H. Samadi-Boroujeni, A. Haghshenas-Adarmanabadi, M. Shayannejad, H. Khabbaz
This paper presents the settlement behaviour of Karkheh earth dam during its construction and operation stages. Karkheh is one of the largest earth dams in the world in terms of its reservoir capacity and body volume. The settlement of such a large body of soil can affect the performance of the dam elements and endanger downstream areas; should a breach or failure occur in the dam, more than two million people will be affected. It is crucial to know the settlement behaviour of this structure and use the existing results to predict its future settlements and calibrate the existing stress-strain models. For anticipation of dam settlement the measured displacement from the portable probe anchor magnets installed in the dam body are compared to the results of numerical simulations. The available data cover a period of 12 years including construction, and two material impounding and operation periods of the dam. The numerical analysis is performed in 2D plane-strain conditions and two material models are used, including Mohr-Coulomb (MC) and Hardening Soil (HS) models. The comparison between the calculation results and the measured vertical deformations in the dam site reveals that the accuracy of model for the deformations in the middle levels of dam is better than those of the crest for both applied material models in construction and impounding stages. The maximum settlement differences between computed and observed values are 0.05 m for MC model and 0.01 m for HS model. For the operation stage, the error of calculated settlements for the MC model is smaller; hence the results of this model might be more reliable for prediction of future dam settlements. The similar trends, obtained from both material models, exhibit the suitability of the model parameters used in the simulations.
{"title":"Comparison of Mohr-Coulomb and hardening soil constitutive models for simulation of settlements in the Karkheh earth dam","authors":"H. Samadi-Boroujeni, A. Haghshenas-Adarmanabadi, M. Shayannejad, H. Khabbaz","doi":"10.56295/agj5836","DOIUrl":"https://doi.org/10.56295/agj5836","url":null,"abstract":"This paper presents the settlement behaviour of Karkheh earth dam during its construction and operation stages. Karkheh is one of the largest earth dams in the world in terms of its reservoir capacity and body volume. The settlement of such a large body of soil can affect the performance of the dam elements and endanger downstream areas; should a breach or failure occur in the dam, more than two million people will be affected. It is crucial to know the settlement behaviour of this structure and use the existing results to predict its future settlements and calibrate the existing stress-strain models. For anticipation of dam settlement the measured displacement from the portable probe anchor magnets installed in the dam body are compared to the results of numerical simulations. The available data cover a period of 12 years including construction, and two material impounding and operation periods of the dam. The numerical analysis is performed in 2D plane-strain conditions and two material models are used, including Mohr-Coulomb (MC) and Hardening Soil (HS) models. The comparison between the calculation results and the measured vertical deformations in the dam site reveals that the accuracy of model for the deformations in the middle levels of dam is better than those of the crest for both applied material models in construction and impounding stages. The maximum settlement differences between computed and observed values are 0.05 m for MC model and 0.01 m for HS model. For the operation stage, the error of calculated settlements for the MC model is smaller; hence the results of this model might be more reliable for prediction of future dam settlements. The similar trends, obtained from both material models, exhibit the suitability of the model parameters used in the simulations.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46391703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ACARP Report C4057 (Eckersley, 2000) describes flowslides and other stability issues in stockpiles of coking (metallurgical) coal at Australian coal operations and export terminals, and summarizes 1973 to 2000 research at James Cook University (JCU). Eckersley (2022) partly updated that work with SEEP/W transient seepage modelling of a 12m high coal stockpile constructed at Hay Point in late 1991. Eckersley (2023) summarized available laboratory strength data for saturated and unsaturated coking coal to assist in selection and critical assessment of parameters for slope stability analyses of coal stockpiles. The current paper explores application of this data to stability analyses of two instrumented experimental stockpiles constructed at Hay Point, one of which collapsed suddenly and completely by flowsliding after extensive wetting. The stability analysis results tentatively confirm that the parameters and approach proposed are reasonable where stockpiles are subject to potential liquefaction-induced collapse. Significant questions raised by Eckersley (2023) regarding how the coking coal strength data should be applied are considered in the context of the stability analyses. The analyses tentatively confirm that effective strength parameters for saturated coal derived from peak deviator stress in isotropically consolidated, undrained (CIU), strain controlled triaxial tests are reasonable. For loose saturated coal these are at low strains and substantially less than critical state values. However, for unsaturated coal forming the bulk of a stockpile, unsaturated strength and apparent cohesion should be assessed from the effective friction angle at critical state and not the value mobilized at low strains. Use of total stress parameters derived from testing unsaturated coal may over-estimate factor of safety.
