The bearing capacity of shallow foundations on layered soils is typically based on empirical models assuming a strip footing. Shape factors are then applied to the strip footing solution to account for the specific geometry of the foundation being considered. A common practical application of this methodology is when the ultimate bearing capacity of a granular working platform constructed over a clay subgrade is estimated using the Working Platforms for Tracked Plant BRE-470 guideline. Previous studies using finite element limit analysis have been undertaken to examine a strip footing on a layered soil and how the resulting bearing capacity compares to that derived from BRE-470. This paper presents an extension of previous work by the authors using finite element limit analysis to investigate the three-dimensional influence on the bearing capacity of square and rectangular footings on sand over clay. The finite element limit analysis solutions are used to produce charts to assist designers with estimating the ultimate bearing capacity of granular working platforms overlying clay. The paper also aims to highlight some important considerations when adopting the BRE-470 guideline to design granular working platforms overlying clay.
{"title":"Working platforms and bearing capacity assessments of sand overlying clay using finite element limit analysis","authors":"Sean Goodall, R. Merifield","doi":"10.56295/agj5835","DOIUrl":"https://doi.org/10.56295/agj5835","url":null,"abstract":"The bearing capacity of shallow foundations on layered soils is typically based on empirical models assuming a strip footing. Shape factors are then applied to the strip footing solution to account for the specific geometry of the foundation being considered. A common practical application of this methodology is when the ultimate bearing capacity of a granular working platform constructed over a clay subgrade is estimated using the Working Platforms for Tracked Plant BRE-470 guideline. Previous studies using finite element limit analysis have been undertaken to examine a strip footing on a layered soil and how the resulting bearing capacity compares to that derived from BRE-470. This paper presents an extension of previous work by the authors using finite element limit analysis to investigate the three-dimensional influence on the bearing capacity of square and rectangular footings on sand over clay. The finite element limit analysis solutions are used to produce charts to assist designers with estimating the ultimate bearing capacity of granular working platforms overlying clay. The paper also aims to highlight some important considerations when adopting the BRE-470 guideline to design granular working platforms overlying clay.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":" ","pages":""},"PeriodicalIF":0.2,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47878368","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}
Flowslides and stability issues have occurred periodically within stockpiles of coking (metallurgical) coal at coal processing plants and export terminals in Queensland’s Bowen Basin, and to a lesser degree in New South Wales, since the early 1970s. A description of the issue and summary of research at James Cook University (JCU) from 1973 to 2000 was published in ACARP Report C4057 (Eckersley, 2000). Eckersley (2022) partly updated that work with SEEP/W transient seepage modelling of a 12 m high coal stockpile constructed at Hay Point in late 1991 for which initial moisture content, pore water pressures at the stockpile base, outflows from subsoil drains and final density and moisture profiles were measured. This provided a good starting point for modelling of moisture movements within production coal stockpiles as required for meaningful slope stability analyses. The current paper provides an accessible summary of available data from laboratory shear strength testing of coking coal to assist in selection and critical assessment of parameters for slope stability analyses of coal stockpiles. This includes data for saturated coal likely to form the base of a stockpile and currently limited data for unsaturated coal forming the bulk of a stockpile. It then highlights some issues in the selection of parameters for stability analyses of coal stockpiles.
