It is my great pleasure and honour to introduce this issue of Australian Geomechanics. Following the resignation of previous Editor Bre-Anne Sainsbury, I offered to take on the Interim Editor role from the June 2023 issue to ensure continuity of the publication. The task duration has extended and based on the work completed to produce the latter three issues of the 2023 calendar year, this brief note presents some basic journal analytics, discusses current challenges facing Australian Geomechanics and aims to encourage the membership to prepare submissions for the benefit of the readership and the wider Australian geomechanics community. The sections about challenges and initiatives include references to discussions and brainstorming exercises held during my time at the AGS National Committee (2013-2019) and input from past Chairs and committee members during that period is acknowledged.
{"title":"Australian Geomechanics – State of the Journal","authors":"Hugo Acosta-Martinez","doi":"10.56295/agj5911","DOIUrl":"https://doi.org/10.56295/agj5911","url":null,"abstract":"It is my great pleasure and honour to introduce this issue of Australian Geomechanics. Following the resignation of previous Editor Bre-Anne Sainsbury, I offered to take on the Interim Editor role from the June 2023 issue to ensure continuity of the publication. The task duration has extended and based on the work completed to produce the latter three issues of the 2023 calendar year, this brief note presents some basic journal analytics, discusses current challenges facing Australian Geomechanics and aims to encourage the membership to prepare submissions for the benefit of the readership and the wider Australian geomechanics community. The sections about challenges and initiatives include references to discussions and brainstorming exercises held during my time at the AGS National Committee (2013-2019) and input from past Chairs and committee members during that period is acknowledged.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140089018","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}
Relationships between the shrink-swell index and other clay tests, such as Atterberg limits have been investigated by others however, there is not any available information for the Wagga Wagga region in NSW Australia. This study’s objective is to establish some relationships between the shrink-swell index and Atterberg limits of the soils in the Wagga Wagga region. A total of 27 samples at different locations and depths was tested for shrink-swell index, linear shrinkage, liquid limit, plastic limit, plasticity index and soil particle size distribution, using Australian Standard test methods. The results and data analysis indicated that shrink-swell index correlated with Atterberg limits. The shrink-swell index can be estimated based on a single Atterberg limit test or the combination of linear shrinkage + liquid limit and linear shrinkage + plasticity index. In conclusion, linear shrinkage and liquid limit are the reasonable prediction factors for the estimation of shrink-swell index for the soils in the Wagga Wagga region.
{"title":"Can the shrink-swell index be predicted in the Wagga Wagga region based on Atterberg limits?","authors":"Hoang Han Nguyen, David McMahon","doi":"10.56295/agj5916","DOIUrl":"https://doi.org/10.56295/agj5916","url":null,"abstract":"Relationships between the shrink-swell index and other clay tests, such as Atterberg limits have been investigated by others however, there is not any available information for the Wagga Wagga region in NSW Australia. This study’s objective is to establish some relationships between the shrink-swell index and Atterberg limits of the soils in the Wagga Wagga region. A total of 27 samples at different locations and depths was tested for shrink-swell index, linear shrinkage, liquid limit, plastic limit, plasticity index and soil particle size distribution, using Australian Standard test methods. The results and data analysis indicated that shrink-swell index correlated with Atterberg limits. The shrink-swell index can be estimated based on a single Atterberg limit test or the combination of linear shrinkage + liquid limit and linear shrinkage + plasticity index. In conclusion, linear shrinkage and liquid limit are the reasonable prediction factors for the estimation of shrink-swell index for the soils in the Wagga Wagga region.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140082723","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}
Packer testing allows estimation of the hydraulic conductivity of the ground through analysis of an induced flow rate into the ground under various controlled water pressures. Consideration of the physical and practical limits of injecting and monitoring such flows and pressures is used to determine the limits of hydraulic conductivity that can reasonably be estimated from packer tests. A design chart is presented based on these practical limits and consideration of the fundamental mathematics underpinning packer test interpretation. The chart is proposed as a useful reference when planning or reviewing field testing programs.
{"title":"The practical limits of packer testing","authors":"Steven Pells","doi":"10.56295/agj5912","DOIUrl":"https://doi.org/10.56295/agj5912","url":null,"abstract":"Packer testing allows estimation of the hydraulic conductivity of the ground through analysis of an induced flow rate into the ground under various controlled water pressures. Consideration of the physical and practical limits of injecting and monitoring such flows and pressures is used to determine the limits of hydraulic conductivity that can reasonably be estimated from packer tests. A design chart is presented based on these practical limits and consideration of the fundamental mathematics underpinning packer test interpretation. The chart is proposed as a useful reference when planning or reviewing field testing programs.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140091101","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}
Giovanny Alvarado-Gutierrez, Somaye Sadeghian, Yang Dong
Excavations change the stress state of the in-situ ground. The altered stress state causes lateral and vertical displacement in the buildings and structures adjacent to the excavation. In areas like the Sydney region, tectonic locked-in horizontal stresses at shallow depth exceed the vertical stress and the high in-situ horizontal stresses cause possibility of excavation-induced displacement in good quality rocks (e.g., Hawkesbury Sandstone Class I, II, and III). This paper estimates the magnitude and shape of the excavation-induced displacement trough along the excavation edge in Hawkesbury Sandstone. A parametric study was undertaken using three-dimensional finite element analysis to estimate the maximum lateral excavation-induced displacement as well as the lateral displacement trough as a function of the ground type, excavation depth and width, and principal in-situ stress orientation. The results were verified by comparing with monitoring results published for Sydney Sandstone.