{"title":"Shear strength of stockpiled coking coal – Insights from stability analysis of two instrumented stockpiles","authors":"John David Eckersley","doi":"10.56295/agj5832","DOIUrl":"https://doi.org/10.56295/agj5832","url":null,"abstract":"ACARP Report C4057 (Eckersley, 2000) describes flowslides and other stability issues in stockpiles of coking (metallurgical) coal at Australian coal operations and export terminals, and summarizes 1973 to 2000 research at James Cook University (JCU). Eckersley (2022) partly updated that work with SEEP/W transient seepage modelling of a 12m high coal stockpile constructed at Hay Point in late 1991. Eckersley (2023) summarized available laboratory strength data for saturated and unsaturated coking coal to assist in selection and critical assessment of parameters for slope stability analyses of coal stockpiles. The current paper explores application of this data to stability analyses of two instrumented experimental stockpiles constructed at Hay Point, one of which collapsed suddenly and completely by flowsliding after extensive wetting. The stability analysis results tentatively confirm that the parameters and approach proposed are reasonable where stockpiles are subject to potential liquefaction-induced collapse. Significant questions raised by Eckersley (2023) regarding how the coking coal strength data should be applied are considered in the context of the stability analyses. The analyses tentatively confirm that effective strength parameters for saturated coal derived from peak deviator stress in isotropically consolidated, undrained (CIU), strain controlled triaxial tests are reasonable. For loose saturated coal these are at low strains and substantially less than critical state values. However, for unsaturated coal forming the bulk of a stockpile, unsaturated strength and apparent cohesion should be assessed from the effective friction angle at critical state and not the value mobilized at low strains. Use of total stress parameters derived from testing unsaturated coal may over-estimate factor of safety.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43069438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rolling dynamic compaction (RDC) is a specific type of dynamic compaction, which involves towing a heavy non-circular module at a relatively constant speed. This paper investigates the effects of module mass, operating speed and varying ground conditions on the effectiveness of the 4-sided impact roller using a developed finite element method (FEM)-discrete element method (DEM) model. Numerical results were analysed from four aspects, namely the energy imparted to the ground, soil velocity vectors, module imprint lengths and soil displacements at different depths. It is found that, a heavier module mass induces greater ground improvement in terms of both energy delivered to the soil per impact and the magnitude of soil displacements. The energy imparted to the underlying soil by the module increases with greater operating speed. The rotational dynamics of the module also change with increasing operating speed, whereby the impacts are delivered by the faces of the module at typical operating speeds; however, at faster speeds the impacts are delivered towards the corners of the module and the behaviour is less reproducible. The modelling showed that soil with a higher initial Young’s modulus and a higher internal angle of friction decreases the magnitude of soil displacements, which confirms that the impact roller is less able to significantly improve soils that are stiff or have a high initial shear strength.
