Pub Date : 2023-04-28DOI: 10.3390/geotechnics3020015
Lila Mouali, G. Veylon, D. Dias, L. Peyras, C. Carvajal, J. Duriez, Eric Antoinet
This paper presents a laboratory investigation of the strain-dependent cyclic properties of a compacted tropical residual soil as measured in a resonant column and cyclic triaxial testing program. The mechanical properties were evaluated with respect to cyclic shear strain amplitude, initial void ratio, and confining pressure. It was shown that the existing models for the prediction of shear modulus reduction and damping ratio curves were not pertinent in the case of the compacted residual soil studied. Empirical equations were developed for the small-strain shear modulus and the normalized shear modulus, damping ratio, and pore water pressure ratio curves for void ratios between e = 1.00 and e = 1.50 and mean effective pressures of p′ = 50−300 kPa. The comparison of the models to the measured values suggest that the uncertainties associated with each of these models are lower than 20% of the predicted values. The results were established as part of a project for the construction of an embankment dam in the West Indies. However, the methodology as well as the model formulation framework presented in the article can be generalized to other residual soils and applied in all fields of geotechnical engineering.
{"title":"Dynamic Properties of a Compacted Residual Soil from the West Indies","authors":"Lila Mouali, G. Veylon, D. Dias, L. Peyras, C. Carvajal, J. Duriez, Eric Antoinet","doi":"10.3390/geotechnics3020015","DOIUrl":"https://doi.org/10.3390/geotechnics3020015","url":null,"abstract":"This paper presents a laboratory investigation of the strain-dependent cyclic properties of a compacted tropical residual soil as measured in a resonant column and cyclic triaxial testing program. The mechanical properties were evaluated with respect to cyclic shear strain amplitude, initial void ratio, and confining pressure. It was shown that the existing models for the prediction of shear modulus reduction and damping ratio curves were not pertinent in the case of the compacted residual soil studied. Empirical equations were developed for the small-strain shear modulus and the normalized shear modulus, damping ratio, and pore water pressure ratio curves for void ratios between e = 1.00 and e = 1.50 and mean effective pressures of p′ = 50−300 kPa. The comparison of the models to the measured values suggest that the uncertainties associated with each of these models are lower than 20% of the predicted values. The results were established as part of a project for the construction of an embankment dam in the West Indies. However, the methodology as well as the model formulation framework presented in the article can be generalized to other residual soils and applied in all fields of geotechnical engineering.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"25 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78170417","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 : 2023-04-23DOI: 10.3390/geotechnics3020014
L. M. Hernandez, E. Garzón, P. Sánchez-Soto, E. Morales
This research focuses on the potential for microbial treatment to stabilize compacted soils, which are often utilized in earthwork projects. A silt–clay sand was used to describe a particular kind of soil. The suggested remedy makes use of the soil’s naturally occurring urea and Ca2+, as well as microorganisms introduced to the compaction water. Two alternative initial water-content types were examined: those on the dry side and those close to the ideal Proctor conditions. Bacillaceae microorganisms were used to induce microbial CaCO3 precipitation and improve the hydraulic and mechanical properties of the compacted soil. The samples were biotreated and immediately compacted, so that the precipitation of calcium carbonate during the curing process took place in the contact areas between the particles (biocementation) and in the pore space (bioclogging). A set of techniques were used to study the ageing effects, such as the water-retention curve by dew-points psychrometer, mercury porosimetry intrusion, permeability, ultrasonic pulse velocity, resonant column, and unconfined and tensile-compression tests. During the ageing, it was observed that the bacterial activity consumed water for the hydrolysis of urea and other intermediate reactions to precipitate CaCO3. This process resulted in a retraction of the microstructure and a change in the macrostructure. The bioclogging phenomenon was more evident in the soil microstructure, while the biocementation process was easier to observe in the macrostructure. The suction’s effects on the soil stiffness were studied in detail, and a significant increase was detected. Despite these water-content losses, which caused soil stiffening by increasing the suction, it was still feasible to identify the gradual rise in small-strain stiffness throughout incubation. The unconfined and tensile-compression tests showed a similar progressive increase in terms of peak compressive and peak splitting strength during the incubation. These results are of interest when microbiological treatments are applied in soils to produce cementitious materials, with the present investigation demonstrating a complete study of their geotechnical behaviour.
