tailings storage facilities (TSFs) have undergone an unacceptably high failure rate for decades, leading to an increased focus on improving the safety of these structures. One aspect that has not received sufficient attention is examining how reliably and consistently engineers analyse the stability of TSFs. An understanding of the current state of practice is needed as there are a range of analytical methods available to engineers, while the high failure rate of these structures strongly points to some deficiencies in practice. To examine some of these issues, a tailings-focussed slope stability comparative design exercise was organised to compare the methods and results used by tailings engineers to analyse the same slope within which the phreatic surface was to rise under a specified pattern. Twenty-eight practitioners participated in the exercise to predict at what phreatic surface level the slope would fail. A wide range of predictions were made, ranging from assuming the slope would liquefy and fail instantly (i.e. before any rise in phreatic surface), to a range of techniques based on (i) yield strength ratios, (ii) stress path methods, and (iii) numerical analyses, each predicting various failure levels, and finally some predictors who applied drained strengths, resulting in predictions that the slope would not fail.
{"title":"Development and outcomes of a tailings slope stability comparative design exercise","authors":"David Reid, Andy Fourie","doi":"10.1139/cgj-2022-0065","DOIUrl":"https://doi.org/10.1139/cgj-2022-0065","url":null,"abstract":"Tailings storage facilities (TSFs) have undergone an unacceptably high failure rate for decades, leading to an increased focus on improving the safety of these structures. One aspect that has not received sufficient attention is examining how reliably and consistently engineers analyse the stability of TSFs. An understanding of the current state of practice is needed as there are a range of analytical methods available to engineers, while the high failure rate of these structures strongly points to some deficiencies in practice. To examine some of these issues, a tailings-focussed slope stability comparative design exercise was organised to compare the methods and results used by tailings engineers to analyse the same slope within which the phreatic surface was to rise under a specified pattern. Twenty-eight practitioners participated in the exercise to predict at what phreatic surface level the slope would fail. A wide range of predictions were made, ranging from assuming the slope would liquefy and fail instantly (i.e. before any rise in phreatic surface), to a range of techniques based on (i) yield strength ratios, (ii) stress path methods, and (iii) numerical analyses, each predicting various failure levels, and finally some predictors who applied drained strengths, resulting in predictions that the slope would not fail.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135092262","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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