P. Flentje, Connor Larkin, Damian Mulcahy, Larissa Hettiarachchi, Daniel M. Horan, James Cox, Stuart Milling, Peter Tobin, Kevin Bogie
Eastern Australia has experienced a significant magnitude rainfall event of extended duration in the first 7 months of 2022. Across the east coast of New South Wales (NSW) a series of troughs and East Coast Lows occurred during a La Nina weather cycle bringing above average rainfall to the region. As this first half of 2022 La Nina event was drawing to a close the Indian Ocean Dipole entered a negative phase which coincided with another intense East Coast Low in early July 2022 impacting the Illawarra region of NSW. These events caused widespread flooding and significant landslide damage to road and rail infrastructure across the state networks and local government infrastructure across NSW. During this extended wet period in the first 7 months of 2022 more than 200 landslides have been recorded across the Illawarra, Southern Highlands and Blue Mountains regions of NSW whilst many more have occurred across the north coast region. This paper presents a brief and albeit preliminary summary of the rainfall and provides a series of photographs with very brief descriptions of some of these landslide events within southeastern NSW. The intent of the paper is to provide early guidance to AGS members of the nature and form of landslides that have occurred across the Illawarra region. This paper does not discuss the dual fatality resulting from the Wentworth Falls area rockfall of the 5th April.
{"title":"A Photographic Essay on Landslides Across Southeastern New South Wales Triggered by the Rainfull Events of 2022","authors":"P. Flentje, Connor Larkin, Damian Mulcahy, Larissa Hettiarachchi, Daniel M. Horan, James Cox, Stuart Milling, Peter Tobin, Kevin Bogie","doi":"10.56295/agj5736","DOIUrl":"https://doi.org/10.56295/agj5736","url":null,"abstract":"Eastern Australia has experienced a significant magnitude rainfall event of extended duration in the first 7 months of 2022. Across the east coast of New South Wales (NSW) a series of troughs and East Coast Lows occurred during a La Nina weather cycle bringing above average rainfall to the region. As this first half of 2022 La Nina event was drawing to a close the Indian Ocean Dipole entered a negative phase which coincided with another intense East Coast Low in early July 2022 impacting the Illawarra region of NSW. These events caused widespread flooding and significant landslide damage to road and rail infrastructure across the state networks and local government infrastructure across NSW. During this extended wet period in the first 7 months of 2022 more than 200 landslides have been recorded across the Illawarra, Southern Highlands and Blue Mountains regions of NSW whilst many more have occurred across the north coast region. This paper presents a brief and albeit preliminary summary of the rainfall and provides a series of photographs with very brief descriptions of some of these landslide events within southeastern NSW. The intent of the paper is to provide early guidance to AGS members of the nature and form of landslides that have occurred across the Illawarra region. This paper does not discuss the dual fatality resulting from the Wentworth Falls area rockfall of the 5th April.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47720581","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 from 1973 to 2000 was published in ACARP Report C4057. Despite this work, coal stockpile flowslides remain a significant risk at mine and port stockpiles due to their initiation without warning and dramatic consequences. To be able to adequately model the redistribution of moisture that leads to collapse of a stockpile and then conduct realistic stability analyses for design of preventative measures remains an elusive prospect. This paper therefore updates the previous work with results from SEEP/W transient seepage modelling within a 12m high 14,700 tonne coal stockpile constructed at Hay Point in late 1991 for which initial moisture content, pore pressures at the stockpile base, outflows from subsoil drains and final density and moisture profiles were measured. The model was based on results of laboratory permeability and column drainage tests on specimens taken from a composite bulk sample obtained at the time of stockpile construction. The coking coal product was from an operation with a known history of stockpile instability. Results were found to correspond well with pore pressures measured at the stockpile base and the stockpile’s final moisture profile provided account was taken of a thin higher permeability zone just above the subgrade. The approach adopted and parameters developed provide a significant advance in modelling of moisture movements within production coal stockpiles, with a view to subsequent slope stability analyses.