{"title":"A numerical parametric study of the effectiveness of the 4-sided impact roller","authors":"Yue Chen, M. Jaksa, B. Scott, Y. Kuo","doi":"10.56295/agj5822","DOIUrl":"https://doi.org/10.56295/agj5822","url":null,"abstract":"Rolling dynamic compaction (RDC) is a specific type of dynamic compaction, which involves towing a heavy non-circular module at a relatively constant speed. This paper investigates the effects of module mass, operating speed and varying ground conditions on the effectiveness of the 4-sided impact roller using a developed finite element method (FEM)-discrete element method (DEM) model. Numerical results were analysed from four aspects, namely the energy imparted to the ground, soil velocity vectors, module imprint lengths and soil displacements at different depths. It is found that, a heavier module mass induces greater ground improvement in terms of both energy delivered to the soil per impact and the magnitude of soil displacements. The energy imparted to the underlying soil by the module increases with greater operating speed. The rotational dynamics of the module also change with increasing operating speed, whereby the impacts are delivered by the faces of the module at typical operating speeds; however, at faster speeds the impacts are delivered towards the corners of the module and the behaviour is less reproducible. The modelling showed that soil with a higher initial Young’s modulus and a higher internal angle of friction decreases the magnitude of soil displacements, which confirms that the impact roller is less able to significantly improve soils that are stiff or have a high initial shear strength.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49174489","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Little published information is available on bond stress parameters at the grout-ground interface for the design of ground anchors within Brisbane rocks. In the absence of data, a designer will typically fall back to ‘universal’ correlations with measurable parameters such as Uniaxial Compressive Strength (UCS) or descriptions of rock type to nominate design bond stress values. In doing so, there is often little understanding of the limitations of such correlations or how applicable those correlations are for the rocks encountered within the local region. A study of Proof Test data from testing of sacrificial ground anchors constructed within materials from the Brisbane Tuff and Neranleigh Fernvale Beds Stratigraphic Units for an infrastructure project in Brisbane has been carried out to consider bond stress values at the grout-ground interface. Materials within the bond zone of ground anchors constructed in Brisbane Tuff and Neranleigh Fernvale Beds units have been classified into different rock units based on rock substance strength and Geological Strength Index. Details of anchor construction and testing procedures are presented, together with the adopted approach to test interpretation. Data from Proof Testing of ground anchors bonded into these materials is then interpreted and evaluated for each unit, with relationships developed for each rock type for ultimate and yield bond stress values at the grout-ground interface as a function of rock substance strength (UCS) and rock mass strength (based on Hoek and Brown,2018). For both rock types, grout-ground interface bond stresses increase with rock strength and quality, with better correlations evident based on rock mass strength than for UCS data. Comparisons of the interpreted bond stress relationships based on UCS are made for both rock types to published information for ground anchors and shaft adhesion parameters for cast-in-situ piles. Suggestions are made for amendments to the Proof Anchor test method to reduce the potential for premature termination of the test and consequent underestimation of the bond stress, and to obtain consistency between Proof and Production test methods.
{"title":"Design bond stress parameters for rock anchors in Brisbane","authors":"G. Hackney, M. Sadeghi, Stephanie Neller","doi":"10.56295/agj5824","DOIUrl":"https://doi.org/10.56295/agj5824","url":null,"abstract":"Little published information is available on bond stress parameters at the grout-ground interface for the design of ground anchors within Brisbane rocks. In the absence of data, a designer will typically fall back to ‘universal’ correlations with measurable parameters such as Uniaxial Compressive Strength (UCS) or descriptions of rock type to nominate design bond stress values. In doing so, there is often little understanding of the limitations of such correlations or how applicable those correlations are for the rocks encountered within the local region. A study of Proof Test data from testing of sacrificial ground anchors constructed within materials from the Brisbane Tuff and Neranleigh Fernvale Beds Stratigraphic Units for an infrastructure project in Brisbane has been carried out to consider bond stress values at the grout-ground interface. Materials within the bond zone of ground anchors constructed in Brisbane Tuff and Neranleigh Fernvale Beds units have been classified into different rock units based on rock substance strength and Geological Strength Index. Details of anchor construction and testing procedures are presented, together with the adopted approach to test interpretation. Data from Proof Testing of ground anchors bonded into these materials is then interpreted and evaluated for each unit, with relationships developed for each rock type for ultimate and yield bond stress values at the grout-ground interface as a function of rock substance strength (UCS) and rock mass strength (based on Hoek and Brown,2018). For both rock types, grout-ground interface bond stresses increase with rock strength and quality, with better correlations evident based on rock mass strength than for UCS data. Comparisons of the interpreted bond stress relationships based on UCS are made for both rock types to published information for ground anchors and shaft adhesion parameters for cast-in-situ piles. Suggestions are made for amendments to the Proof Anchor test method to reduce the potential for premature termination of the test and consequent underestimation of the bond stress, and to obtain consistency between Proof and Production test methods.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42428226","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The paper looks at the stability of fill embankments using data from failed embankments constructed from residual soils in Western Sydney. Semi-quantitative, deterministic and probabilistic methods are used to consider the stability of such fill embankments. A simple, infinite slope model was adopted to carry out deterministic and probabilistic analyses. Climate data was used to assess the likelihood of fill saturation and the impacts of climate change on predictions.