自20世纪70年代初以来，昆士兰州Bowen盆地的煤炭加工厂和出口码头的炼焦(冶金)煤库存定期发生流滑和稳定性问题，新南威尔士州的情况较轻。ACARP Report C4057 (Eckersley, 2000)对James Cook University (JCU)从1973年到2000年的问题和研究总结进行了描述。Eckersley(2022)部分更新了1991年末在Hay Point建造的12米高煤库的SEEP/W瞬态渗流模型，其中测量了初始水分含量，储存基地的孔隙水压力，底土排水的流出量以及最终密度和水分剖面。这为有意义的边坡稳定性分析所需的生产煤库存中的水分运动建模提供了一个良好的起点。本文提供了炼焦煤实验室抗剪强度测试的可用数据摘要，以协助煤库边坡稳定性分析参数的选择和关键评估。这包括可能构成库存基础的饱和煤的数据，以及构成库存主体的不饱和煤目前有限的数据。重点介绍了煤炭库存稳定性分析参数选择中的一些问题。
{"title":"Shear strength of stockpiled coking coal – Existing data","authors":"John David Eckersley","doi":"10.56295/agj5831","DOIUrl":"https://doi.org/10.56295/agj5831","url":null,"abstract":"Flowslides and stability issues have occurred periodically within stockpiles of coking (metallurgical) coal at coal processing plants and export terminals in Queensland’s Bowen Basin, and to a lesser degree in New South Wales, since the early 1970s. A description of the issue and summary of research at James Cook University (JCU) from 1973 to 2000 was published in ACARP Report C4057 (Eckersley, 2000). Eckersley (2022) partly updated that work with SEEP/W transient seepage modelling of a 12 m high coal stockpile constructed at Hay Point in late 1991 for which initial moisture content, pore water pressures at the stockpile base, outflows from subsoil drains and final density and moisture profiles were measured. This provided a good starting point for modelling of moisture movements within production coal stockpiles as required for meaningful slope stability analyses. The current paper provides an accessible summary of available data from laboratory shear strength testing of coking coal to assist in selection and critical assessment of parameters for slope stability analyses of coal stockpiles. This includes data for saturated coal likely to form the base of a stockpile and currently limited data for unsaturated coal forming the bulk of a stockpile. It then highlights some issues in the selection of parameters for stability analyses of coal stockpiles.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":" ","pages":""},"PeriodicalIF":0.2,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45218218","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 1931 Dogface Rock landslide in Katoomba NSW was a complex, progressive cliff collapse with a failure volume in the order of 100,000 m3 that was triggered by the extraction of remnant coal pillars from the Katoomba Colliery, about 200 m below the top of the escarpment. Although underground coal mining is generally accepted as a cause of the rockslide, previous studies have not explicitly investigated the role of progressive brittle fracture in the collapse. This paper presents an integrated study which incorporates remotely piloted aircraft photogrammetry with a discrete element method numerical investigation of the landslide, and thereby explores the role of progressive brittle fracture, and re-examines the failure mechanism and runout motion of this multi-stage landslide. Remotely piloted aircraft photography is used to build a georeferenced 3D model of the site with Structure-from-Motion photogrammetry software. A digital geotechnical mapping workflow is demonstrated to investigate the morphology of the landslide scar, extract statistics on discontinuity orientation, persistence, and spacing, and undertake trace mapping of newer brittle fractures that interacted with pre-existing high persistence joints as the landslide rupture surface developed. A series of discrete element method numerical laboratory tests are used to calibrate bonded block contact properties that reproduce laboratory scale intact rock index parameters including UCS and tensile strength. Upscaled rock block contact parameters are then applied to a cliff-scale model that investigates the progressive development of rock mass damage induced by mining. Following extraction of the remnant pillars, rock mass damage develops mostly by extensile strains that produce tension cracks. Brittle fractures propagate upwards from the mine level and eventually initiate toppling of massive sandstone slabs defined by high persistence pre-existing subvertical joints. The investigation illustrates how the integration of photogrammetry with discrete element numerical methods can be used to characterise progressive brittle failure and runout of large rock slope failures.
