Pub Date : 2023-10-30DOI: 10.3390/geotechnics3040062
Mohamed Soliman, Roberto Cudmani
Vehicle restraint systems are vital hardware elements in road safety engineering. The certification process of a vehicle restraint system includes full-scale crash tests, component testing and numerical simulation of these tests. To achieve reliable crash test simulation results, the soil–post interaction must be modelled to capture the behaviour realistically. There is no standardised approach for modelling the soil–post interaction in the praxis. In this study, the finite element method is utilised to investigate the soil–post response under quasi-static and dynamic impact loading. Two different modelling techniques are applied for this purpose. The first technique is the finite element continuum method, with the soil modelled using the advanced hypoplastic constitutive relation and calibrated using laboratory test data. The second technique is a lumped-parameter model, for which a systematic parameters calibration routine using basic soil properties is introduced. The numerical models are validated using a series of full-scale field tests performed by the authors on single posts in standard road shoulder materials. The performance comparison of the investigated modelling techniques shows that the hypoplastic constitutive relation can capture the post behaviour realistically under different loading conditions using the same parameter set. The introduced lumped-parameter model adequately simulates the post behaviour with high computational efficiency, which is very important when simulating several posts. The conducted parametric study elucidates that the soil’s relative density, the post’s embedment length, and the post-section modulus govern the single post’s lateral load-bearing behaviour and energy dissipation capacity.
{"title":"Numerical Modelling and Investigation of the Impact Behaviour of Single Guardrail Posts","authors":"Mohamed Soliman, Roberto Cudmani","doi":"10.3390/geotechnics3040062","DOIUrl":"https://doi.org/10.3390/geotechnics3040062","url":null,"abstract":"Vehicle restraint systems are vital hardware elements in road safety engineering. The certification process of a vehicle restraint system includes full-scale crash tests, component testing and numerical simulation of these tests. To achieve reliable crash test simulation results, the soil–post interaction must be modelled to capture the behaviour realistically. There is no standardised approach for modelling the soil–post interaction in the praxis. In this study, the finite element method is utilised to investigate the soil–post response under quasi-static and dynamic impact loading. Two different modelling techniques are applied for this purpose. The first technique is the finite element continuum method, with the soil modelled using the advanced hypoplastic constitutive relation and calibrated using laboratory test data. The second technique is a lumped-parameter model, for which a systematic parameters calibration routine using basic soil properties is introduced. The numerical models are validated using a series of full-scale field tests performed by the authors on single posts in standard road shoulder materials. The performance comparison of the investigated modelling techniques shows that the hypoplastic constitutive relation can capture the post behaviour realistically under different loading conditions using the same parameter set. The introduced lumped-parameter model adequately simulates the post behaviour with high computational efficiency, which is very important when simulating several posts. The conducted parametric study elucidates that the soil’s relative density, the post’s embedment length, and the post-section modulus govern the single post’s lateral load-bearing behaviour and energy dissipation capacity.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"10 35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136022656","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}
Recycling and reuse of plastic waste in civil projects is one way to reduce its negative impacts on the environment. High-density polyethylene (HDPE) is a highly abundant plastic waste found widely and in high volumes worldwide. Although sand has a relatively high frictional resistance, if its dynamic parameters are improved, it can be used in geotechnical projects that require higher dynamic parameters than those of pure sand. This study aimed to investigate the dynamic properties of sand mixed with crushed HDPE waste and its application to mitigate its negative environmental impacts. Crushed HDPE was added to sand at 0, 4 and 8% by weight. Under three vertical stresses and two shear amplitudes, the dynamic parameters of the mixture, including damping and shear stiffness, were investigated by conducting a large-scale cyclic direct shear test under ten cycles and are discussed. The results showed that with increasing HDPE percentage, the damping ratio rose and the shear stiffness decreased compared with those of pure sand due to the elasticity, deformation, tensile properties and high potential of HDPE for energy absorption. Furthermore, the rise in shear amplitude decreased the dynamic shear stiffness and raised the damping ratio of the mixtures.