{"title":"Stability of earth fill embankments constructed from residual soils including impacts of climate change","authors":"P. Waddell","doi":"10.56295/agj5821","DOIUrl":"https://doi.org/10.56295/agj5821","url":null,"abstract":"The paper looks at the stability of fill embankments using data from failed embankments constructed from residual soils in Western Sydney. Semi-quantitative, deterministic and probabilistic methods are used to consider the stability of such fill embankments. A simple, infinite slope model was adopted to carry out deterministic and probabilistic analyses. Climate data was used to assess the likelihood of fill saturation and the impacts of climate change on predictions.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43352107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Established relationships between the coefficient of consolidation (cv) and index tests are used during both preliminary design and as a cross check during detailed design. The laboratory oedometer test provides compressibility parameters and a lower bound of cv, while the coefficients of consolidation are preferred from the field dissipation tests. However, cv is dependent on the method used to determine its value, stress level, and over-consolidation ratio. In practice, the coefficient of consolidation values obtained from dissipation tests are used to predict settlement time, while oedometer tests are useful in obtaining the parameter required to predict the magnitude of settlement. However, dissipation tests measure the horizontal coefficient of consolidation (ch) which needs to be related back to the vertical value. These standard approaches are discussed using test data from Queensland sites. Inconsistencies in correlations are used to show that design should consider the wide variability in interpretations that can occur, and correlations of cv with index tests should not be used in detailed design. Additionally, the cv values obtained from oedometer testing is a poor predictor of time for consolidation. This could also be due to the size of samples being not large enough for the soil structure. Monitoring data from construction sites are used to assess a “moderately” conservative design value from dissipation and lab tests.
{"title":"Assessment of the coefficient of consolidation with Queensland data","authors":"B. Look","doi":"10.56295/agj5825","DOIUrl":"https://doi.org/10.56295/agj5825","url":null,"abstract":"Established relationships between the coefficient of consolidation (cv) and index tests are used during both preliminary design and as a cross check during detailed design. The laboratory oedometer test provides compressibility parameters and a lower bound of cv, while the coefficients of consolidation are preferred from the field dissipation tests. However, cv is dependent on the method used to determine its value, stress level, and over-consolidation ratio. In practice, the coefficient of consolidation values obtained from dissipation tests are used to predict settlement time, while oedometer tests are useful in obtaining the parameter required to predict the magnitude of settlement. However, dissipation tests measure the horizontal coefficient of consolidation (ch) which needs to be related back to the vertical value. These standard approaches are discussed using test data from Queensland sites. Inconsistencies in correlations are used to show that design should consider the wide variability in interpretations that can occur, and correlations of cv with index tests should not be used in detailed design. Additionally, the cv values obtained from oedometer testing is a poor predictor of time for consolidation. This could also be due to the size of samples being not large enough for the soil structure. Monitoring data from construction sites are used to assess a “moderately” conservative design value from dissipation and lab tests.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47055974","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Department of Transport and Main Roads (TMR), Engineering and Technology's (E&T) Geotechnical Section, have completed a research-based field trial aimed at developing a repeatable methodology to carry out geotechnical boreholes on steeply sloping ground. This has been presented in the context of slope failures, whereby the utilisation of this practise will provide subsurface information, which is directly representative of the area of interest, rather than that which is outside the landslide extent (current general practise within Australia). It is expected that the information gained from adopting this practice will enable optimum design and remediation treatments for landslides within Australia, and subsequently contribute strongly to sustainable project outcomes.
