Water content is a fundamental parameter for analysing soil composition and engineering behaviour. However, conceptual water content sensors cannot be used in high-temperature and high-pressure environments. To assess the suitability of using electrical conductivity (EC) as a predictor of soil water content at high temperatures, a series of EC and water content tests of clay and sand is conducted. Subsequently, the relationships between EC and water content at different temperatures are analysed. On this basis, the feasibility of eight EC models for predicting soil water content is discussed. The results show that temperature has a vital impact on the EC test of soil and EC is more sensitive to temperature than to dry density and water content. The temperature effect of soil EC is more obvious with an increase in dry density, and EC does not increase monotonically with an increase in temperature. The predicted effect of some EC models tends to be better with an increase in dry density or temperature. This research provides a reference for the EC test and model establishment of high-temperature soils.
{"title":"Temperature-dependent relationship between the water content and electrical conductivity of soils","authors":"Zhixiang Chen, Huayue Yu, Yong Wan, Xingxing He, Longfei Hua","doi":"10.1680/jenge.23.00013","DOIUrl":"https://doi.org/10.1680/jenge.23.00013","url":null,"abstract":"Water content is a fundamental parameter for analysing soil composition and engineering behaviour. However, conceptual water content sensors cannot be used in high-temperature and high-pressure environments. To assess the suitability of using electrical conductivity (EC) as a predictor of soil water content at high temperatures, a series of EC and water content tests of clay and sand is conducted. Subsequently, the relationships between EC and water content at different temperatures are analysed. On this basis, the feasibility of eight EC models for predicting soil water content is discussed. The results show that temperature has a vital impact on the EC test of soil and EC is more sensitive to temperature than to dry density and water content. The temperature effect of soil EC is more obvious with an increase in dry density, and EC does not increase monotonically with an increase in temperature. The predicted effect of some EC models tends to be better with an increase in dry density or temperature. This research provides a reference for the EC test and model establishment of high-temperature soils.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"2012 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135548627","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Aircraft operations at an airport result in the emission of various substances. Simultaneously, in an airport area, road traffic is very intense, also contributing to the emission of the same substances. In this work, potentially toxic elements (PTEs), essentially trace metals, and others not categorized as such (alloys elements and ceramic particles that constitute particulate matter) are considered, which end up being deposited on soils. The main purpose of this study is to identify soil quality degradation potentially connected to aircraft operations related to Lisbon Airport. At the same time, an attempt is made to differentiate the contribution of soil quality degradation resulting from road traffic. Several geotechnical and chemical parameters are determined for all the 102 collected samples. X-ray fluorescence analysis is performed to identify and quantify the main elements present in all samples. Some samples are also subjected to X-ray diffraction to determine the mineralogical composition. The data obtained allow the creation of distribution maps of the detected elements and, after multivariate statistical analysis, conclude which ones are related to very intense road traffic and which ones are related to aircraft-traffic emissions, in an urban area, based on a holistic interpretation of all intervenient variables.