{"title":"Moisture Movement Analyses for Coal Stockpiles","authors":"J. Eckersley","doi":"10.56295/agj5731","DOIUrl":"https://doi.org/10.56295/agj5731","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 from 1973 to 2000 was published in ACARP Report C4057. Despite this work, coal stockpile flowslides remain a significant risk at mine and port stockpiles due to their initiation without warning and dramatic consequences. To be able to adequately model the redistribution of moisture that leads to collapse of a stockpile and then conduct realistic stability analyses for design of preventative measures remains an elusive prospect. This paper therefore updates the previous work with results from SEEP/W transient seepage modelling within a 12m high 14,700 tonne coal stockpile constructed at Hay Point in late 1991 for which initial moisture content, pore pressures at the stockpile base, outflows from subsoil drains and final density and moisture profiles were measured. The model was based on results of laboratory permeability and column drainage tests on specimens taken from a composite bulk sample obtained at the time of stockpile construction. The coking coal product was from an operation with a known history of stockpile instability. Results were found to correspond well with pore pressures measured at the stockpile base and the stockpile’s final moisture profile provided account was taken of a thin higher permeability zone just above the subgrade. The approach adopted and parameters developed provide a significant advance in modelling of moisture movements within production coal stockpiles, with a view to subsequent slope stability analyses.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46330692","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}
Battered minipile groups mimicking tree root networks have been gaining popularity as a footing solution for light structural applications in residential, commercial and infrastructure sectors, recently. Battered minipile group configurations are recently in the limelight due to advantages such as ease of installation and environmentally friendly nature. The lateral load resistance of battered minipile groups is investigated in this paper through a combination of physical and numerical modelling. Two-unconventional battered minipile groups with configurations representing the root network of trees with the capacity of engaging a larger volume of soil compared to conventional battered minipile group configurations are studied. A conventional battered minipile group is also included in the study to draw a direct comparison with the new minipile group configurations introduced in this paper. The conventional battered minipile group has two positively and two negatively 25° battered minipiles. The second type of group has one 25° perpendicularly battered minipile in the leading and trailing row each. Another unique orientation of the battered minipile group is also introduced in this study which has four diagonally outward 25° battered minipiles. The third type of minipile group with four diagonally outward battered minipiles offered the highest lateral resistance among the three groups. This better performance capability was attributed to the engagement of a larger volume of soil in resisting lateral load applied at the minipile head. Through this study, the industrial application of the unconventional minipile group configuration with better performance capability in terms of lateral load resistance can be advocated more confidently.
{"title":"Soil-Structure Interaction of Battered Minipile Groups in Sandy Soil","authors":"Sanchari Mondal, M. Disfani","doi":"10.56295/agj5738","DOIUrl":"https://doi.org/10.56295/agj5738","url":null,"abstract":"Battered minipile groups mimicking tree root networks have been gaining popularity as a footing solution for light structural applications in residential, commercial and infrastructure sectors, recently. Battered minipile group configurations are recently in the limelight due to advantages such as ease of installation and environmentally friendly nature. The lateral load resistance of battered minipile groups is investigated in this paper through a combination of physical and numerical modelling. Two-unconventional battered minipile groups with configurations representing the root network of trees with the capacity of engaging a larger volume of soil compared to conventional battered minipile group configurations are studied. A conventional battered minipile group is also included in the study to draw a direct comparison with the new minipile group configurations introduced in this paper. The conventional battered minipile group has two positively and two negatively 25° battered minipiles. The second type of group has one 25° perpendicularly battered minipile in the leading and trailing row each. Another unique orientation of the battered minipile group is also introduced in this study which has four diagonally outward 25° battered minipiles. The third type of minipile group with four diagonally outward battered minipiles offered the highest lateral resistance among the three groups. This better performance capability was attributed to the engagement of a larger volume of soil in resisting lateral load applied at the minipile head. Through this study, the industrial application of the unconventional minipile group configuration with better performance capability in terms of lateral load resistance can be advocated more confidently.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42030393","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}
Challenges in the extraction and use of earth resources and spaces are encountered given a growing worldwide population, rising infrastructures development, and widespread climate change. In Australia, mining and construction are two major bases for economic growth while both being traditional hazardous and heavy industries. A nation-wide infrastructure upgrade featuring large-scale underground development is underway, the geological uncertainties and localisation difficulties of already laid infrastructure are associated with challenges not seen in building construction. A safer and competent subterranean transport solution is yet proposed in the context of sustainable developments. In light of this, geotechnical analysis as a fundamental subject for developing and maintaining safe and sustainable use of underground space has huge potential to be undertaken more intuitively considering the advancements in information management and visualisation. The PhD work examines the state-of-the-art applications, limitations and future opportunities of Building Information Modelling (BIM) and other computational techniques in the digitisation of tunnelling and underground construction. The visualisation and interoperability facilitated by data-driven processes are especially important to underground construction that engages interdisciplinary and multi-environment interaction.