{"title":"Simultaneous Biocementation and Compaction of a Soil to Avoid the Breakage of Cementitious Structures during the Execution of Earthwork Constructions","authors":"L. M. Hernandez, E. Garzón, P. Sánchez-Soto, E. Morales","doi":"10.3390/geotechnics3020014","DOIUrl":"https://doi.org/10.3390/geotechnics3020014","url":null,"abstract":"This research focuses on the potential for microbial treatment to stabilize compacted soils, which are often utilized in earthwork projects. A silt–clay sand was used to describe a particular kind of soil. The suggested remedy makes use of the soil’s naturally occurring urea and Ca2+, as well as microorganisms introduced to the compaction water. Two alternative initial water-content types were examined: those on the dry side and those close to the ideal Proctor conditions. Bacillaceae microorganisms were used to induce microbial CaCO3 precipitation and improve the hydraulic and mechanical properties of the compacted soil. The samples were biotreated and immediately compacted, so that the precipitation of calcium carbonate during the curing process took place in the contact areas between the particles (biocementation) and in the pore space (bioclogging). A set of techniques were used to study the ageing effects, such as the water-retention curve by dew-points psychrometer, mercury porosimetry intrusion, permeability, ultrasonic pulse velocity, resonant column, and unconfined and tensile-compression tests. During the ageing, it was observed that the bacterial activity consumed water for the hydrolysis of urea and other intermediate reactions to precipitate CaCO3. This process resulted in a retraction of the microstructure and a change in the macrostructure. The bioclogging phenomenon was more evident in the soil microstructure, while the biocementation process was easier to observe in the macrostructure. The suction’s effects on the soil stiffness were studied in detail, and a significant increase was detected. Despite these water-content losses, which caused soil stiffening by increasing the suction, it was still feasible to identify the gradual rise in small-strain stiffness throughout incubation. The unconfined and tensile-compression tests showed a similar progressive increase in terms of peak compressive and peak splitting strength during the incubation. These results are of interest when microbiological treatments are applied in soils to produce cementitious materials, with the present investigation demonstrating a complete study of their geotechnical behaviour.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"35 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90566406","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}
K. Wang, Wenjie Tan, Yanxiao Si, Yue Ma, Xiaohui Chen, A. Ding
Rock, soil and many porous-like materials are often fractured or structured media, which can exhibit dual-porosity behaviour. Studies on solute transport in deformable dual-porosity media remain challenging due to the multi-physics coupled effects and the complex interaction between fracture (or macropore) and porous matrix. Though several studies exist on constitutive modelling of coupled behaviour in deformable dual-porosity, the previously developed models are not systematic in thermodynamical frameworks. This paper proposes a Mixture Coupling Theory approach based on nonequilibrium thermodynamics to develop the solute transport model with consideration of hydro-mechanical coupling in dual-porosity media (referred to as the ST-HM model). This paper derives the constitutive equations of fully hydro-mechanical coupled behaviour in dual-porosity media and considers the pore and fracture porosity evolution influenced by both hydro and mechanical fields. Therefore, the governing equations of ST-HM are capable of predicting non-reactive solute transport with a fully hydro-mechanical coupled effect in dual-porosity media. Then, the model was verified against existing models and validated by relevant experimental results. Further, a numerical example shows that the presented model significantly improves the accuracy of the prediction of porosity, fluid pressure, and solute concentration compared with previous models, which ignore the fully hydro-mechanical coupled effects on solute transport.
