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":" ","pages":""},"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}
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":" ","pages":""},"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":" ","pages":""},"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.
{"title":"Practical Considerations For The Application Of A Survival Probability Model For Rockfall","authors":"D. Guccione, O. Buzzi, K. Thoeni, A. Giacomini, S. Fityus","doi":"10.56295/agj5725","DOIUrl":"https://doi.org/10.56295/agj5725","url":null,"abstract":"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.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":" ","pages":""},"PeriodicalIF":0.2,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47412355","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}
This paper aims to provide guidance on a process for the design of bridge foundations. It sets out a brief explanation of bridge terminology, and afterwards discusses aspects of the geotechnical investigation, foundation design, and construction specification for bridges. It is intended to assist engineers who may not be familiar with bridge design in gaining a working knowledge of the basic design principles and requirements. It is not intended as a detailed step-by-step procedure for foundation design itself, but rather as a framework for a systematic process of design. Among the aspects that are emphasized are the process of assessment of geotechnical design parameters, and the means by which the outputs from geotechnical analyses can be most effectively communicated to others involved in the design process, especially the structural engineers.
{"title":"A Practical Approach To Bridge Foundation Design","authors":"H. Poulos, J. Ameratunga","doi":"10.56295/agj5723","DOIUrl":"https://doi.org/10.56295/agj5723","url":null,"abstract":"This paper aims to provide guidance on a process for the design of bridge foundations. It sets out a brief explanation of bridge terminology, and afterwards discusses aspects of the geotechnical investigation, foundation design, and construction specification for bridges. It is intended to assist engineers who may not be familiar with bridge design in gaining a working knowledge of the basic design principles and requirements. It is not intended as a detailed step-by-step procedure for foundation design itself, but rather as a framework for a systematic process of design. Among the aspects that are emphasized are the process of assessment of geotechnical design parameters, and the means by which the outputs from geotechnical analyses can be most effectively communicated to others involved in the design process, especially the structural engineers.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":" ","pages":""},"PeriodicalIF":0.2,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49336820","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 study aims to develop proposed predictive formulas for determining the unconfined compression strength (UCS) of cement/lime stabilized Queensland soil based on Multi-Gene Genetic Programming (MGGP) and Artificial Neural Network (ANN). The models evaluate the effect of three independent variables, including the binder type (cement and lime), the binder content, and the curing time, on the UCS of the stabilized soil. The results show that the selected optimal MGGP and ANN models can predict the target values with high correlation coefficients (R-value approximately of 0.992 and 0.998, respectively), and low errors (e.g., RMSE and MAE). The sensitivity analysis of the MGGP and ANN models provide the same results, in which the curing time has the greatest influence on the UCS value, followed by the binder content and binder type. The performances of the MGGP and ANN models are compared based on statistical parameters, several external criteria, and distribution properties. The study finds that both models show their generalization capabilities with robust, powerful, and accurate prediction ability; however, the ANN model slightly outperforms the MGGP model. The proposed predictive equations formulated from the selected optimal MGGP and ANN models could help engineers and consultants to choose the suitable binder and the reasonable amount of binder in the pre-planning and pre-design period.
{"title":"Intelligent Prediction Models For UCS Of Cement/Lime Stabilized QLD Soil","authors":"V. Pham","doi":"10.56295/agj5721","DOIUrl":"https://doi.org/10.56295/agj5721","url":null,"abstract":"The study aims to develop proposed predictive formulas for determining the unconfined compression strength (UCS) of cement/lime stabilized Queensland soil based on Multi-Gene Genetic Programming (MGGP) and Artificial Neural Network (ANN). The models evaluate the effect of three independent variables, including the binder type (cement and lime), the binder content, and the curing time, on the UCS of the stabilized soil. The results show that the selected optimal MGGP and ANN models can predict the target values with high correlation coefficients (R-value approximately of 0.992 and 0.998, respectively), and low errors (e.g., RMSE and MAE). The sensitivity analysis of the MGGP and ANN models provide the same results, in which the curing time has the greatest influence on the UCS value, followed by the binder content and binder type. The performances of the MGGP and ANN models are compared based on statistical parameters, several external criteria, and distribution properties. The study finds that both models show their generalization capabilities with robust, powerful, and accurate prediction ability; however, the ANN model slightly outperforms the MGGP model. The proposed predictive equations formulated from the selected optimal MGGP and ANN models could help engineers and consultants to choose the suitable binder and the reasonable amount of binder in the pre-planning and pre-design period.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":" ","pages":""},"PeriodicalIF":0.2,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48059405","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}
This paper presents a case study of geotechnical design and construction challenges of bridge foundations and approaches in a hilly granite formation in northern New South Wales, Australia. Firstly, the geological formation and existing cut slope conditions which have high risks of rock fall is described. The detailed design was based on the available geotechnical information and assumed construction methodology. Reinforced concrete cantilever retaining walls founded on mass concrete were adopted for the bridge southern approach to resolve constructability issues over hilly terrain. Slope treatments using a rock fall fence together with individual boulder stabilisation or removal were also considered. It was found during construction that the actual ground conditions were different to that originally inferred and modifications to pad footing designs were deemed necessary. Additional investigations were undertaken, and the subsurface ground models updated to inform the revised design. For the northern bridge abutment foundation, a piled foundation was introduced to optimise the design with due consideration of temporary piling platform and access along a new geotextile reinforced approach embankment. The revised design was developed in close collaboration with the Contractor and the Principal. The foundation design of Pier 2 was revised using micro-piles to address the presence of a weak rock layer intrusion. In the end, key lessons learnt from this challenging project have been summarised for future project references.
{"title":"Geotechnical Challenges And Lessons Learnt From Bolivia Hill Upgrade Project","authors":"Qj Yang, J. Dane","doi":"10.56295/agj5724","DOIUrl":"https://doi.org/10.56295/agj5724","url":null,"abstract":"This paper presents a case study of geotechnical design and construction challenges of bridge foundations and approaches in a hilly granite formation in northern New South Wales, Australia. Firstly, the geological formation and existing cut slope conditions which have high risks of rock fall is described. The detailed design was based on the available geotechnical information and assumed construction methodology. Reinforced concrete cantilever retaining walls founded on mass concrete were adopted for the bridge southern approach to resolve constructability issues over hilly terrain. Slope treatments using a rock fall fence together with individual boulder stabilisation or removal were also considered. It was found during construction that the actual ground conditions were different to that originally inferred and modifications to pad footing designs were deemed necessary. Additional investigations were undertaken, and the subsurface ground models updated to inform the revised design. For the northern bridge abutment foundation, a piled foundation was introduced to optimise the design with due consideration of temporary piling platform and access along a new geotextile reinforced approach embankment. The revised design was developed in close collaboration with the Contractor and the Principal. The foundation design of Pier 2 was revised using micro-piles to address the presence of a weak rock layer intrusion. In the end, key lessons learnt from this challenging project have been summarised for future project references.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":" ","pages":""},"PeriodicalIF":0.2,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43481939","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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