{"title":"Dynamic properties of HDPE-sand by large-scale direct shear experiments","authors":"Mahyar Arabani, Masoomeh Khodabakhshi","doi":"10.1680/jenge.22.00021","DOIUrl":"https://doi.org/10.1680/jenge.22.00021","url":null,"abstract":"Recycling and reuse of plastic waste in civil projects is one way to reduce its negative impacts on the environment. High-density polyethylene (HDPE) is a highly abundant plastic waste found widely and in high volumes worldwide. Although sand has a relatively high frictional resistance, if its dynamic parameters are improved, it can be used in geotechnical projects that require higher dynamic parameters than those of pure sand. This study aimed to investigate the dynamic properties of sand mixed with crushed HDPE waste and its application to mitigate its negative environmental impacts. Crushed HDPE was added to sand at 0, 4 and 8% by weight. Under three vertical stresses and two shear amplitudes, the dynamic parameters of the mixture, including damping and shear stiffness, were investigated by conducting a large-scale cyclic direct shear test under ten cycles and are discussed. The results showed that with increasing HDPE percentage, the damping ratio rose and the shear stiffness decreased compared with those of pure sand due to the elasticity, deformation, tensile properties and high potential of HDPE for energy absorption. Furthermore, the rise in shear amplitude decreased the dynamic shear stiffness and raised the damping ratio of the mixtures.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"358 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135513936","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 : 2023-10-20DOI: 10.3390/geotechnics3040061
Anthony Mouyeaux, Claudio Carvajal, François Nicot, Antoine Wautier, Laurent Peyras
Slope instability issues could cause severe damage and endanger the population, especially when dams are concerned. Over the past years, more and more refined numerical approaches have been proposed to evaluate the slope stability. However, a criterion based on the lack of numerical convergence is generally considered to compute the safety factor with this kind of approaches, which may result in a dramatic increase in the overall computation time for the probabilistic assessment of the safety factor (e.g., using Monte Carlo simulations that require the automation of a large number of simulations). This paper proposes an original approach coupling the shear strength reduction technique with the second-order work criterion. This approach is implemented in the open finite element software Cast3M, version 22.0. The relevance and efficiency of the developed approach is illustrated with two case studies: a heuristic slope and an existing earth dam. Safety factors similar to those calculated by classical approaches are obtained, but without pushing the calculation to the point of non-convergence. Among other advantages described in the paper, the proposed approach makes it possible to compute safety factors using a rational and physically based criterion, while facilitating probabilistic calculations.
{"title":"Stability Analysis of Earth Dam Slopes Based on the Second-Order Work Criterion in Finite Element Modeling","authors":"Anthony Mouyeaux, Claudio Carvajal, François Nicot, Antoine Wautier, Laurent Peyras","doi":"10.3390/geotechnics3040061","DOIUrl":"https://doi.org/10.3390/geotechnics3040061","url":null,"abstract":"Slope instability issues could cause severe damage and endanger the population, especially when dams are concerned. Over the past years, more and more refined numerical approaches have been proposed to evaluate the slope stability. However, a criterion based on the lack of numerical convergence is generally considered to compute the safety factor with this kind of approaches, which may result in a dramatic increase in the overall computation time for the probabilistic assessment of the safety factor (e.g., using Monte Carlo simulations that require the automation of a large number of simulations). This paper proposes an original approach coupling the shear strength reduction technique with the second-order work criterion. This approach is implemented in the open finite element software Cast3M, version 22.0. The relevance and efficiency of the developed approach is illustrated with two case studies: a heuristic slope and an existing earth dam. Safety factors similar to those calculated by classical approaches are obtained, but without pushing the calculation to the point of non-convergence. Among other advantages described in the paper, the proposed approach makes it possible to compute safety factors using a rational and physically based criterion, while facilitating probabilistic calculations.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135569205","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 : 2023-10-16DOI: 10.3390/geotechnics3040059