{"title":"Digital Twin for Underground Stations : Improving Decision Making for Construction Lifecycle","authors":"Mengqi Huang, J. Ninić, Qianbing Zhang","doi":"10.56295/agj5737","DOIUrl":"https://doi.org/10.56295/agj5737","url":null,"abstract":"Challenges in the extraction and use of earth resources and spaces are encountered given a growing worldwide population, rising infrastructures development, and widespread climate change. In Australia, mining and construction are two major bases for economic growth while both being traditional hazardous and heavy industries. A nation-wide infrastructure upgrade featuring large-scale underground development is underway, the geological uncertainties and localisation difficulties of already laid infrastructure are associated with challenges not seen in building construction. A safer and competent subterranean transport solution is yet proposed in the context of sustainable developments. In light of this, geotechnical analysis as a fundamental subject for developing and maintaining safe and sustainable use of underground space has huge potential to be undertaken more intuitively considering the advancements in information management and visualisation. The PhD work examines the state-of-the-art applications, limitations and future opportunities of Building Information Modelling (BIM) and other computational techniques in the digitisation of tunnelling and underground construction. The visualisation and interoperability facilitated by data-driven processes are especially important to underground construction that engages interdisciplinary and multi-environment interaction.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45910765","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}
Amir Tophel, Jeffrey M. Walker, Ye Lu, J. Kodikara
The measurement of density or void ratio during the compaction of geomaterials (soils and unbound granular materials) in the field during road construction is essential for superior performance. The specifications adopted by the road authorities worldwide are exclusively based on density. However, estimating density evolution proximally or non-destructively is challenging. Conventional field-based density measurement techniques are hazardous, slow to use and are point-based measurements. This study developed a novel methodology to estimate the density of geomaterials non-destructively in real-time during the compaction process. The methodology included measuring the surface deformation using Light Detection and Ranging (LiDAR) systems attached to rollers and developing physics-based 1-Dimensional and machine learning (ML) based constitutive models to relate the measured parameters to the density. The developed methodology was validated in an indoor environment where a large soil box (dimensions: 7.5 m×4 m×0.8 m) was fabricated and a well-graded sand in 5 layers of 100 mm was compacted using a 1.5-tonne instrumented roller. The measurement of deformation provided an opportunity to estimate the density in real-time. The estimated density using 1-D model and a ML based classification model had an error of 20% and 16% respectively when compared to density measured from Nuclear Density Gauge (NDG). This novel instrumentation allowed the density to be measured during compaction with high accuracy, which presents an unprecedented advantage over other conventional approaches, which are intrusive and pointwise, thereby ensuring that the road will be constructed expediently and will function satisfactorily, minimising the occurrence of premature failures. The continual measurement of density during compaction will also facilitate maintaining uniformity of the density, thereby reducing the potential for excessive differential deformations.
