Abhishek Kumar Singh, S. Ram, Ashok Kumar, P. Waclawik, R. Kukutsch
Induced stress driven spalling in coal pillars depends on several factors including depth of cover, in-situ stresses and presence of weak planes. A solid coal pillar generally experiences spalling at a higher depth. Fender and snook/rib experiences considerable spalling during depillaring even at lower depth below strong and massive rock mass. The spalling in pillars leads to instability at working places including goaf encroachment during depillaring. This paper discusses the measurement of induced stress driven spalling during development of a seam having weak roof-pillar interface at 850-900 m at CSM mine in Czech Republic. Spalling is also examined in different form of coal pillars during mechanized depillaring at 250 m depth at Godavarikhani 11 Incline mine in India. Finite difference based numerical modelling was carried out to assess the behaviour of the pillars. Ultimate non-elastic region was observed up to 9 m near the roof-pillar interface due to presence of weak plane and around 8 m at middle height of the pillar at the higher depth. At the moderate depth of around 250 m, maximum vertical induced stress was observed over a fender. Spalling of 2 m and 1.5 m was observed in the fender and pillar respectively.
{"title":"Stability study of coal pillars due to induced stress driven spalling during development and mechanised depillaring at different depths of cover","authors":"Abhishek Kumar Singh, S. Ram, Ashok Kumar, P. Waclawik, R. Kukutsch","doi":"10.1139/cgj-2024-0114","DOIUrl":"https://doi.org/10.1139/cgj-2024-0114","url":null,"abstract":"Induced stress driven spalling in coal pillars depends on several factors including depth of cover, in-situ stresses and presence of weak planes. A solid coal pillar generally experiences spalling at a higher depth. Fender and snook/rib experiences considerable spalling during depillaring even at lower depth below strong and massive rock mass. The spalling in pillars leads to instability at working places including goaf encroachment during depillaring. This paper discusses the measurement of induced stress driven spalling during development of a seam having weak roof-pillar interface at 850-900 m at CSM mine in Czech Republic. Spalling is also examined in different form of coal pillars during mechanized depillaring at 250 m depth at Godavarikhani 11 Incline mine in India. Finite difference based numerical modelling was carried out to assess the behaviour of the pillars. Ultimate non-elastic region was observed up to 9 m near the roof-pillar interface due to presence of weak plane and around 8 m at middle height of the pillar at the higher depth. At the moderate depth of around 250 m, maximum vertical induced stress was observed over a fender. Spalling of 2 m and 1.5 m was observed in the fender and pillar respectively.","PeriodicalId":505159,"journal":{"name":"Canadian Geotechnical Journal","volume":" 13","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141825547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shima Rezaeian Niri, Ali Akhtarpour, Farzad Daliri, Mohammad Saleh Baradaran
Mining and using underground resources demand high water usage, producing significant waste with environmental risks. Methods like electrokinetics prove effective in accelerating dewatering and stabilizing structures. This research provides the results of experimental investigation on dewatering silty tailings obtained from Sungun Tailings Dam (East Azerbaijan, Iran) using the electrokinetic water recovery method. Previous studies primarily examined the electrokinetic process in steady-state flow and saturated soil, with limited exploration of unsaturated soil parameters. In this research, the electrokinetic process in steady-state flow was initially investigated, and the saturated electro-osmotic permeability was determined. Subsequently, experiments were conducted in non-steady-state flow and unsaturated conditions, measuring the influential parameters with soil moisture sensors and tensiometers. Results show that decreasing sample moisture through electro-osmotic flow increases negative pore water pressure. Tailings' electrical conductivity is more influenced by moisture content, with a steeper reduction slope concerning volumetric moisture reduction over time. pH assessments show soil acidity at anode side and alkalinity on the cathode side. Higher applied voltage increasing maximum power consumption. Importantly, the results caution against assuming that higher applied voltage improves the electro-osmotic process, as it may lead to issues such as deep sample cracking; void space creation, interrupted electrical flow, and energy loss.