Donald Cameron, Md Rajibul Karim, Tim Johnson, Md Mizanur Rahman
Expansive soils change volume due to changes in moisture content, which results in ground movement. Lightweight shallow-depth structures such as pavements, residential footings, and pipelines can suffer distress as they face additional stresses from the moving ground. The soil reactivity (the ability of soil to expand or contract due to change in moisture content) and the interactions at the soil-atmosphere-vegetation boundary are two of the major contributing factors to the ground movement. The current methodology used in design to account for ground movement is based on limited field and laboratory observations. Aiming at a better understanding of the interaction at the soil-atmosphere-vegetation boundary and its correlation with ground movement, this paper presents results from a field study. The research site was located in a semi-arid climate area and consisted of moderately to highly reactive clay soils. Part of the site was vegetated with mature trees, and part was occupied by grass. The order of 10 s of mm difference was observed in the magnitude of movement across the site owing to site soil variability as well as differences in vegetation. The areas with large trees showed relatively lower ground movement over the study period compared to the area occupied by grass, which was attributed to the microclimate created by the tree canopy and the already established deeper drying of the soil near the trees.
{"title":"Influence of Weather, Soil Variability, and Vegetation on Seasonal Ground Movement: A Field Study","authors":"Donald Cameron, Md Rajibul Karim, Tim Johnson, Md Mizanur Rahman","doi":"10.3390/geotechnics3040059","DOIUrl":"https://doi.org/10.3390/geotechnics3040059","url":null,"abstract":"Expansive soils change volume due to changes in moisture content, which results in ground movement. Lightweight shallow-depth structures such as pavements, residential footings, and pipelines can suffer distress as they face additional stresses from the moving ground. The soil reactivity (the ability of soil to expand or contract due to change in moisture content) and the interactions at the soil-atmosphere-vegetation boundary are two of the major contributing factors to the ground movement. The current methodology used in design to account for ground movement is based on limited field and laboratory observations. Aiming at a better understanding of the interaction at the soil-atmosphere-vegetation boundary and its correlation with ground movement, this paper presents results from a field study. The research site was located in a semi-arid climate area and consisted of moderately to highly reactive clay soils. Part of the site was vegetated with mature trees, and part was occupied by grass. The order of 10 s of mm difference was observed in the magnitude of movement across the site owing to site soil variability as well as differences in vegetation. The areas with large trees showed relatively lower ground movement over the study period compared to the area occupied by grass, which was attributed to the microclimate created by the tree canopy and the already established deeper drying of the soil near the trees.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136114545","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 : 2023-10-16DOI: 10.3390/geotechnics3040060
Ferdinando Totani
To evaluate the importance of the site effects of large structures such as the new Belvedere Bridge (L’Aquila), which crosses a 25 m deep and 100 m valley in the city, one-dimensional and two-dimensional analyses were used to model the seismic response. The results indicate that the valley effects and the geometry of the bridge construction section have a significant influence on ground motions, especially at the points where the natural morphology has been altered by civil works carried out over time. In the presence of vertically propagating shear waves (SVs), the synthetic parameters of seismic motion, such as the maximum ground acceleration (PGA), the amplification factors (AFs), and the elastic acceleration response spectra (Ses), are crucial aspects to identify. The different motions generated between the anchorage points of the bridge foundations, even though they exhibit reduced proportions, and the site effects should be considered in bridge design.