{"title":"Proximal Sensing of Density During Soil Compaction by Instrumented Roller","authors":"Amir Tophel, Jeffrey M. Walker, Ye Lu, J. Kodikara","doi":"10.56295/agj5739","DOIUrl":"https://doi.org/10.56295/agj5739","url":null,"abstract":"The measurement of density or void ratio during the compaction of geomaterials (soils and unbound granular materials) in the field during road construction is essential for superior performance. The specifications adopted by the road authorities worldwide are exclusively based on density. However, estimating density evolution proximally or non-destructively is challenging. Conventional field-based density measurement techniques are hazardous, slow to use and are point-based measurements. This study developed a novel methodology to estimate the density of geomaterials non-destructively in real-time during the compaction process. The methodology included measuring the surface deformation using Light Detection and Ranging (LiDAR) systems attached to rollers and developing physics-based 1-Dimensional and machine learning (ML) based constitutive models to relate the measured parameters to the density. The developed methodology was validated in an indoor environment where a large soil box (dimensions: 7.5 m×4 m×0.8 m) was fabricated and a well-graded sand in 5 layers of 100 mm was compacted using a 1.5-tonne instrumented roller. The measurement of deformation provided an opportunity to estimate the density in real-time. The estimated density using 1-D model and a ML based classification model had an error of 20% and 16% respectively when compared to density measured from Nuclear Density Gauge (NDG). This novel instrumentation allowed the density to be measured during compaction with high accuracy, which presents an unprecedented advantage over other conventional approaches, which are intrusive and pointwise, thereby ensuring that the road will be constructed expediently and will function satisfactorily, minimising the occurrence of premature failures. The continual measurement of density during compaction will also facilitate maintaining uniformity of the density, thereby reducing the potential for excessive differential deformations.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44348196","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}
Luis-Fernando Contreras, Sandra Linero-Molina, J. Dixon
The evaluation of the shear strength of waste rock is required for the verification of the stability of high waste dumps, especially those that reach hundreds of meters in height. Mine waste rock material in open pit mining contains particles of metric scale which precludes the utilisation of commercial laboratory testing equipment. To overcome testing limitations, the shear strength of waste rock is frequently estimated using the empirical criterion of Barton-Kjærnsli. This criterion takes into consideration the nonlinearity of the shear strength envelope, characterising the behaviour of very coarse granular materials submitted to high loads. In the criterion, a stress-dependent structural component of the shear strength is parametrised with the equivalent roughness (R) and equivalent strength (S) and the structural component is added to the basic friction angle (φb) of the parental rock to determine the shear strength of the waste rock material. This paper demonstrates the use of Bayesian inference to determine the best set of parameters φb, R and S that satisfied both: large-scale laboratory testing results characterising a waste rock material, and reconciliation data from observations of stability of the waste dumps. The methodology allows the estimation of project-specific model parameters that honour both, laboratory data and site performance information. This objective is achieved through the estimation of correction factors to downgrade the strength from laboratory to field scale.