{"title":"Experimental investigation of dewatering silty tailings using electrokinetic method","authors":"Shima Rezaeian Niri, Ali Akhtarpour, Farzad Daliri, Mohammad Saleh Baradaran","doi":"10.1139/cgj-2024-0069","DOIUrl":"https://doi.org/10.1139/cgj-2024-0069","url":null,"abstract":"Mining and using underground resources demand high water usage, producing significant waste with environmental risks. Methods like electrokinetics prove effective in accelerating dewatering and stabilizing structures. This research provides the results of experimental investigation on dewatering silty tailings obtained from Sungun Tailings Dam (East Azerbaijan, Iran) using the electrokinetic water recovery method. Previous studies primarily examined the electrokinetic process in steady-state flow and saturated soil, with limited exploration of unsaturated soil parameters. In this research, the electrokinetic process in steady-state flow was initially investigated, and the saturated electro-osmotic permeability was determined. Subsequently, experiments were conducted in non-steady-state flow and unsaturated conditions, measuring the influential parameters with soil moisture sensors and tensiometers. Results show that decreasing sample moisture through electro-osmotic flow increases negative pore water pressure. Tailings' electrical conductivity is more influenced by moisture content, with a steeper reduction slope concerning volumetric moisture reduction over time. pH assessments show soil acidity at anode side and alkalinity on the cathode side. Higher applied voltage increasing maximum power consumption. Importantly, the results caution against assuming that higher applied voltage improves the electro-osmotic process, as it may lead to issues such as deep sample cracking; void space creation, interrupted electrical flow, and energy loss.","PeriodicalId":505159,"journal":{"name":"Canadian Geotechnical Journal","volume":" 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141831596","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M.M.A.L.N. Maheepala, M. C. M. Nasvi, D. Robert, C. Gunasekara, L. C. Kurukulasuriya
Extensive areal distribution of expansive soil is a timely concern in engineering challenges. Geopolymers outperform conventional cement/lime treatment in expansive soil stabilization due to their superior mechanical and durability performance. However, the excessive cost and carbon footprint of commercial alkaline activators hinder geopolymer's widespread application. This study aims to derive a cost-effective, carbon-conscious mix to stabilize expansive soil using waste-based geopolymerization. Class F fly ash was activated via a novel solution of rice husk ash (RHA)-derived silicate and NaOH. Three factors (NaOH/RHA, NaOH molarity, mixing duration) were considered using the Taguchi method and utility concept for mix optimization, while further investigations were tailored to explore the effects of curing temperature (room temperature, 30 °C, and 40 °C) and the curing period (7, 14, and 28 days) on the strength development of treated soil. The results indicate that NaOH/RHA = 0.6, NaOH molarity = 3 mol/L, and a mixing duration of 40 min with curing temperatures of around 30 °C are ideal for maximizing the strength cost-effectively while significantly reducing the swell pressure (up to 28%). The shift from commercial Na2SiO3 to RHA-silicate is 89% cheaper and reduces the carbon footprint by 70%. The study benefits sustainable ground stabilization and efficient waste management.
{"title":"Mix optimization for expansive soil stabilized with a novel waste material-based geopolymerization approach","authors":"M.M.A.L.N. Maheepala, M. C. M. Nasvi, D. Robert, C. Gunasekara, L. C. Kurukulasuriya","doi":"10.1139/cgj-2023-0271","DOIUrl":"https://doi.org/10.1139/cgj-2023-0271","url":null,"abstract":"Extensive areal distribution of expansive soil is a timely concern in engineering challenges. Geopolymers outperform conventional cement/lime treatment in expansive soil stabilization due to their superior mechanical and durability performance. However, the excessive cost and carbon footprint of commercial alkaline activators hinder geopolymer's widespread application. This study aims to derive a cost-effective, carbon-conscious mix to stabilize expansive soil using waste-based geopolymerization. Class F fly ash was activated via a novel solution of rice husk ash (RHA)-derived silicate and NaOH. Three factors (NaOH/RHA, NaOH molarity, mixing duration) were considered using the Taguchi method and utility concept for mix optimization, while further investigations were tailored to explore the effects of curing temperature (room temperature, 30 °C, and 40 °C) and the curing period (7, 14, and 28 days) on the strength development of treated soil. The results indicate that NaOH/RHA = 0.6, NaOH molarity = 3 mol/L, and a mixing duration of 40 min with curing temperatures of around 30 °C are ideal for maximizing the strength cost-effectively while significantly reducing the swell pressure (up to 28%). The shift from commercial Na2SiO3 to RHA-silicate is 89% cheaper and reduces the carbon footprint by 70%. The study benefits sustainable ground stabilization and efficient waste management.","PeriodicalId":505159,"journal":{"name":"Canadian Geotechnical Journal","volume":" 22","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141373624","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Junlin Rong, Majidreza Nazem, Shiao Huey Chow, Annan Zhou, Sara Moridpour
This study investigates the applicability of a speargun projectile penetrometer (SPP) for offshore site investigation purposes using experimental testing. The SPP can shoot penetrometers using an elastic/pneumatic force. The speargun is easy to handle, can generate significant kinetic energy and requires a single operator to perform the test. A laboratory test platform was utilised to hold the SPP and ensure vertical launch, while a laser displacement sensor was employed to monitor the penetration depth and record the corresponding time history. The result demonstrated that the speargun-launched method achieves significantly higher embedment depth compared to an equivalent free-falling penetrometer. In particular, the new method produces sufficiently deep penetration in dense sand thus overcoming the typical penetrometer tilting issue caused by shallow penetration. These findings provide a preliminary insight into the speargun projectile penetrometer, allowing for exploration beyond the boundaries of traditional penetrometers in laboratory testing and offshore site investigation.