{"title":"Two-Dimensional Seismic Response Analysis to Evaluate the Site Effects of the New Belvedere Bridge (L’Aquila, Central Italy)","authors":"Ferdinando Totani","doi":"10.3390/geotechnics3040060","DOIUrl":"https://doi.org/10.3390/geotechnics3040060","url":null,"abstract":"To evaluate the importance of the site effects of large structures such as the new Belvedere Bridge (L’Aquila), which crosses a 25 m deep and 100 m valley in the city, one-dimensional and two-dimensional analyses were used to model the seismic response. The results indicate that the valley effects and the geometry of the bridge construction section have a significant influence on ground motions, especially at the points where the natural morphology has been altered by civil works carried out over time. In the presence of vertically propagating shear waves (SVs), the synthetic parameters of seismic motion, such as the maximum ground acceleration (PGA), the amplification factors (AFs), and the elastic acceleration response spectra (Ses), are crucial aspects to identify. The different motions generated between the anchorage points of the bridge foundations, even though they exhibit reduced proportions, and the site effects should be considered in bridge design.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"96 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136115573","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 dioxide 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 three-dimensional (3D) analyses and the explicit simulation of heat exchanger pipes, relying instead on two-dimensional 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 the pile per unit length. Conversely, when heating or cooling loads are specified through extracted or injected heat fluxes, the inlet and outlet fluid temperatures, as well as average temperatures at the 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":"A simplified methodology for determining the thermal performance of thermo-active piles","authors":"Ryan Yin Wai Liu, David M G Taborda","doi":"10.1680/jenge.22.00119","DOIUrl":"https://doi.org/10.1680/jenge.22.00119","url":null,"abstract":"Ground source energy systems provide low carbon dioxide 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 three-dimensional (3D) analyses and the explicit simulation of heat exchanger pipes, relying instead on two-dimensional 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 the pile per unit length. Conversely, when heating or cooling loads are specified through extracted or injected heat fluxes, the inlet and outlet fluid temperatures, as well as average temperatures at the 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":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136112369","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 : 2023-10-14DOI: 10.3390/geotechnics3040058
Andreas Wiegel, Andrés A. Peña-Olarte, Roberto Cudmani
Building information modeling (BIM) in the planning and construction of infrastructure projects, such as roads, tunnels, and excavations, requires the generation of comprehensive 3D subsoil models that encompass relevant geological and geotechnical information. Presently, this process relies on the deterministic interpolation of discrete data points obtained from exploratory boreholes and soundings, resulting in a single deterministic prediction. Commonly employed interpolation methods for this purpose include radial basis function and kriging. This contribution introduces probabilistic methods for quantifying prediction uncertainty. The proposed modeling approach is illustrated using simple examples, demonstrating how to use sequential Gaussian and Indicator Simulation techniques to model sedimentary processes such as erosion and lenticular bedding. Subsequently, a site in Munich serves as a case study. The widely used industry foundation classes (IFC) schema allows the integration of the model into the BIM environment. A mapping procedure allows transferring voxel models to the IFC schema. This article discusses the significance of incorporating uncertainty quantification into subsoil modeling and shows its integration into the BIM framework. The proposed approach and its efficient integration with evolving BIM standards and methodologies provides valuable insights for the planning and construction of infrastructure projects.