{"title":"A Mixture Coupling Theory based model for solute transport in deformable dual-porosity media","authors":"K. Wang, Wenjie Tan, Yanxiao Si, Yue Ma, Xiaohui Chen, A. Ding","doi":"10.1680/jenge.22.00029","DOIUrl":"https://doi.org/10.1680/jenge.22.00029","url":null,"abstract":"Rock, soil and many porous-like materials are often fractured or structured media, which can exhibit dual-porosity behaviour. Studies on solute transport in deformable dual-porosity media remain challenging due to the multi-physics coupled effects and the complex interaction between fracture (or macropore) and porous matrix. Though several studies exist on constitutive modelling of coupled behaviour in deformable dual-porosity, the previously developed models are not systematic in thermodynamical frameworks. This paper proposes a Mixture Coupling Theory approach based on nonequilibrium thermodynamics to develop the solute transport model with consideration of hydro-mechanical coupling in dual-porosity media (referred to as the ST-HM model). This paper derives the constitutive equations of fully hydro-mechanical coupled behaviour in dual-porosity media and considers the pore and fracture porosity evolution influenced by both hydro and mechanical fields. Therefore, the governing equations of ST-HM are capable of predicting non-reactive solute transport with a fully hydro-mechanical coupled effect in dual-porosity media. Then, the model was verified against existing models and validated by relevant experimental results. Further, a numerical example shows that the presented model significantly improves the accuracy of the prediction of porosity, fluid pressure, and solute concentration compared with previous models, which ignore the fully hydro-mechanical coupled effects on solute transport.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43858921","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 : 2023-04-16DOI: 10.3390/geotechnics3020013
I. Akram, S. Azam
The geotechnical behavior of cohesionless soils is governed by field conditions. Such soils exist in two distinct forms, namely: disintegrated, such as fresh sediments under no overburden and/or no suction, and intact, such as old deposits with overburden and/or suction. The main contribution of this research was the successful capture of field conditions in laboratory samples, and the determination of shear strength under saturated and dried states. Results indicated that disintegrated samples possess identical soil behavior under both saturation states. Shear stiffness and peak shear increased with increasing normal stress, and no clear failure peaks were observed, similar to loose soils. Both samples showed an initial contraction followed by dilation at low normal stresses and mostly contraction at high normal stresses. Apparent cohesion was non-existent, and the friction angle measured 44.5° in the saturated state and 48° in the dried state. The intact sample exhibited behavior similar to the disintegrated sample when saturated. Under the dried state, clear failure peaks followed by residual shear were observed, similar to dense soils. Soil response was primarily dilative at low normal stresses and largely contractive under high normal stresses. Apparent cohesion was zero, and friction angle was 42° in the saturated state and changed to 91 kPa and 36°, respectively, in the dried state. Finally, structural cohesion increased with normal stress, and the friction angle due to suction was between 0.05° and 0.02°.
{"title":"Effect of Sample Preparation on Saturated and Unsaturated Shear Strength of Cohesionless Soils","authors":"I. Akram, S. Azam","doi":"10.3390/geotechnics3020013","DOIUrl":"https://doi.org/10.3390/geotechnics3020013","url":null,"abstract":"The geotechnical behavior of cohesionless soils is governed by field conditions. Such soils exist in two distinct forms, namely: disintegrated, such as fresh sediments under no overburden and/or no suction, and intact, such as old deposits with overburden and/or suction. The main contribution of this research was the successful capture of field conditions in laboratory samples, and the determination of shear strength under saturated and dried states. Results indicated that disintegrated samples possess identical soil behavior under both saturation states. Shear stiffness and peak shear increased with increasing normal stress, and no clear failure peaks were observed, similar to loose soils. Both samples showed an initial contraction followed by dilation at low normal stresses and mostly contraction at high normal stresses. Apparent cohesion was non-existent, and the friction angle measured 44.5° in the saturated state and 48° in the dried state. The intact sample exhibited behavior similar to the disintegrated sample when saturated. Under the dried state, clear failure peaks followed by residual shear were observed, similar to dense soils. Soil response was primarily dilative at low normal stresses and largely contractive under high normal stresses. Apparent cohesion was zero, and friction angle was 42° in the saturated state and changed to 91 kPa and 36°, respectively, in the dried state. Finally, structural cohesion increased with normal stress, and the friction angle due to suction was between 0.05° and 0.02°.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"1 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83381832","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 : 2023-04-13DOI: 10.3390/geotechnics3020012
H. Nowamooz
This work investigates the equilibrium stage of the crack propagation of a fine-grained soil after several drying and wetting cycles (shrinkage and swelling hysteresis). This stage is found to be crucial in practical engineering since the soil continues to show its irreversible hydraulic settlement, which is a potential risk for some severe structural damages. The shrinkage area and the shrinkage crack area were determined by using the image processing method. For the cyclic experimental investigations, the shrinkage cracks were followed during six months of successive wetting and drying cycles for two samples (with two different initial water contents). These long-term tests were completed by some short term single drying path tests performed on samples prepared at different initial states. The results showed the existence of a unique equilibrium stage at the end of the wetting and drying cycles for the two studied samples. The equilibrated soil subsidence was separated into two parts: the reversible settlement of the equilibrium stage and the irreversible settlements cumulated during successive wetting and drying cycles. At the equilibrium stage, the reversible deformation was 5.9% and the irreversible deformation was 3.8%. A simplified theoretical approach was also used to predict the cracking equilibrium stage and its soil subsidence. The fitted parameters of the theoretical approach for each cycle were stabilized to confirm the existence of this equilibrium stage.