{"title":"Bayesian Approach To Improve The Confidence Of The Estimation Of The Shear Strength Of Coarse Mine Waste Using Barton’s Empirical Criterion","authors":"Luis-Fernando Contreras, Sandra Linero-Molina, J. Dixon","doi":"10.56295/agj5728","DOIUrl":"https://doi.org/10.56295/agj5728","url":null,"abstract":"The evaluation of the shear strength of waste rock is required for the verification of the stability of high waste dumps, especially those that reach hundreds of meters in height. Mine waste rock material in open pit mining contains particles of metric scale which precludes the utilisation of commercial laboratory testing equipment. To overcome testing limitations, the shear strength of waste rock is frequently estimated using the empirical criterion of Barton-Kjærnsli. This criterion takes into consideration the nonlinearity of the shear strength envelope, characterising the behaviour of very coarse granular materials submitted to high loads. In the criterion, a stress-dependent structural component of the shear strength is parametrised with the equivalent roughness (R) and equivalent strength (S) and the structural component is added to the basic friction angle (φb) of the parental rock to determine the shear strength of the waste rock material. This paper demonstrates the use of Bayesian inference to determine the best set of parameters φb, R and S that satisfied both: large-scale laboratory testing results characterising a waste rock material, and reconciliation data from observations of stability of the waste dumps. The methodology allows the estimation of project-specific model parameters that honour both, laboratory data and site performance information. This objective is achieved through the estimation of correction factors to downgrade the strength from laboratory to field scale.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48595605","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}
Arsham Mazaheri, M. Hajiazizi, R. Orense, M. Veiskarami, M. Biglari
This paper attempts to investigate the concept of forces acting on sheet pile installed in sliding slope. A new analytical formulation is proposed to reinforce the sliding slope. The equilibrium equation is formulated, and a new relationship is proposed to calculate the force exerted on the sheet pile. When the slope is stable the minimum force and moment are exerted on the sheet pile; however, when the slope starts to move the moment and force exerted on the sheet pile are increased. A reduction of 5 kPa in cohesion increases the force exerted on the sheet pile by about 180 kN/m. By reducing the friction angle by 5 degrees, the force exerted on the sheet pile is increased by about 50 kN/m. The proposed analytical formulation is shown good agreement with numerical analysis.
{"title":"Prediction Of Force Exerted On Stabilizing Sheet Piles In The Sliding Slope","authors":"Arsham Mazaheri, M. Hajiazizi, R. Orense, M. Veiskarami, M. Biglari","doi":"10.56295/agj5727","DOIUrl":"https://doi.org/10.56295/agj5727","url":null,"abstract":"This paper attempts to investigate the concept of forces acting on sheet pile installed in sliding slope. A new analytical formulation is proposed to reinforce the sliding slope. The equilibrium equation is formulated, and a new relationship is proposed to calculate the force exerted on the sheet pile. When the slope is stable the minimum force and moment are exerted on the sheet pile; however, when the slope starts to move the moment and force exerted on the sheet pile are increased. A reduction of 5 kPa in cohesion increases the force exerted on the sheet pile by about 180 kN/m. By reducing the friction angle by 5 degrees, the force exerted on the sheet pile is increased by about 50 kN/m. The proposed analytical formulation is shown good agreement with numerical analysis.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43940531","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}
Embankments rested on soft soils reinforced with stone columns cannot provide enough support. In such soils, to increase their bearing capacity, pervious concrete can be applied to upper portion of the stone column forms a composite column to restrain bulging collapse. Pervious concrete is a type of concrete made without adding fine aggregate and having permeability comparable with stone column materials. The current research work carried out to study the behaviour of embankment rested on composite column through a parametric study using finite element analysis. The parameters; soft clay elastic modulus, embankment fill elastic modulus, stone column material elastic modulus, pervious concrete column elastic modulus, spacing of column, length of pervious concrete column in composite column, permeability of soft clay, and construction rate are considered for the parametric study. The influence of these parameters are compared and rated in terms of the degree of importance.