{"title":"Degradation of urban soil quality due to air and road traffic - relevant info and research","authors":"Celeste Jorge","doi":"10.1680/jenge.22.00043","DOIUrl":"https://doi.org/10.1680/jenge.22.00043","url":null,"abstract":"Aircraft operations at an airport result in the emission of various substances. Simultaneously, in an airport area, road traffic is very intense, also contributing to the emission of the same substances. In this work, potentially toxic elements (PTEs), essentially trace metals, and others not categorized as such (alloys elements and ceramic particles that constitute particulate matter) are considered, which end up being deposited on soils. The main purpose of this study is to identify soil quality degradation potentially connected to aircraft operations related to Lisbon Airport. At the same time, an attempt is made to differentiate the contribution of soil quality degradation resulting from road traffic. Several geotechnical and chemical parameters are determined for all the 102 collected samples. X-ray fluorescence analysis is performed to identify and quantify the main elements present in all samples. Some samples are also subjected to X-ray diffraction to determine the mineralogical composition. The data obtained allow the creation of distribution maps of the detected elements and, after multivariate statistical analysis, conclude which ones are related to very intense road traffic and which ones are related to aircraft-traffic emissions, in an urban area, based on a holistic interpretation of all intervenient variables.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135592084","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kai Xu, Ming Huang, Jinxuan Zhang, Mingjuan Cui, Chaoshui Xu
The disposal of tailings in a safe and environmentally friendly manner has always been a challenging issue. The microbially induced carbonate precipitation (MICP) technique is used to stabilise tailings sands. MICP is an innovative soil stabilisation technology. However, its field application in tailings sands is limited due to the poor adaptability of non-native urease-producing bacteria (UPB) in different natural environments. In this study, the ultraviolet (UV) mutagenesis technology was used to improve the performance of indigenous UPB, sourced from a hot and humid area of China. Mechanical property tests and microscopic inspections were conducted to assess the feasibility and the effectiveness of the technology. The roles played by the UV-induced UPB in the processes of nucleation and crystal growth were revealed by scanning electron microscopy imaging. The impacts of elements contained in the tailings sands on the morphology of calcium carbonate crystals were studied with Raman spectroscopy and energy-dispersive X-ray spectroscopy. The precipitation pattern of calcium carbonate and the strength enhancement mechanism of bio-cemented tailings were analysed in detail. The stabilisation method of tailings sands described in this paper provides a new cost-effective approach to mitigating the environmental issues and safety risks associated with the storage of tailings.
{"title":"Bio-cementation of tailings sands using ultraviolet induced urease-producing bacteria and its biomineralization mechanism","authors":"Kai Xu, Ming Huang, Jinxuan Zhang, Mingjuan Cui, Chaoshui Xu","doi":"10.1680/jenge.22.00075","DOIUrl":"https://doi.org/10.1680/jenge.22.00075","url":null,"abstract":"The disposal of tailings in a safe and environmentally friendly manner has always been a challenging issue. The microbially induced carbonate precipitation (MICP) technique is used to stabilise tailings sands. MICP is an innovative soil stabilisation technology. However, its field application in tailings sands is limited due to the poor adaptability of non-native urease-producing bacteria (UPB) in different natural environments. In this study, the ultraviolet (UV) mutagenesis technology was used to improve the performance of indigenous UPB, sourced from a hot and humid area of China. Mechanical property tests and microscopic inspections were conducted to assess the feasibility and the effectiveness of the technology. The roles played by the UV-induced UPB in the processes of nucleation and crystal growth were revealed by scanning electron microscopy imaging. The impacts of elements contained in the tailings sands on the morphology of calcium carbonate crystals were studied with Raman spectroscopy and energy-dispersive X-ray spectroscopy. The precipitation pattern of calcium carbonate and the strength enhancement mechanism of bio-cemented tailings were analysed in detail. The stabilisation method of tailings sands described in this paper provides a new cost-effective approach to mitigating the environmental issues and safety risks associated with the storage of tailings.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135547537","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-01DOI: 10.3390/geotechnics3040055
Gábor Somodi, Balázs Vásárhelyi
The most common classification method of drill cores is the Rock Quality Designation (RQD) value, which indicates the percentage of rock cores longer than 10 cm in a given core section. This core logging procedure is the basic parameter in the most useful rock mass classification methods like Rock Mass Rate (RMR) and Rock Mass Quality (Q). It is also used to determine the Geological Strength Index (GSI), which has become widely used in the last 20 years. One of the basic problems of the RQD value is that it does not distinguish different rock cores longer than 10 cm (100% is obtained for one piece of 1 m length and 10 pieces of 10 cm length) and a uniform result is obtained for shorter units. In this paper, the so-called Integrated RQD (Int_RQD) factor is introduced to eliminate these problems and to provide a better description of fracture density in the core logging procedure. As it uses the original core logging procedure, historical RQD data can also be reevaluated. Considering that RQD is an input parameter for most rock engineering classifications, these systems such as GSI can be reviewed based on the new RQD definition proposed herein.