{"title":"Equilibrium Stage of Soil Cracking and Subsidence after Several Wetting and Drying Cycles","authors":"H. Nowamooz","doi":"10.3390/geotechnics3020012","DOIUrl":"https://doi.org/10.3390/geotechnics3020012","url":null,"abstract":"This work investigates the equilibrium stage of the crack propagation of a fine-grained soil after several drying and wetting cycles (shrinkage and swelling hysteresis). This stage is found to be crucial in practical engineering since the soil continues to show its irreversible hydraulic settlement, which is a potential risk for some severe structural damages. The shrinkage area and the shrinkage crack area were determined by using the image processing method. For the cyclic experimental investigations, the shrinkage cracks were followed during six months of successive wetting and drying cycles for two samples (with two different initial water contents). These long-term tests were completed by some short term single drying path tests performed on samples prepared at different initial states. The results showed the existence of a unique equilibrium stage at the end of the wetting and drying cycles for the two studied samples. The equilibrated soil subsidence was separated into two parts: the reversible settlement of the equilibrium stage and the irreversible settlements cumulated during successive wetting and drying cycles. At the equilibrium stage, the reversible deformation was 5.9% and the irreversible deformation was 3.8%. A simplified theoretical approach was also used to predict the cracking equilibrium stage and its soil subsidence. The fitted parameters of the theoretical approach for each cycle were stabilized to confirm the existence of this equilibrium stage.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"118 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79395742","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}
The present study aims at perspective utilization of two wastes, bauxite residue (BR)-an extremely alkaline material and phosphogyspum (PG)-a highly acidic substance, of entirely different in nature. Development of alkali activated mortar targeting pavement applications has been explored. As BR and PG alone proved to be ineffectual in developing geopolymer/alkali activated mortar because of undesirably low compressive strength, the challenge lies in synthesis of alkali activated mortar envisioning high strength using the combination of these wastes. PG in proportions of 10, 20, 30, 40 and 50%, NaOH molarity of 8, 10, 12, and 14, and Na2SiO3/NaOH ratio of 0.5, 1.0, 1.5, 2.0 and 2.5 are chosen as variable parameters to develop the mortar. From the comprehensive experimental results, 30% of PG, 12 M NaOH and Na2SiO3/NaOH ratio of 1.5 are found as optimum parameters to synthesize the mortar. It is demonstrated that the mortar made at 70:30 combinations of BR and PG exhibits superior compressive strength of 31.24 MPa, minimum abrasion loss of 1.52 mm, and water absorption of <7%, apart from constraining leaching of potentially toxic elements. On account of mechanical, durability and environmental performance, the present study recommends the above combination as ideally suitable material in pavement applications.