{"title":"Finite Element Modelling Of An Embankment Seated On Pervious Concrete-Stone Composite Column","authors":"J. Patel, Chetan G Solanki, YK Tandel, Bg Patel","doi":"10.56295/agj5722","DOIUrl":"https://doi.org/10.56295/agj5722","url":null,"abstract":"Embankments rested on soft soils reinforced with stone columns cannot provide enough support. In such soils, to increase their bearing capacity, pervious concrete can be applied to upper portion of the stone column forms a composite column to restrain bulging collapse. Pervious concrete is a type of concrete made without adding fine aggregate and having permeability comparable with stone column materials. The current research work carried out to study the behaviour of embankment rested on composite column through a parametric study using finite element analysis. The parameters; soft clay elastic modulus, embankment fill elastic modulus, stone column material elastic modulus, pervious concrete column elastic modulus, spacing of column, length of pervious concrete column in composite column, permeability of soft clay, and construction rate are considered for the parametric study. The influence of these parameters are compared and rated in terms of the degree of importance.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42859681","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 original paper, Rallings (2018), presented a rudimentary behavioural model of the response of unbound granular pavements (UGPs), ones that are founded on compacted clay subgrades, to passages of single wheel loads. The following amends and expands the original model and includes new terms and concepts. The proposed model is based on the assumption that elevated subgrade shear strains in conjunction with a strain-controlled mechanism disturb the fabric of the overlying granular materials (OGM) causing reductions in their stiffness and in the UGP’s load carrying capacity, essentially its ability to maintain its surface shape. It is proposed that short term falls in the subgrade shear strength and/or increases in the frequency of the heaviest loads within the wheel load spectrum are the common major contributors to the degradation of a UGP’s load carrying capacity. The proposed model provides a direct and simple means to predict the response of a UGP to load passages, allowing designers and asset managers alike to distinguish between those wheel loads that pose a potential threat to the UGP from those that do not.
{"title":"Unbound Granular Pavements; Design With Understanding : A Revision And Extension","authors":"R. Rallings","doi":"10.56295/agj5726","DOIUrl":"https://doi.org/10.56295/agj5726","url":null,"abstract":"The original paper, Rallings (2018), presented a rudimentary behavioural model of the response of unbound granular pavements (UGPs), ones that are founded on compacted clay subgrades, to passages of single wheel loads. The following amends and expands the original model and includes new terms and concepts. The proposed model is based on the assumption that elevated subgrade shear strains in conjunction with a strain-controlled mechanism disturb the fabric of the overlying granular materials (OGM) causing reductions in their stiffness and in the UGP’s load carrying capacity, essentially its ability to maintain its surface shape. It is proposed that short term falls in the subgrade shear strength and/or increases in the frequency of the heaviest loads within the wheel load spectrum are the common major contributors to the degradation of a UGP’s load carrying capacity. The proposed model provides a direct and simple means to predict the response of a UGP to load passages, allowing designers and asset managers alike to distinguish between those wheel loads that pose a potential threat to the UGP from those that do not.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46627533","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}
D. Guccione, O. Buzzi, K. Thoeni, A. Giacomini, S. Fityus
Rockfall fragmentation is a common and very complex phenomenon that is still inadequately understood and rarely modelled. When falling rock blocks break upon impact, their shape and size change and the kinetic energy is distributed amongst fragments. To efficiently design mitigation measures, it is necessary to adequately account for fragmentation when modelling rockfall trajectories. To do so, a better understanding of the fragmentation process, its occurrence and its likely outcomes is needed. The authors have recently proposed a novel model which can predict the survival probability (SP) of brittle spheres upon impact from the statistical distribution of material parameters, obtained by standard quasi- static tests (Brazilian tests and unconfined compression tests). The model predicts two Weibull parameters (shape parameter -m- and scale parameter – critical kinetic energy) that are used to define the SP. The model is based on theoretically-derived (from Hertzian contact theory) conversion factors used to transform the critical work required to fail disc samples in quasi-static indirect tension into the critical kinetic energy to cause failure of spheres at impact in vertical drop tests. The objective of this paper is to provide some practical insights into this model in relation of the analysis of the Brazilian test results and the number of Brazilian tests required to achieve an acceptable prediction. A first analysis highlights the importance of distribution of forces required to break the specimens in Brazilian tests and a common statistical based outlier removal methodology was applied to reduce the experimental error associated with the operator. After eliminating the outlier data, the quality of prediction is improved and, in particular, the influence of the specimen diameter used in Brazilian compressions to derive the model input parameter is significantly reduced. This latter point implies that the size effect is adequately captured. The second analysis reveals the highest variability for batches with low number of tests and a progressive reduction as the number of sampled test increases. Based on these results, it is suggested to use at least 30 Brazilian tests and remove outliers using the simple statistical approach presented in the paper.
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