{"title":"Development of a Speargun Projectile Penetrometer in Soil","authors":"Junlin Rong, Majidreza Nazem, Shiao Huey Chow, Annan Zhou, Sara Moridpour","doi":"10.1139/cgj-2023-0732","DOIUrl":"https://doi.org/10.1139/cgj-2023-0732","url":null,"abstract":"This study investigates the applicability of a speargun projectile penetrometer (SPP) for offshore site investigation purposes using experimental testing. The SPP can shoot penetrometers using an elastic/pneumatic force. The speargun is easy to handle, can generate significant kinetic energy and requires a single operator to perform the test. A laboratory test platform was utilised to hold the SPP and ensure vertical launch, while a laser displacement sensor was employed to monitor the penetration depth and record the corresponding time history. The result demonstrated that the speargun-launched method achieves significantly higher embedment depth compared to an equivalent free-falling penetrometer. In particular, the new method produces sufficiently deep penetration in dense sand thus overcoming the typical penetrometer tilting issue caused by shallow penetration. These findings provide a preliminary insight into the speargun projectile penetrometer, allowing for exploration beyond the boundaries of traditional penetrometers in laboratory testing and offshore site investigation.","PeriodicalId":505159,"journal":{"name":"Canadian Geotechnical Journal","volume":"3 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141383804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In slurry-shield tunnelling, a heterogeneous dynamic filter cake occurs due to the interaction between slurry infiltrating and tool cutting, whose influence on tunnel face stability is not fully plumbed. Thus, a numerically based-limit analysis framework is proposed to assess the tunnel face stability considering a heterogeneous dynamic filter cake. The numerical model with a heterogeneous dynamic filter cake, which has spatio-temporally variable permeability coefficients according to cutter layouts, is built for solving a transient seepage flow. Numerically obtained seepage flow results are further incorporated into the 3D rotational failure mechanism, so as to give an upper-bound estimation on the tunnel face safety factor and the slurry pressure transfer efficiency. The proposed method is validated by comparing with previous studies regarding the slurry pressure drop, slurry pressure transfer efficiency, and tunnel face safety factors. Parametric analyses are performed to examine the excess pore pressure distributions at the filter cake-soil interface, and discuss the influences of cutterhead rotation and excess slurry pressures on the tunnel face stability. The results show that the defined three-dimensional pressure transfer efficiency is between the one-dimensional and the two-dimensional solutions published previously; the tunnel face stability reduces as cutterhead rotating and finally reaches a dynamic equilibrium state.