{"title":"Borehole investigation on steep sloping ground","authors":"Jun Sugawara, Daniel Colborne, Mogana Sundaram","doi":"10.56295/agj5823","DOIUrl":"https://doi.org/10.56295/agj5823","url":null,"abstract":"The Department of Transport and Main Roads (TMR), Engineering and Technology's (E&T) Geotechnical Section, have completed a research-based field trial aimed at developing a repeatable methodology to carry out geotechnical boreholes on steeply sloping ground. This has been presented in the context of slope failures, whereby the utilisation of this practise will provide subsurface information, which is directly representative of the area of interest, rather than that which is outside the landslide extent (current general practise within Australia). It is expected that the information gained from adopting this practice will enable optimum design and remediation treatments for landslides within Australia, and subsequently contribute strongly to sustainable project outcomes.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135983147","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To support our civilisation’s requirement for carbon steel, longwall mining of the Bulli Seam at Appin and Tahmoor Collieries has occurred to recover high quality coking/metallurgical coal, being for steelmaking. The Main Southern Railway crosses the footprint of both mines, and it was therefore important to manage the risk to infrastructure and public safety during longwall retreat in this strain-driven environment. One technical issue is the response to subsidence-induced ‘valley closure’. This has occurred in both gently undulating Wianamatta Group Ashfield Shale and the steeper upper Hawkesbury Sandstone valleys. This paper covers the observed responses of embankments on the Main Southern Railway and the heritage railway Picton to Mittagong Loop Line, and illustrates the responses of the embankments to valley closure that produced up to 11% strain, as well as illustrating displacement field development and derived principal strain vectors. The responses of four embankments are presented beneath which longwalls have been successfully extracted, and done so without adverse impact upon public safety. An understanding of the strain-driven responses of the embankments is presented.
{"title":"Responses Of Free-Standing Railway Embankments As A Consequence Of Mine Subsidence In The NSW Southern Coalfield","authors":"A. Leventhal, T. Hull, R. Walsh, Ross Barber","doi":"10.56295/agj5813","DOIUrl":"https://doi.org/10.56295/agj5813","url":null,"abstract":"To support our civilisation’s requirement for carbon steel, longwall mining of the Bulli Seam at Appin and Tahmoor Collieries has occurred to recover high quality coking/metallurgical coal, being for steelmaking. The Main Southern Railway crosses the footprint of both mines, and it was therefore important to manage the risk to infrastructure and public safety during longwall retreat in this strain-driven environment. One technical issue is the response to subsidence-induced ‘valley closure’. This has occurred in both gently undulating Wianamatta Group Ashfield Shale and the steeper upper Hawkesbury Sandstone valleys. This paper covers the observed responses of embankments on the Main Southern Railway and the heritage railway Picton to Mittagong Loop Line, and illustrates the responses of the embankments to valley closure that produced up to 11% strain, as well as illustrating displacement field development and derived principal strain vectors. The responses of four embankments are presented beneath which longwalls have been successfully extracted, and done so without adverse impact upon public safety. An understanding of the strain-driven responses of the embankments is presented.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44600853","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sugarcane is the second largest export crop in Australia. Industrial production of sugar, from sugarcane, results in bagasse fly ash (BFA), a by-product from the cogeneration in sugar milling operations that generate electricity by steam. The chemical and physical properties of BFA highlight its potential as a promising pozzolan for the stabilization of expansive soils, due primarily to a high content and surface area of the amorphous silicate found in BFA. Silicate in bagasse fly ash reacts extensively with calcium hydrate in lime to produce hydrated products via pozzolanic reactions, this results in a hardening of the material to which BFA and lime have been added. This reaction has been studied to be a function of the size of BFA particles and conditions of the curing process. This study explored the variables that influence the reaction and evaluated shrinkage and compressive strength of the mixtures to which bagasse fly ash, in the form of different particle size distributions, and hydrated lime are added. The maximum BFA particles sizes considered within this study include 75, 150 and 425 μm; curing times of 7 and 28 days are also explored. A suite of testing, including Atterberg limits, linear shrinkage (LS), and unconfined compressive strength (UCS) tests were completed on the prepared mixtures. The findings indicate that bagasse fly ash with a maximum size of 425 μm yields a higher UCS and lower LS, compared to finer BFA particle mixtures. The ash with a maximum particle size of 425-μm also improves the ductility of treated soils and accelerates their strength gain, compared to soil- lime stabilized samples. The results of the study build towards a better understanding of BFA, and the ways in which such a material maybe engineered to replace concrete in road work projects and other applications involving expansive soils.