{"title":"Synthesis of alkali activated mortar using phosphogypsum neutralized bauxite residue","authors":"","doi":"10.1680/jenge.22.00104","DOIUrl":"https://doi.org/10.1680/jenge.22.00104","url":null,"abstract":"The present study aims at perspective utilization of two wastes, bauxite residue (BR)-an extremely alkaline material and phosphogyspum (PG)-a highly acidic substance, of entirely different in nature. Development of alkali activated mortar targeting pavement applications has been explored. As BR and PG alone proved to be ineffectual in developing geopolymer/alkali activated mortar because of undesirably low compressive strength, the challenge lies in synthesis of alkali activated mortar envisioning high strength using the combination of these wastes. PG in proportions of 10, 20, 30, 40 and 50%, NaOH molarity of 8, 10, 12, and 14, and Na2SiO3/NaOH ratio of 0.5, 1.0, 1.5, 2.0 and 2.5 are chosen as variable parameters to develop the mortar. From the comprehensive experimental results, 30% of PG, 12 M NaOH and Na2SiO3/NaOH ratio of 1.5 are found as optimum parameters to synthesize the mortar. It is demonstrated that the mortar made at 70:30 combinations of BR and PG exhibits superior compressive strength of 31.24 MPa, minimum abrasion loss of 1.52 mm, and water absorption of <7%, apart from constraining leaching of potentially toxic elements. On account of mechanical, durability and environmental performance, the present study recommends the above combination as ideally suitable material in pavement applications.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"1 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41325910","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 : 2023-04-11DOI: 10.3390/geotechnics3020011
N. Bandara, H. Hettiarachchi, E. Jensen, T. Binoy, R. Perera
Remove-and-replace with suitable material has been the primary solution used for improving subgrades in Michigan, USA, when weak subgrades are encountered in road construction. Considering the large extent of silty and clayey soils found in southeastern Michigan, where much of the population and the roads are located within the state, the earthwork associated with this solution is massive and expensive. The use of cement kiln dust (CKD) or lime kiln dust (LKD) as a subgrade stabilizer can be a cost-effective solution if there is sufficient evidence to prove that such stabilization is suitable for the soils and the climate in southeastern Michigan. This became the subject of a field and laboratory investigation carried out in Michigan and sponsored by the Michigan Department of Transportation. The findings from the laboratory portion of this research (which were published in a separate manuscript) proved CKD’s suitability for long-term stabilization and LKD’s capacity for being a stabilizer for short-term modifications of clayey soils found in southeastern Michigan. This study covers the field testing portion of this investigation. Two CKD-stabilized and another two LKD-stabilized subgrades, which were already in use for 4–6 years, were tested for strength, using dynamic cone penetration (DCP) tests. The California bearing ratios estimated from the DCP tests showed that the CKD-stabilized and LKD-stabilized subgrades could offer strength gains as high as 200–515% and 149–257% compared to in situ soils, respectively, even after 4–6 years in use.
{"title":"Using Kiln Dust to Improve Weak Subgrades for Pavement Construction: A Field Verification in Michigan, USA","authors":"N. Bandara, H. Hettiarachchi, E. Jensen, T. Binoy, R. Perera","doi":"10.3390/geotechnics3020011","DOIUrl":"https://doi.org/10.3390/geotechnics3020011","url":null,"abstract":"Remove-and-replace with suitable material has been the primary solution used for improving subgrades in Michigan, USA, when weak subgrades are encountered in road construction. Considering the large extent of silty and clayey soils found in southeastern Michigan, where much of the population and the roads are located within the state, the earthwork associated with this solution is massive and expensive. The use of cement kiln dust (CKD) or lime kiln dust (LKD) as a subgrade stabilizer can be a cost-effective solution if there is sufficient evidence to prove that such stabilization is suitable for the soils and the climate in southeastern Michigan. This became the subject of a field and laboratory investigation carried out in Michigan and sponsored by the Michigan Department of Transportation. The findings from the laboratory portion of this research (which were published in a separate manuscript) proved CKD’s suitability for long-term stabilization and LKD’s capacity for being a stabilizer for short-term modifications of clayey soils found in southeastern Michigan. This study covers the field testing portion of this investigation. Two CKD-stabilized and another two LKD-stabilized subgrades, which were already in use for 4–6 years, were tested for strength, using dynamic cone penetration (DCP) tests. The California bearing ratios estimated from the DCP tests showed that the CKD-stabilized and LKD-stabilized subgrades could offer strength gains as high as 200–515% and 149–257% compared to in situ soils, respectively, even after 4–6 years in use.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"99 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79298070","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 : 2023-04-06DOI: 10.3390/geotechnics3020010
Mani Axel, Xi‐An Li, Feng Wen, Ming-Xiao An
In this study, cement was used as a component to provide a stabilizing effect in order to evaluate the hardness and stability of loess soil. To evaluate the strength properties of loess soil reinforced with cement, samples with four distinct cement concentrations (3%, 5%, 7%, and 9%) and three distinct curing durations (7, 14, and 28 days) were generated. During a series of tests, the flexural strength, direct shear strength, indirect tensile strength, and unconfined compressive strength were determined. An appropriate cement dosage was found, in addition to a durability index that could be used to quantify the effect of water absorption investigations on cement-stabilized loess. Both of these discoveries were made simultaneously. Scanning electron microscopy (SEM) and energy dispersive X-ray fluorescence spectrometry (XRF) examinations were carried out so that the fundamental mechanics of the materials could be comprehended. The results show that the cohesion of cement-stabilized loess is much more sensitive to structure than the