{"title":"Perspectives of 3D Probabilistic Subsoil Modeling for BIM","authors":"Andreas Wiegel, Andrés A. Peña-Olarte, Roberto Cudmani","doi":"10.3390/geotechnics3040058","DOIUrl":"https://doi.org/10.3390/geotechnics3040058","url":null,"abstract":"Building information modeling (BIM) in the planning and construction of infrastructure projects, such as roads, tunnels, and excavations, requires the generation of comprehensive 3D subsoil models that encompass relevant geological and geotechnical information. Presently, this process relies on the deterministic interpolation of discrete data points obtained from exploratory boreholes and soundings, resulting in a single deterministic prediction. Commonly employed interpolation methods for this purpose include radial basis function and kriging. This contribution introduces probabilistic methods for quantifying prediction uncertainty. The proposed modeling approach is illustrated using simple examples, demonstrating how to use sequential Gaussian and Indicator Simulation techniques to model sedimentary processes such as erosion and lenticular bedding. Subsequently, a site in Munich serves as a case study. The widely used industry foundation classes (IFC) schema allows the integration of the model into the BIM environment. A mapping procedure allows transferring voxel models to the IFC schema. This article discusses the significance of incorporating uncertainty quantification into subsoil modeling and shows its integration into the BIM framework. The proposed approach and its efficient integration with evolving BIM standards and methodologies provides valuable insights for the planning and construction of infrastructure projects.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135766399","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 growing demand for low-cost sorbents, which guarantee eco-efficiency in removing contaminants, has led to numerous studies in recent decades. In this sense, sorbents derived from organic residues have shown promising options; however, the organic fraction of municipal solid waste (OFMSW) has received little attention to date. This study compares the zinc (Zn) sorption performance of a traditional sorbent (peat) to that of materials derived from OFMSW (compost and biochar). According to Langmuir model, biochar showed the highest sorption capacity (53.494 mg g −1 ), followed by compost (37.569 mg g −1 ) and peat (5.842 mg g −1 ). Although the maximum sorption capacities adjusted by linear and non-linear regressions were close, the values were relevant only when they reached the saturation plateau. The cost estimate of the studied sorbents validated their economic viability compared to commercially available ones. The findings provide a theoretical basis for a better understanding of sorption experiments, from the choice of initial concentrations to the isothermal modelling of the results, for comparative evaluations of potential sorbents for the remediation of soils and waters contaminated with potentially toxic metals, such as Zn.
{"title":"Sorption and economic viability of peat, compost, and biochar for Zn-contaminated site remediation","authors":"Jacqueline Zanin Lima, Eduardo Anselmo Ferreira da Silva, Valéria Guimarães Silvestre Rodrigues","doi":"10.1680/jenge.22.00046","DOIUrl":"https://doi.org/10.1680/jenge.22.00046","url":null,"abstract":"The growing demand for low-cost sorbents, which guarantee eco-efficiency in removing contaminants, has led to numerous studies in recent decades. In this sense, sorbents derived from organic residues have shown promising options; however, the organic fraction of municipal solid waste (OFMSW) has received little attention to date. This study compares the zinc (Zn) sorption performance of a traditional sorbent (peat) to that of materials derived from OFMSW (compost and biochar). According to Langmuir model, biochar showed the highest sorption capacity (53.494 mg g −1 ), followed by compost (37.569 mg g −1 ) and peat (5.842 mg g −1 ). Although the maximum sorption capacities adjusted by linear and non-linear regressions were close, the values were relevant only when they reached the saturation plateau. The cost estimate of the studied sorbents validated their economic viability compared to commercially available ones. The findings provide a theoretical basis for a better understanding of sorption experiments, from the choice of initial concentrations to the isothermal modelling of the results, for comparative evaluations of potential sorbents for the remediation of soils and waters contaminated with potentially toxic metals, such as Zn.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135858188","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 : 2023-10-12DOI: 10.3390/geotechnics3040057
Christine Ann Spencer, Henrik Sass, Leon van Paassen
The cementation medium for ureolytic microbially induced calcium carbonate precipitation (MICP) typically consists of urea and a calcium source. While some studies have augmented this basic medium, the effects of adding substrates such as ammonium chloride are unclear. The studies detailed in this paper sought to quantify the effect of the ammonium chloride augmentation of cementation medium (CM) on the process of MICP. An aqueous MICP study was initially carried out to study the effects of adding ammonium chloride to the urea–calcium cementation medium. This batch test also explored the effect of varying the concentration of calcium chloride dihydrate (calcium source) in the CM. A subsequent sand column study was undertaken, whereby multiple treatments of CM were injected over several days to produce a biocement. Six columns were prepared using F65 sand bioaugmented with Sporosarcina pasteurii, half of which were injected with the basic medium only and half with the augmented medium for treatment two onwards. Effluent displaced from columns was tested using ion chromatography and Nesslerisation to determine the calcium and ammonium ion concentrations, respectively, and hence the treatment efficiency. Conductivity and pH testing of effluent gave insights into the bacterial urease activity. The addition of 0.187 M ammonium chloride to the CM resulted in approximately 100% chemical conversion efficiency within columns, based on calcium ion measurements, compared to only 57% and 33% efficiency for treatments three and four, respectively, when using the urea–calcium medium. Columns treated with the CM containing ammonium chloride had unconfined compressive strengths which were 1.8 times higher on average than columns treated with the urea–calcium medium only.