{"title":"The Influence Of Bagasse Fly Ash Particle Size In Controlling Expansive Soils In Combination With Hydrated Lime","authors":"T. Le, Sachit A. J. Desa, H. Khabbaz","doi":"10.56295/agj5812","DOIUrl":"https://doi.org/10.56295/agj5812","url":null,"abstract":"Sugarcane is the second largest export crop in Australia. Industrial production of sugar, from sugarcane, results in bagasse fly ash (BFA), a by-product from the cogeneration in sugar milling operations that generate electricity by steam. The chemical and physical properties of BFA highlight its potential as a promising pozzolan for the stabilization of expansive soils, due primarily to a high content and surface area of the amorphous silicate found in BFA. Silicate in bagasse fly ash reacts extensively with calcium hydrate in lime to produce hydrated products via pozzolanic reactions, this results in a hardening of the material to which BFA and lime have been added. This reaction has been studied to be a function of the size of BFA particles and conditions of the curing process. This study explored the variables that influence the reaction and evaluated shrinkage and compressive strength of the mixtures to which bagasse fly ash, in the form of different particle size distributions, and hydrated lime are added. The maximum BFA particles sizes considered within this study include 75, 150 and 425 μm; curing times of 7 and 28 days are also explored. A suite of testing, including Atterberg limits, linear shrinkage (LS), and unconfined compressive strength (UCS) tests were completed on the prepared mixtures. The findings indicate that bagasse fly ash with a maximum size of 425 μm yields a higher UCS and lower LS, compared to finer BFA particle mixtures. The ash with a maximum particle size of 425-μm also improves the ductility of treated soils and accelerates their strength gain, compared to soil- lime stabilized samples. The results of the study build towards a better understanding of BFA, and the ways in which such a material maybe engineered to replace concrete in road work projects and other applications involving expansive soils.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49486221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The use of biopolymers to enhance the engineering properties of soil has received increasing attention in recent years, however, the interactive role that biopolymers and the fines content of the soil play in governing the geotechnical parameters still requires insightful investigation, in relation to chemical soil treatment that can be ecologically detrimental. This paper examines the combined effects of Xanthan Gum (XG) derived from specific bacterial strains and the presence of clay fines content (kaolin) on the strength and stiffness of low plasticity soils, with special reference of cyclic traffic (road and rail) loading. In this study, fine sand is mixed with different contents of kaolin, whereby laboratory compression and tensile tests were conducted on natural (untreated) and XG-treated soil specimens. The results indicate that soil strength can be enhanced significantly when XG is added, however the effectiveness is a function of the kaolin content (KC). At an optimum XG content of 2% and a fines content increasing from 5% to 30%, split tensile strength increases from 230 to 750 kPa,while the unconfined compressive strength rises from 1.4 to 7.9 MPa, respectively. For XG content between 0.5% and 2%, the small strain stiffness of treated soil increases fourfold from 206 to 854 MPa.
{"title":"Effects Of Fines Content On The Strength And Stiffness Of Biopolymer Treated Low-Plasticity Soils","authors":"R. Gedela, B. Indraratna, S. Medawela, T. Nguyen","doi":"10.56295/agj5811","DOIUrl":"https://doi.org/10.56295/agj5811","url":null,"abstract":"The use of biopolymers to enhance the engineering properties of soil has received increasing attention in recent years, however, the interactive role that biopolymers and the fines content of the soil play in governing the geotechnical parameters still requires insightful investigation, in relation to chemical soil treatment that can be ecologically detrimental. This paper examines the combined effects of Xanthan Gum (XG) derived from specific bacterial strains and the presence of clay fines content (kaolin) on the strength and stiffness of low plasticity soils, with special reference of cyclic traffic (road and rail) loading. In this study, fine sand is mixed with different contents of kaolin, whereby laboratory compression and tensile tests were conducted on natural (untreated) and XG-treated soil specimens. The results indicate that soil strength can be enhanced significantly when XG is added, however the effectiveness is a function of the kaolin content (KC). At an optimum XG content of 2% and a fines content increasing from 5% to 30%, split tensile strength increases from 230 to 750 kPa,while the unconfined compressive strength rises from 1.4 to 7.9 MPa, respectively. For XG content between 0.5% and 2%, the small strain stiffness of treated soil increases fourfold from 206 to 854 MPa.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44277093","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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