friction angle of the material. The increase in shear strength after remoulding is due to cohesion. The SEM study showed that the cement interacted with the loess particles to produce a thick cement network that successfully covered the voids and boosted the mixture’s strength parameters. The 28-days UCS for the samples containing 7% cement was the greatest, at 3.5 MPa, while the UCS for those containing 9% cement was 4.78 MPa. The highest flexural tensile strength of 1.98 N/mm2 was determined after 28 days. The tensile strength after 7 days in samples containing 3%, 5%, 7%, and 9% cement reached a maximum force of 0.15 MPa, 0.23 MPa, 0.27 MPa, and 0.37 MPa, respectively, and increased with each passing day. To achieve the desired level of strength, it is necessary to adjust the proportion of cement. In addition, as the curing period progressed, we observed an increase in the resistance and stiffness of the cement-stabilized loess due to the interactions that take place between the structure and the mineral composition. It is believed that this event was caused by naturally occurring cementation. As a consequence of this reaction, the production of new cementitious materials takes place. The cation exchange that causes the hydration and pozzolanic reaction that leads to the creation of aggregates and interparticle flocculation is responsible for their production. These findings suggest that cement may be utilised as a simple and effective method of loess stabilization, ultimately resulting in improved performance of the loess. Therefore, this study revealed that cement may considerably enhance the microstructure and strength parameters of loess. This research provides important information on cement-stabilized loess that has ramifications for geotechnical investigation, construction, research, and testing to achieve a successful project.
{"title":"Microstructure and Strength Parameters of Cement-Stabilized Loess","authors":"Mani Axel, Xi‐An Li, Feng Wen, Ming-Xiao An","doi":"10.3390/geotechnics3020010","DOIUrl":"https://doi.org/10.3390/geotechnics3020010","url":null,"abstract":"In this study, cement was used as a component to provide a stabilizing effect in order to evaluate the hardness and stability of loess soil. To evaluate the strength properties of loess soil reinforced with cement, samples with four distinct cement concentrations (3%, 5%, 7%, and 9%) and three distinct curing durations (7, 14, and 28 days) were generated. During a series of tests, the flexural strength, direct shear strength, indirect tensile strength, and unconfined compressive strength were determined. An appropriate cement dosage was found, in addition to a durability index that could be used to quantify the effect of water absorption investigations on cement-stabilized loess. Both of these discoveries were made simultaneously. Scanning electron microscopy (SEM) and energy dispersive X-ray fluorescence spectrometry (XRF) examinations were carried out so that the fundamental mechanics of the materials could be comprehended. The results show that the cohesion of cement-stabilized loess is much more sensitive to structure than the friction angle of the material. The increase in shear strength after remoulding is due to cohesion. The SEM study showed that the cement interacted with the loess particles to produce a thick cement network that successfully covered the voids and boosted the mixture’s strength parameters. The 28-days UCS for the samples containing 7% cement was the greatest, at 3.5 MPa, while the UCS for those containing 9% cement was 4.78 MPa. The highest flexural tensile strength of 1.98 N/mm2 was determined after 28 days. The tensile strength after 7 days in samples containing 3%, 5%, 7%, and 9% cement reached a maximum force of 0.15 MPa, 0.23 MPa, 0.27 MPa, and 0.37 MPa, respectively, and increased with each passing day. To achieve the desired level of strength, it is necessary to adjust the proportion of cement. In addition, as the curing period progressed, we observed an increase in the resistance and stiffness of the cement-stabilized loess due to the interactions that take place between the structure and the mineral composition. It is believed that this event was caused by naturally occurring cementation. As a consequence of this reaction, the production of new cementitious materials takes place. The cation exchange that causes the hydration and pozzolanic reaction that leads to the creation of aggregates and interparticle flocculation is responsible for their production. These findings suggest that cement may be utilised as a simple and effective method of loess stabilization, ultimately resulting in improved performance of the loess. Therefore, this study revealed that cement may considerably enhance the microstructure and strength parameters of loess. This research provides important information on cement-stabilized loess that has ramifications for geotechnical investigation, construction, research, and testing to achieve a successful project.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"16 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79703346","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}
This work examines the study of engineering properties and leachate characteristics of ground granulated blast furnace slag (GGBS) blended with laterite soil-bentonite mixtures as a bottom landfill liner. In this study, laterite soil is referred to as non-expansive and non-plastic clay; on the contrary bentonite is highly expansive and high plastic clay. Laboratory experiments were performed to quantify the effect of GGBS-laterite soil-bentonite mixtures on the liquid limit (LL), free swell index (FSI), compaction characteristics, unconfined compressive strength (UCS), hydraulic conductivity (k), and leachate tests. As GGBS percentage in the mix blend increases, the LL, FSI, optimum moisture content, k determined with deionized water/diesel oil contaminants and leachate concentration decreases, whereas maximum dry densities and UCS value increases. Furthermore, X-ray diffraction analysis and energy dispersive X-ray spectrometer was performed on UCS samples to determine the evidence of hydration reaction in mix blends at 0, 14, and 28 days curing period. The test results revealed that an increase in Ca: Si ratio and a decrease in Al: Ca ratios, augmented the UCS enhancement during the curing period. Consequently, 20% GGBS combined with laterite soil-bentonite mixes proves to be the ideal material for landfill bottom liners in waste containment systems.