{"title":"Borehole Analysis with the Modification of RQD Value","authors":"Gábor Somodi, Balázs Vásárhelyi","doi":"10.3390/geotechnics3040055","DOIUrl":"https://doi.org/10.3390/geotechnics3040055","url":null,"abstract":"The most common classification method of drill cores is the Rock Quality Designation (RQD) value, which indicates the percentage of rock cores longer than 10 cm in a given core section. This core logging procedure is the basic parameter in the most useful rock mass classification methods like Rock Mass Rate (RMR) and Rock Mass Quality (Q). It is also used to determine the Geological Strength Index (GSI), which has become widely used in the last 20 years. One of the basic problems of the RQD value is that it does not distinguish different rock cores longer than 10 cm (100% is obtained for one piece of 1 m length and 10 pieces of 10 cm length) and a uniform result is obtained for shorter units. In this paper, the so-called Integrated RQD (Int_RQD) factor is introduced to eliminate these problems and to provide a better description of fracture density in the core logging procedure. As it uses the original core logging procedure, historical RQD data can also be reevaluated. Considering that RQD is an input parameter for most rock engineering classifications, these systems such as GSI can be reviewed based on the new RQD definition proposed herein.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135457751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-01DOI: 10.3390/geotechnics3040054
Giseok Heo, Jaehwi Kim, Seokho Jeong, Dongyoup Kwak
This study evaluates the effectiveness of the previously proposed Standard Penetration Test (SPT) N and shear wave velocity (VS) models in relation to the geological attributes of the Busan region, situated in the southeastern part of the Korean peninsula. The multiple empirical N-VS models, which used datasets collected from different regions in South Korea, resulted in distinct N-VS trends across models. To validate the predictive capabilities of each model, this study gathered boring logs containing SPT N and VS measurements within the Busan region, followed by a thorough residual analysis. The Busan area encompasses a delta region to the west and erosion basins within the mountains and hills to the east. Despite the relatively confined geographical scope, we found that models developed using data from fill areas exhibit superior performance for the delta region (western Busan), while models constructed from datasets within erosion basins perform better for the erosion basin region (eastern Busan). This comparative examination supports the dependence of the N-VS model on geologic attributes and offers the valuable insight that N-VS models developed with analogous geological attributes should be employed when estimating VS from SPT N values.
{"title":"Evaluation of Shear Wave Velocity Prediction Models from Standard Penetration Test N Values Depending on Geologic Attributes: A Case Study in Busan, South Korea","authors":"Giseok Heo, Jaehwi Kim, Seokho Jeong, Dongyoup Kwak","doi":"10.3390/geotechnics3040054","DOIUrl":"https://doi.org/10.3390/geotechnics3040054","url":null,"abstract":"This study evaluates the effectiveness of the previously proposed Standard Penetration Test (SPT) N and shear wave velocity (VS) models in relation to the geological attributes of the Busan region, situated in the southeastern part of the Korean peninsula. The multiple empirical N-VS models, which used datasets collected from different regions in South Korea, resulted in distinct N-VS trends across models. To validate the predictive capabilities of each model, this study gathered boring logs containing SPT N and VS measurements within the Busan region, followed by a thorough residual analysis. The Busan area encompasses a delta region to the west and erosion basins within the mountains and hills to the east. Despite the relatively confined geographical scope, we found that models developed using data from fill areas exhibit superior performance for the delta region (western Busan), while models constructed from datasets within erosion basins perform better for the erosion basin region (eastern Busan). This comparative examination supports the dependence of the N-VS model on geologic attributes and offers the valuable insight that N-VS models developed with analogous geological attributes should be employed when estimating VS from SPT N values.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135459216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-29DOI: 10.3390/geotechnics3040053
Mir Md. Tamim, Debakanta Mishra, Bhaskar C. S. Chittoori
The challenge of maintaining ride quality and serviceability in flexible pavements built over expansive soil deposits remains a critical concern for transportation agencies. These expansive subgrades exhibit swell-shrink behavior in response to moisture fluctuations, leading to differential heaving and subsequent costly maintenance. This paper explores the effectiveness of a Hybrid Geosynthetic Reinforcement System (HGRS)—a composite of geocell and geogrid—as a targeted mitigation strategy for differential heaving induced by expansive soils. A large-scale box test was designed to simulate a flexible pavement section, consisting solely of a base course layer and the underlying expansive subgrade. Four test conditions were investigated: an unreinforced control, a geocell-reinforced section, a geogrid-reinforced section, and an HGRS-reinforced section. Vertical displacements on the surface of the base course layer were longitudinally monitored and compared against the control. The results reveal that the use of geosynthetic reinforcements, and HGRS in particular, significantly mitigates both maximum surficial heave and differential swelling. Among the systems tested, flexible pavements featuring HGRS demonstrated the most effective performance in alleviating the challenges posed by expansive soil deposits.