{"title":"The role of progressive brittle fracture in the 1931 landslide at Dogface Rock, Katoomba","authors":"Z. Tuckey","doi":"10.56295/agj5833","DOIUrl":"https://doi.org/10.56295/agj5833","url":null,"abstract":"The 1931 Dogface Rock landslide in Katoomba NSW was a complex, progressive cliff collapse with a failure volume in the order of 100,000 m3 that was triggered by the extraction of remnant coal pillars from the Katoomba Colliery, about 200 m below the top of the escarpment. Although underground coal mining is generally accepted as a cause of the rockslide, previous studies have not explicitly investigated the role of progressive brittle fracture in the collapse. This paper presents an integrated study which incorporates remotely piloted aircraft photogrammetry with a discrete element method numerical investigation of the landslide, and thereby explores the role of progressive brittle fracture, and re-examines the failure mechanism and runout motion of this multi-stage landslide. Remotely piloted aircraft photography is used to build a georeferenced 3D model of the site with Structure-from-Motion photogrammetry software. A digital geotechnical mapping workflow is demonstrated to investigate the morphology of the landslide scar, extract statistics on discontinuity orientation, persistence, and spacing, and undertake trace mapping of newer brittle fractures that interacted with pre-existing high persistence joints as the landslide rupture surface developed. A series of discrete element method numerical laboratory tests are used to calibrate bonded block contact properties that reproduce laboratory scale intact rock index parameters including UCS and tensile strength. Upscaled rock block contact parameters are then applied to a cliff-scale model that investigates the progressive development of rock mass damage induced by mining. Following extraction of the remnant pillars, rock mass damage develops mostly by extensile strains that produce tension cracks. Brittle fractures propagate upwards from the mine level and eventually initiate toppling of massive sandstone slabs defined by high persistence pre-existing subvertical joints. The investigation illustrates how the integration of photogrammetry with discrete element numerical methods can be used to characterise progressive brittle failure and runout of large rock slope failures.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":" ","pages":""},"PeriodicalIF":0.2,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47196092","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 consolidation characteristics of cohesive soils are estimated using established relationships between the coefficient of consolidation (cv) and index tests, as well as laboratory oedometer tests. While the design cv is preferred from the field dissipation tests, the conversion from a horizontal to vertical value needs to be considered. A trial load was used to verify the consolidation parameters during a Queensland Road upgrade, which involved both road widening and raising of the existing embankments over compressible soils. Construction was done in 4 stages, and with preloading and surcharging in selected areas. Settlement monitoring and Asaoka plots were used to validate the design, and “moderately conservative” design values were adopted. This case study is used to show the large variability of the cv by the various test methods. While 99% of the site settlement was within the magnitude and time predicted during design, a 25 m length was not consistent with the data and performance of the rest of this site within the flood plain. The back-calculated cv was below the lowest test value and even data from nearby settlement plate monitoring from adjacent stages. In situ tests were located within 25m of this unconforming area and given that stratigraphy was consistent then the cv value adopted may not be representative. The lessons learnt show the various verification and validation process required to envelope risks, but all conditions with a “moderately conservative” design may not be covered.
{"title":"A case study on the variability of the coefficient of consolidation and its design reliability","authors":"B. Look","doi":"10.56295/agj5834","DOIUrl":"https://doi.org/10.56295/agj5834","url":null,"abstract":"The consolidation characteristics of cohesive soils are estimated using established relationships between the coefficient of consolidation (cv) and index tests, as well as laboratory oedometer tests. While the design cv is preferred from the field dissipation tests, the conversion from a horizontal to vertical value needs to be considered. A trial load was used to verify the consolidation parameters during a Queensland Road upgrade, which involved both road widening and raising of the existing embankments over compressible soils. Construction was done in 4 stages, and with preloading and surcharging in selected areas. Settlement monitoring and Asaoka plots were used to validate the design, and “moderately conservative” design values were adopted. This case study is used to show the large variability of the cv by the various test methods. While 99% of the site settlement was within the magnitude and time predicted during design, a 25 m length was not consistent with the data and performance of the rest of this site within the flood plain. The back-calculated cv was below the lowest test value and even data from nearby settlement plate monitoring from adjacent stages. In situ tests were located within 25m of this unconforming area and given that stratigraphy was consistent then the cv value adopted may not be representative. The lessons learnt show the various verification and validation process required to envelope risks, but all conditions with a “moderately conservative” design may not be covered.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":" ","pages":""},"PeriodicalIF":0.2,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49030260","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}
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":" ","pages":""},"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":" ","pages":""},"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":" ","pages":""},"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":"1 1","pages":""},"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":" ","pages":""},"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":" ","pages":""},"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}
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