{"title":"Three-dimensional tunnel face stability using a new heterogeneous dynamic filter cake","authors":"Qiujing Pan, C. Hou, Hao Xiong, Zihan Yang","doi":"10.1139/cgj-2023-0085","DOIUrl":"https://doi.org/10.1139/cgj-2023-0085","url":null,"abstract":"In slurry-shield tunnelling, a heterogeneous dynamic filter cake occurs due to the interaction between slurry infiltrating and tool cutting, whose influence on tunnel face stability is not fully plumbed. Thus, a numerically based-limit analysis framework is proposed to assess the tunnel face stability considering a heterogeneous dynamic filter cake. The numerical model with a heterogeneous dynamic filter cake, which has spatio-temporally variable permeability coefficients according to cutter layouts, is built for solving a transient seepage flow. Numerically obtained seepage flow results are further incorporated into the 3D rotational failure mechanism, so as to give an upper-bound estimation on the tunnel face safety factor and the slurry pressure transfer efficiency. The proposed method is validated by comparing with previous studies regarding the slurry pressure drop, slurry pressure transfer efficiency, and tunnel face safety factors. Parametric analyses are performed to examine the excess pore pressure distributions at the filter cake-soil interface, and discuss the influences of cutterhead rotation and excess slurry pressures on the tunnel face stability. The results show that the defined three-dimensional pressure transfer efficiency is between the one-dimensional and the two-dimensional solutions published previously; the tunnel face stability reduces as cutterhead rotating and finally reaches a dynamic equilibrium state.","PeriodicalId":505159,"journal":{"name":"Canadian Geotechnical Journal","volume":"17 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141383569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hydrochar, which is produced by hydrothermal carbonisation, is an alternative to biochar for the alleviation of plant water stress. However, hydrochar shows vulnerability to decomposition. This study measured the effects of grass-derived hydrochar on hysteretic wide-suction range water retention curves (WRCs) of compacted soils and investigated how hydrochar decomposition affected the WRCs and pore size distributions. Hydrochar addition increased the first air-entry value (AEV) at a relatively low suction range due to the reduction in the macro-pore peak diameter but reduced the second AEV at a higher suction range following the increase in pore volume at diameters larger than 0.3 µm. A strongly positive correlation existed between the AEVs and the peaks of the degree of hysteresis, which suggests that the peak hysteresis is related to the ink-bottle effect despite the modification of soil pore structure due to hydrochar addition. After 120 days of decomposition to an approximately stable state, the hydrochar did not affect all the WRCs at a wide suction range, regardless of the emergence of bacteria and fungi. The test results highlight the potential of hydrochar in promoting plant growth through improvements of the soil’s WRCs and the increase in abundance of functional bacteria and fungi.
{"title":"Wide-suction-range hysteretic water retention behaviour of compacted soils amended by decomposing hydrochar","authors":"Huan Dong, Anthony Kwan Leung, Rui Chen","doi":"10.1139/cgj-2023-0739","DOIUrl":"https://doi.org/10.1139/cgj-2023-0739","url":null,"abstract":"Hydrochar, which is produced by hydrothermal carbonisation, is an alternative to biochar for the alleviation of plant water stress. However, hydrochar shows vulnerability to decomposition. This study measured the effects of grass-derived hydrochar on hysteretic wide-suction range water retention curves (WRCs) of compacted soils and investigated how hydrochar decomposition affected the WRCs and pore size distributions. Hydrochar addition increased the first air-entry value (AEV) at a relatively low suction range due to the reduction in the macro-pore peak diameter but reduced the second AEV at a higher suction range following the increase in pore volume at diameters larger than 0.3 µm. A strongly positive correlation existed between the AEVs and the peaks of the degree of hysteresis, which suggests that the peak hysteresis is related to the ink-bottle effect despite the modification of soil pore structure due to hydrochar addition. After 120 days of decomposition to an approximately stable state, the hydrochar did not affect all the WRCs at a wide suction range, regardless of the emergence of bacteria and fungi. The test results highlight the potential of hydrochar in promoting plant growth through improvements of the soil’s WRCs and the increase in abundance of functional bacteria and fungi.","PeriodicalId":505159,"journal":{"name":"Canadian Geotechnical Journal","volume":"38 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141414810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The residual shear strength (RSS) of unsaturated soils is a crucial parameter for the reliable analysis and design of geo-structures constructed with or within unsaturated soils undergoing large shear deformation. For investigating the RSS of unsaturated soils, two sets of data are specifically generated on the SP-SM and Indian Head till using suction-controlled ring shear tests and three more sets (i.e., SM, SC-SM and CH) are gathered from the literature. A model is proposed extending two approaches for predicting the RSS for both coarse- and fine-grained unsaturated soils. In this model, the suction contribution was calculated considering the loss of degree of saturation due to shearing, which was described as a nonlinear function of degree of saturation. The capability of the proposed model is validated with the five sets of data using two different approaches. The best-fitting approach that is based on three fitting parameters provides good predictions. The approximate approach performs well for four studied soils, except for SM soil; this approach is simple for use in engineering practice because no fitting parameters are required. The proposed model is valid for the suction range where degree of saturation is higher than the residual degree of saturation.