{"title":"Assessment of engineering properties on GGBS mixtures as a bottom liner in landfills","authors":"Manikanta Devarangadi, U. M","doi":"10.1680/jenge.22.00166","DOIUrl":"https://doi.org/10.1680/jenge.22.00166","url":null,"abstract":"This work examines the study of engineering properties and leachate characteristics of ground granulated blast furnace slag (GGBS) blended with laterite soil-bentonite mixtures as a bottom landfill liner. In this study, laterite soil is referred to as non-expansive and non-plastic clay; on the contrary bentonite is highly expansive and high plastic clay. Laboratory experiments were performed to quantify the effect of GGBS-laterite soil-bentonite mixtures on the liquid limit (LL), free swell index (FSI), compaction characteristics, unconfined compressive strength (UCS), hydraulic conductivity (k), and leachate tests. As GGBS percentage in the mix blend increases, the LL, FSI, optimum moisture content, k determined with deionized water/diesel oil contaminants and leachate concentration decreases, whereas maximum dry densities and UCS value increases. Furthermore, X-ray diffraction analysis and energy dispersive X-ray spectrometer was performed on UCS samples to determine the evidence of hydration reaction in mix blends at 0, 14, and 28 days curing period. The test results revealed that an increase in Ca: Si ratio and a decrease in Al: Ca ratios, augmented the UCS enhancement during the curing period. Consequently, 20% GGBS combined with laterite soil-bentonite mixes proves to be the ideal material for landfill bottom liners in waste containment systems.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44452900","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}
The usage of various polymers as an alternative in ground improvement problems is steadily gaining popularity. However, certain aspects of the usage of polymers are still not properly addressed. In this paper, an experimental program has been undertaken to study the influence of various polymer contents on the shear wave velocities in granular soils. Different polymer concentrations are mixed with a uniform sand to obtain various concentrations. Resonant column tests are carried out under three different mean effective stresses considering various densities. The results suggest a significant influence of polymer under low stress values due to the coating that reduces normal contact forces between sand grains. The influence of the coating is further seen to decrease since under higher stresses- the coatings are significantly damaged, leading to increase in the stiffness of the specimens the values of which are closer to that measured for the pure sand.
{"title":"The influence of polymer content on the shear wave velocities in fine sand","authors":"D. Sarkar, W. Lieske, M. Goudarzy, T. Wichtmann","doi":"10.1680/jenge.23.00017","DOIUrl":"https://doi.org/10.1680/jenge.23.00017","url":null,"abstract":"The usage of various polymers as an alternative in ground improvement problems is steadily gaining popularity. However, certain aspects of the usage of polymers are still not properly addressed. In this paper, an experimental program has been undertaken to study the influence of various polymer contents on the shear wave velocities in granular soils. Different polymer concentrations are mixed with a uniform sand to obtain various concentrations. Resonant column tests are carried out under three different mean effective stresses considering various densities. The results suggest a significant influence of polymer under low stress values due to the coating that reduces normal contact forces between sand grains. The influence of the coating is further seen to decrease since under higher stresses- the coatings are significantly damaged, leading to increase in the stiffness of the specimens the values of which are closer to that measured for the pure sand.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43526040","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}
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