{"title":"Increased Microbially Induced Calcium Carbonate Precipitation (MICP) Efficiency in Multiple Treatment Sand Biocementation Processes by Augmentation of Cementation Medium with Ammonium Chloride","authors":"Christine Ann Spencer, Henrik Sass, Leon van Paassen","doi":"10.3390/geotechnics3040057","DOIUrl":"https://doi.org/10.3390/geotechnics3040057","url":null,"abstract":"The cementation medium for ureolytic microbially induced calcium carbonate precipitation (MICP) typically consists of urea and a calcium source. While some studies have augmented this basic medium, the effects of adding substrates such as ammonium chloride are unclear. The studies detailed in this paper sought to quantify the effect of the ammonium chloride augmentation of cementation medium (CM) on the process of MICP. An aqueous MICP study was initially carried out to study the effects of adding ammonium chloride to the urea–calcium cementation medium. This batch test also explored the effect of varying the concentration of calcium chloride dihydrate (calcium source) in the CM. A subsequent sand column study was undertaken, whereby multiple treatments of CM were injected over several days to produce a biocement. Six columns were prepared using F65 sand bioaugmented with Sporosarcina pasteurii, half of which were injected with the basic medium only and half with the augmented medium for treatment two onwards. Effluent displaced from columns was tested using ion chromatography and Nesslerisation to determine the calcium and ammonium ion concentrations, respectively, and hence the treatment efficiency. Conductivity and pH testing of effluent gave insights into the bacterial urease activity. The addition of 0.187 M ammonium chloride to the CM resulted in approximately 100% chemical conversion efficiency within columns, based on calcium ion measurements, compared to only 57% and 33% efficiency for treatments three and four, respectively, when using the urea–calcium medium. Columns treated with the CM containing ammonium chloride had unconfined compressive strengths which were 1.8 times higher on average than columns treated with the urea–calcium medium only.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136014222","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 : 2023-10-08DOI: 10.3390/geotechnics3040056
Carmine P. Polito
One common method of estimating emax and emin for mixtures of sand and silt requires that the values of several empirical constants be determined. These empirical constants are the filling coefficients, a, and embedment coefficients, b, which can be determined either via lab testing or correlations. The study reported here developed simple correlations for estimating the filling and embedment coefficients using readily obtained laboratory data. These models were found to be excellent in producing filling and embedment coefficients that accurately predicted values of the index void ratios for sand and silt mixtures, with most R2 values being 0.94 or greater.
{"title":"Correlations for Estimating Coefficients for the Prediction of Maximum and Minimum Index Void Ratios for Mixtures of Sand and Non-Plastic Silt","authors":"Carmine P. Polito","doi":"10.3390/geotechnics3040056","DOIUrl":"https://doi.org/10.3390/geotechnics3040056","url":null,"abstract":"One common method of estimating emax and emin for mixtures of sand and silt requires that the values of several empirical constants be determined. These empirical constants are the filling coefficients, a, and embedment coefficients, b, which can be determined either via lab testing or correlations. The study reported here developed simple correlations for estimating the filling and embedment coefficients using readily obtained laboratory data. These models were found to be excellent in producing filling and embedment coefficients that accurately predicted values of the index void ratios for sand and silt mixtures, with most R2 values being 0.94 or greater.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"164 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135251452","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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