非饱和土壤的残余剪切强度（RSS）是可靠分析和设计在非饱和土壤中或在非饱和土壤中承受大剪切变形的土工结构的关键参数。为研究非饱和土的 RSS，利用吸力控制环剪试验专门生成了 SP-SM 和 Indian Head till 的两组数据，并从文献中收集了另外三组数据（即 SM、SC-SM 和 CH）。提出了一个模型，扩展了两种预测粗粒和细粒非饱和土壤 RSS 的方法。在该模型中，吸力贡献的计算考虑了剪切造成的饱和度损失，并将其描述为饱和度的非线性函数。使用两种不同的方法，利用五组数据验证了拟议模型的能力。基于三个拟合参数的最佳拟合方法提供了良好的预测。除 SM 土外，近似法对所研究的四种土壤都有很好的效果；由于不需要拟合参数，这种方法在工程实践中使用起来很简单。建议的模型适用于饱和度高于残余饱和度的吸力范围。
{"title":"Model for the Prediction of Residual Shear Strength of Unsaturated Soils","authors":"Xiuhan Yang, Sai Vanapalli","doi":"10.1139/cgj-2023-0561","DOIUrl":"https://doi.org/10.1139/cgj-2023-0561","url":null,"abstract":"The residual shear strength (RSS) of unsaturated soils is a crucial parameter for the reliable analysis and design of geo-structures constructed with or within unsaturated soils undergoing large shear deformation. For investigating the RSS of unsaturated soils, two sets of data are specifically generated on the SP-SM and Indian Head till using suction-controlled ring shear tests and three more sets (i.e., SM, SC-SM and CH) are gathered from the literature. A model is proposed extending two approaches for predicting the RSS for both coarse- and fine-grained unsaturated soils. In this model, the suction contribution was calculated considering the loss of degree of saturation due to shearing, which was described as a nonlinear function of degree of saturation. The capability of the proposed model is validated with the five sets of data using two different approaches. The best-fitting approach that is based on three fitting parameters provides good predictions. The approximate approach performs well for four studied soils, except for SM soil; this approach is simple for use in engineering practice because no fitting parameters are required. The proposed model is valid for the suction range where degree of saturation is higher than the residual degree of saturation.","PeriodicalId":505159,"journal":{"name":"Canadian Geotechnical Journal","volume":"31 23","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141232972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yan Li, Xiaokun Hou, Tong-lu Li, Sai Vanapalli, Ping Li
The hydraulic conductivity function (HCF) refers to in this paper is the variation of hydraulic conductivity over the entire suction range from 0 to 106 kPa. Most of the available HCF models in the literature are derived based on capillary theory and have limitations in the explanation of HCF in the high suction range. Recently, several models have been proposed for accounting for the thin film flow dominated by the adsorbed water in the high suction range. However, these models require measured HCF data for describing the thin film flow, which is time-consuming. In this study, a mathematically continuous and simple model is proposed for predicting the HCF. The model has physically meaningful parameters for predicting the HCF. In this model, the residual suction estimated from the soil-water characteristic curve (SWCC) is used to distinguish the capillary and adsorption-dominated regions, and a correction operator that considers the thin film flow is introduced. The performance of the model was validated using the measured and published experimental data for various soils. In addition, the proposed model is successfully applied in a numerical investigation of the hydraulic behavior of a capillary barrier system, highlighting the role of the thin film flow.
{"title":"Prediction of the hydraulic conductivity function for unsaturated soils over the entire suction range","authors":"Yan Li, Xiaokun Hou, Tong-lu Li, Sai Vanapalli, Ping Li","doi":"10.1139/cgj-2023-0631","DOIUrl":"https://doi.org/10.1139/cgj-2023-0631","url":null,"abstract":"The hydraulic conductivity function (HCF) refers to in this paper is the variation of hydraulic conductivity over the entire suction range from 0 to 106 kPa. Most of the available HCF models in the literature are derived based on capillary theory and have limitations in the explanation of HCF in the high suction range. Recently, several models have been proposed for accounting for the thin film flow dominated by the adsorbed water in the high suction range. However, these models require measured HCF data for describing the thin film flow, which is time-consuming. In this study, a mathematically continuous and simple model is proposed for predicting the HCF. The model has physically meaningful parameters for predicting the HCF. In this model, the residual suction estimated from the soil-water characteristic curve (SWCC) is used to distinguish the capillary and adsorption-dominated regions, and a correction operator that considers the thin film flow is introduced. The performance of the model was validated using the measured and published experimental data for various soils. In addition, the proposed model is successfully applied in a numerical investigation of the hydraulic behavior of a capillary barrier system, highlighting the role of the thin film flow.","PeriodicalId":505159,"journal":{"name":"Canadian Geotechnical Journal","volume":"65 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140368847","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The effective thermal conductivity of soil is important to geo-engineering applications, and it is controlled by factors across different length scales. Through a comprehensive review of these factors, we found that while other more traditional factors have been well studied, there is still a lack of characterisation of soil microscale and mesoscale structures and their influence on effective thermal conductivity. In addition, after reviewing the models available in the literature for soil effective thermal conductivity prediction, it was found that compared with empirical and theoretical models, machine learning models can account for the influence of multi-scale factors, however, research into them is scarce. To overcome the limitations of previous research, we proposed a framework that can investigate the factors influencing soil effective thermal conductivity at multiple scale. It includes the impact of soil structural factors at micro to mesoscale, and this impact is integrated with the influence from other factors for accurate thermal conductivity prediction.