{"title":"Effectiveness of Hybrid Geosynthetic Systems in Controlling Differential Heave in Flexible Pavements over Expansive Soils","authors":"Mir Md. Tamim, Debakanta Mishra, Bhaskar C. S. Chittoori","doi":"10.3390/geotechnics3040053","DOIUrl":"https://doi.org/10.3390/geotechnics3040053","url":null,"abstract":"The challenge of maintaining ride quality and serviceability in flexible pavements built over expansive soil deposits remains a critical concern for transportation agencies. These expansive subgrades exhibit swell-shrink behavior in response to moisture fluctuations, leading to differential heaving and subsequent costly maintenance. This paper explores the effectiveness of a Hybrid Geosynthetic Reinforcement System (HGRS)—a composite of geocell and geogrid—as a targeted mitigation strategy for differential heaving induced by expansive soils. A large-scale box test was designed to simulate a flexible pavement section, consisting solely of a base course layer and the underlying expansive subgrade. Four test conditions were investigated: an unreinforced control, a geocell-reinforced section, a geogrid-reinforced section, and an HGRS-reinforced section. Vertical displacements on the surface of the base course layer were longitudinally monitored and compared against the control. The results reveal that the use of geosynthetic reinforcements, and HGRS in particular, significantly mitigates both maximum surficial heave and differential swelling. Among the systems tested, flexible pavements featuring HGRS demonstrated the most effective performance in alleviating the challenges posed by expansive soil deposits.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135246426","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ground source energy systems provide low-carbon heating and cooling to buildings, but their efficient deployment requires a reliable estimate of their thermal performance. A simplified methodology is presented to determine the thermal performance of thermo-active piles when heating or cooling loads are specified with either inlet pipe temperatures or imposed heat fluxes. The proposed methodology avoids computationally expensive 3D analyses and the explicit simulation of heat exchanger pipes, relying instead on 2D thermal analyses. When the heating or cooling of a thermo-active pile is assessed by imposing inlet pipe temperatures, the proposed methodology allows the determination of the power of pile per unit length. Conversely, when heating or cooling loads are specified via extracted or injected heat fluxes, the inlet and outlet fluid temperatures, as well as average temperatures at pile wall, are determined. The proposed methodology has been shown to reproduce accurately the thermal performance of thermo-active piles modelled using 3D analyses where heat exchanger pipes are explicitly simulated, considering different patterns of heating and cooling cycles. The application of the proposed methodology to the case of a real thermo-active pile is demonstrated by comparing its predicted thermal performance with the results of a well-documented field thermal response test.
{"title":"An assessment of a simplified methodology for determining the thermal performance of thermo-active piles","authors":"Ryan Yin Wai Liu, David MG Taborda","doi":"10.1680/jenge.22.00199","DOIUrl":"https://doi.org/10.1680/jenge.22.00199","url":null,"abstract":"Ground source energy systems provide low-carbon heating and cooling to buildings, but their efficient deployment requires a reliable estimate of their thermal performance. A simplified methodology is presented to determine the thermal performance of thermo-active piles when heating or cooling loads are specified with either inlet pipe temperatures or imposed heat fluxes. The proposed methodology avoids computationally expensive 3D analyses and the explicit simulation of heat exchanger pipes, relying instead on 2D thermal analyses. When the heating or cooling of a thermo-active pile is assessed by imposing inlet pipe temperatures, the proposed methodology allows the determination of the power of pile per unit length. Conversely, when heating or cooling loads are specified via extracted or injected heat fluxes, the inlet and outlet fluid temperatures, as well as average temperatures at pile wall, are determined. The proposed methodology has been shown to reproduce accurately the thermal performance of thermo-active piles modelled using 3D analyses where heat exchanger pipes are explicitly simulated, considering different patterns of heating and cooling cycles. The application of the proposed methodology to the case of a real thermo-active pile is demonstrated by comparing its predicted thermal performance with the results of a well-documented field thermal response test.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135344572","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-24DOI: 10.3390/geotechnics3040052
Ambrosios-Antonios Savvides, Andreas A. Antoniou, Leonidas Papadopoulos, Anastasia Monia, Kalliopi Kofina
Rock mechanics and the estimation of their material properties through field tests are important aspects and challengees in civil and geotechnical engineering. However, this procedure is expensive and difficult to attain, while the machine learning and neural network theory provide a computational tool for estimating the material properties with limited data. In this work, an estimation of the Young Modulus and the cohesion of a clayey-originated rock through feed-forward neural networks constructed from in situ data measurements is given. The input values come from the Geological Strength Index (GSI) proposed values of the point load index Is50, the uniaxial compression strength σs, as well as the specific gravity γ of the rock mass. The convergence analysis revealed that the convergence occurs at approximately 2000 epochs, with the largest L2 mean square error norm being no greater than 10−5. In addition, it is demonstrated that augmenting γ results in the estimation of rock that is stiffer and stronger. The aforementioned increase in the specific site may be up to 20% for the stiffness and up to 25% for the cohesion. This model, aside from readability and accuracy, offers the convenience of enriching it with more in situ data, thereby enhancing the flexibility of the proposed numerical tool proposed. However, its applicability is limited to the specific data acquired from the particular site, so a more general estimation requires a substantially larger dataset. Finally, the justification of the proposed model has been carried out based on suggestions from the literature for common values of clayey-oriented rock, which is fairly disintegrated as seen in the field.
{"title":"An Estimation of Clayey-Oriented Rock Mass Material Properties, Sited in Koropi, Athens, Greece, through Feed-Forward Neural Networks","authors":"Ambrosios-Antonios Savvides, Andreas A. Antoniou, Leonidas Papadopoulos, Anastasia Monia, Kalliopi Kofina","doi":"10.3390/geotechnics3040052","DOIUrl":"https://doi.org/10.3390/geotechnics3040052","url":null,"abstract":"Rock mechanics and the estimation of their material properties through field tests are important aspects and challengees in civil and geotechnical engineering. However, this procedure is expensive and difficult to attain, while the machine learning and neural network theory provide a computational tool for estimating the material properties with limited data. In this work, an estimation of the Young Modulus and the cohesion of a clayey-originated rock through feed-forward neural networks constructed from in situ data measurements is given. The input values come from the Geological Strength Index (GSI) proposed values of the point load index Is50, the uniaxial compression strength σs, as well as the specific gravity γ of the rock mass. The convergence analysis revealed that the convergence occurs at approximately 2000 epochs, with the largest L2 mean square error norm being no greater than 10−5. In addition, it is demonstrated that augmenting γ results in the estimation of rock that is stiffer and stronger. The aforementioned increase in the specific site may be up to 20% for the stiffness and up to 25% for the cohesion. This model, aside from readability and accuracy, offers the convenience of enriching it with more in situ data, thereby enhancing the flexibility of the proposed numerical tool proposed. However, its applicability is limited to the specific data acquired from the particular site, so a more general estimation requires a substantially larger dataset. Finally, the justification of the proposed model has been carried out based on suggestions from the literature for common values of clayey-oriented rock, which is fairly disintegrated as seen in the field.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"69 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135925983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-21DOI: 10.3390/geotechnics3030051
Mate Janos Vamos, Janos Szendefy
Rutting is one of the most common types of distress in flexible pavement structures. There are two fundamental methods of designing pavement structures: conventional empirical methods and analytical approaches. Many analytical and empirical design procedures assume that rutting is mostly of asphalt origin and can be reduced by limiting the vertical deformation or stress at the top of the subgrade, but they do not quantify the rutting depth itself. Mechanistic–empirical models to predict the permanent deformations of unbound pavement layers have been well investigated and are rather common in North America; however, they are not widely utilized in the rest of the world. To date, there is no generally accepted, widely recognized, and documented procedure for calculating permanent deformations and thus for determining the rutting depth in flexible pavement courses originating from the unbound granular layers. This paper presents a layered calculation method with which the deformation of soil layers (base, subbase, and subgrade courses) under flexible pavements due to repeated traffic load can be determined. In the first step, the cyclic strain amplitude is calculated using a nonlinear material model that is based on particle size distribution parameters (d50 and CU) and dependent on the mean normal stress, relative density, and actual strain level. In the second step, the HCA (High Cycle Accumulation) model is used to calculate the residual settlement of each sublayer as a function of the number of cycles. It is shown that the developed model is suitable for describing different types of subgrades and pavement cross-sections. It is also demonstrated with finite element calculations that the developed model describes both the elastic and plastic strains sufficiently accurately. The developed model can predict the settlement and rutting of pavement structures with sufficient accuracy based on easily available particle size distribution parameters without the need for complex laboratory and finite element tests.