{"title":"Effective thermal conductivity of granular soils: a review of influencing factors and prediction models towards an investigation framework through multiscale characters","authors":"Tairu Chen, Wenbin Fei, Guillermo Narsilio","doi":"10.1139/cgj-2023-0465","DOIUrl":"https://doi.org/10.1139/cgj-2023-0465","url":null,"abstract":"The effective thermal conductivity of soil is important to geo-engineering applications, and it is controlled by factors across different length scales. Through a comprehensive review of these factors, we found that while other more traditional factors have been well studied, there is still a lack of characterisation of soil microscale and mesoscale structures and their influence on effective thermal conductivity. In addition, after reviewing the models available in the literature for soil effective thermal conductivity prediction, it was found that compared with empirical and theoretical models, machine learning models can account for the influence of multi-scale factors, however, research into them is scarce. To overcome the limitations of previous research, we proposed a framework that can investigate the factors influencing soil effective thermal conductivity at multiple scale. It includes the impact of soil structural factors at micro to mesoscale, and this impact is integrated with the influence from other factors for accurate thermal conductivity prediction.","PeriodicalId":505159,"journal":{"name":"Canadian Geotechnical Journal","volume":" 514","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140382939","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yuhan Yang, Chao Zhang, L. Gou, Yi Dong, Renpeng Chen
Soil desiccation crack is ubiquitous in nature, yet the physics of its initiation and propagation remain under debate, as it involves complex interactions across multiple fields of mechanics, hydraulics, and thermals. Here, an experimental attempt is made to uncover the role of substrate roughness on the soil desiccation process. The substrate roughness is deliberately fabricated by 3D printing, whereas the thickness of sample and environmental humidity are controlled to eliminate the effect of large hydraulic gradient. Four types of soils with varying expansibilities were desiccated on substrates with varying roughness. It reveals that: (1) soil desiccation crack evolution can be conceived as a competing process between the shear failure of soil-substrate interface, i.e., slippage of interface, and the tensile failure of soil, i.e., crack initiation, in minimizing the total energy of drying soil; (2) substrate roughness alters the failure mode and shear strength of soil-substrate interface and its sensitivity to moisture, thereby it regulates the pattern of how soil crack propagates upon drying; (3) soil expansibility is recognized as a key factor governing the crack-initiation point in addition to the widely recognized air-entry, and flaws in soil are the sources for the 120° crack angle and bimodal crack angle distribution.
{"title":"Role of Substrate Roughness in Soil Desiccation Cracking","authors":"Yuhan Yang, Chao Zhang, L. Gou, Yi Dong, Renpeng Chen","doi":"10.1139/cgj-2023-0638","DOIUrl":"https://doi.org/10.1139/cgj-2023-0638","url":null,"abstract":"Soil desiccation crack is ubiquitous in nature, yet the physics of its initiation and propagation remain under debate, as it involves complex interactions across multiple fields of mechanics, hydraulics, and thermals. Here, an experimental attempt is made to uncover the role of substrate roughness on the soil desiccation process. The substrate roughness is deliberately fabricated by 3D printing, whereas the thickness of sample and environmental humidity are controlled to eliminate the effect of large hydraulic gradient. Four types of soils with varying expansibilities were desiccated on substrates with varying roughness. It reveals that: (1) soil desiccation crack evolution can be conceived as a competing process between the shear failure of soil-substrate interface, i.e., slippage of interface, and the tensile failure of soil, i.e., crack initiation, in minimizing the total energy of drying soil; (2) substrate roughness alters the failure mode and shear strength of soil-substrate interface and its sensitivity to moisture, thereby it regulates the pattern of how soil crack propagates upon drying; (3) soil expansibility is recognized as a key factor governing the crack-initiation point in addition to the widely recognized air-entry, and flaws in soil are the sources for the 120° crack angle and bimodal crack angle distribution.","PeriodicalId":505159,"journal":{"name":"Canadian Geotechnical Journal","volume":"20 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140087678","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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