{"title":"Calculation Method for Traffic Load-Induced Permanent Deformation in Soils under Flexible Pavements","authors":"Mate Janos Vamos, Janos Szendefy","doi":"10.3390/geotechnics3030051","DOIUrl":"https://doi.org/10.3390/geotechnics3030051","url":null,"abstract":"Rutting is one of the most common types of distress in flexible pavement structures. There are two fundamental methods of designing pavement structures: conventional empirical methods and analytical approaches. Many analytical and empirical design procedures assume that rutting is mostly of asphalt origin and can be reduced by limiting the vertical deformation or stress at the top of the subgrade, but they do not quantify the rutting depth itself. Mechanistic–empirical models to predict the permanent deformations of unbound pavement layers have been well investigated and are rather common in North America; however, they are not widely utilized in the rest of the world. To date, there is no generally accepted, widely recognized, and documented procedure for calculating permanent deformations and thus for determining the rutting depth in flexible pavement courses originating from the unbound granular layers. This paper presents a layered calculation method with which the deformation of soil layers (base, subbase, and subgrade courses) under flexible pavements due to repeated traffic load can be determined. In the first step, the cyclic strain amplitude is calculated using a nonlinear material model that is based on particle size distribution parameters (d50 and CU) and dependent on the mean normal stress, relative density, and actual strain level. In the second step, the HCA (High Cycle Accumulation) model is used to calculate the residual settlement of each sublayer as a function of the number of cycles. It is shown that the developed model is suitable for describing different types of subgrades and pavement cross-sections. It is also demonstrated with finite element calculations that the developed model describes both the elastic and plastic strains sufficiently accurately. The developed model can predict the settlement and rutting of pavement structures with sufficient accuracy based on easily available particle size distribution parameters without the need for complex laboratory and finite element tests.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136236444","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-16DOI: 10.3390/geotechnics3030050
Nick Hudyma, B. Burçin Avar, Bhaskar Chittoori
The indirect tension test is an important laboratory test for rock characterization. The presence of rock fabric, such as schistosity, complicates the assessment of test results. One hundred and forty-five indirect tension tests were conducted on mica schist specimens to investigate the effect of schistosity orientation on failure mode and tensile strength. Tensile strength results did not provide a clear relationship between schistosity orientation and tensile strength, so the failure patterns were investigated. A new naming scheme for failure modes was developed, incorporating fracture patterns observed in the specimen faces and edges. The Single Mode failure group specimens had only one failure pattern that appeared on both specimen faces, either axial failure (seventy-three specimens), schistosity failure (six specimens), or out-of-plane failure (seven specimens). The Mixed Mode failure group had thirty-two specimens that exhibited one failure pattern on one face and another on the other. The Hybrid Mode failure group had twenty-seven specimens with multiple failure patterns on both specimen faces. It was noted that Mixed Mode and Hybrid Mode specimens with components of axial failure had higher indirect tensile strengths than specimens without elements of axial failures. Statistical analyses of the tensile strength data using Levene’s Test for equal variances and two-sample t-tests showed no statistical difference between the Mixed Mode and Hybrid Mode failure groups. However, there was a statistical difference between the tensile strengths of the Single Mode axial failure specimens and the combined Mixed Mode and Hybrid Mode failure groups. These results clearly emphasize that indirect tensile strength should be assessed using schistosity orientation and failure mode.
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