挖掘工程会改变原地地面的应力状态。应力状态的改变会导致挖掘区附近的建筑物和结构发生横向和纵向位移。在悉尼地区等地区，浅层的构造锁定水平应力超过了垂直应力，高原位水平应力导致优质岩石（如霍克斯伯里砂岩 I 级、II 级和 III 级）可能出现挖掘引起的位移。本文估算了霍克斯伯里砂岩开挖边缘开挖诱发位移槽的大小和形状。利用三维有限元分析进行了参数研究，以估算挖掘引起的最大横向位移，以及横向位移槽与地层类型、挖掘深度和宽度以及原位主应力方向的函数关系。研究结果与悉尼砂岩的监测结果进行了对比验证。
{"title":"Simplified excavation-induced lateral displacement assessment in Sydney area","authors":"Giovanny Alvarado-Gutierrez, Somaye Sadeghian, Yang Dong","doi":"10.56295/agj5913","DOIUrl":"https://doi.org/10.56295/agj5913","url":null,"abstract":"Excavations change the stress state of the in-situ ground. The altered stress state causes lateral and vertical displacement in the buildings and structures adjacent to the excavation. In areas like the Sydney region, tectonic locked-in horizontal stresses at shallow depth exceed the vertical stress and the high in-situ horizontal stresses cause possibility of excavation-induced displacement in good quality rocks (e.g., Hawkesbury Sandstone Class I, II, and III). This paper estimates the magnitude and shape of the excavation-induced displacement trough along the excavation edge in Hawkesbury Sandstone. A parametric study was undertaken using three-dimensional finite element analysis to estimate the maximum lateral excavation-induced displacement as well as the lateral displacement trough as a function of the ground type, excavation depth and width, and principal in-situ stress orientation. The results were verified by comparing with monitoring results published for Sydney Sandstone.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140084458","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 Queensland Geotechnical Database (QGD; qgd.org.au) was launched in October 2017 with the aim of consolidating primarily tax and toll-payer subsidised geotechnical investigation logs into an open platform. The QGD was influenced by public geotechnical databases in the United Kingdom and New Zealand, and the work of Robert Leggett in Canada as summarised in ‘Cities and Geology’ (1973). As of October 2023, the QGD includes over 3100 geotechnical investigation logs authored by over 10 public and private entities, dating back to 1966. It also includes national geological mapping and links to over 400 technical papers related to sites in Australia. This paper summarises the formation of the QGD, which emerged from the Queensland Chapter of the Australian Geomechanics Society (AGS) and originated from a personal database converted to an open format with hosting support from The Open Data Institute Australia. The QGD was later transferred to The University of Queensland and continues there in support of their Sustainable Infrastructure Research Hub (UQ SIRH). The paper explores the evolution of its formation, the legal framework in Australia regarding investigation log ownership, and the licensing scheme adopted for the database. It outlines the technical features and intended practicality of the database, and its alignment with the objectives of the UQ SIRH. The paper concludes with an outline of opportunities for conversion to a nationalised Australian Geotechnical Database and its usage for educational purposes.
{"title":"The Queensland geotechnical database","authors":"Timothy Thompson, Jared Priddle, Jurij Karlovsek","doi":"10.56295/agj5915","DOIUrl":"https://doi.org/10.56295/agj5915","url":null,"abstract":"The Queensland Geotechnical Database (QGD; qgd.org.au) was launched in October 2017 with the aim of consolidating primarily tax and toll-payer subsidised geotechnical investigation logs into an open platform. The QGD was influenced by public geotechnical databases in the United Kingdom and New Zealand, and the work of Robert Leggett in Canada as summarised in ‘Cities and Geology’ (1973). As of October 2023, the QGD includes over 3100 geotechnical investigation logs authored by over 10 public and private entities, dating back to 1966. It also includes national geological mapping and links to over 400 technical papers related to sites in Australia. This paper summarises the formation of the QGD, which emerged from the Queensland Chapter of the Australian Geomechanics Society (AGS) and originated from a personal database converted to an open format with hosting support from The Open Data Institute Australia. The QGD was later transferred to The University of Queensland and continues there in support of their Sustainable Infrastructure Research Hub (UQ SIRH). The paper explores the evolution of its formation, the legal framework in Australia regarding investigation log ownership, and the licensing scheme adopted for the database. It outlines the technical features and intended practicality of the database, and its alignment with the objectives of the UQ SIRH. The paper concludes with an outline of opportunities for conversion to a nationalised Australian Geotechnical Database and its usage for educational purposes.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140084264","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}
Within the large, open cut, iron ore mines of the Pilbara region of Western Australia, defect shear strengths often control the slope design where bedding dips shallowly to moderately out of the pit slope. The presence of metre to decametre scale open folding or waviness in these units can contribute to the friction angle of bedding shear strengths, potentially allowing for steeper slope angles and improved economics for the deposit. Traditionally, waviness affecting defect shear strength is assessed from surface mapping, bench mapping or qualitatively from observations in core. Surface mapping of bedrock is often not possible due to detrital cover or a lack of suitable outcrop, while bench mapping is inherently conducted perpendicular to the direction of sliding risk. The use of downhole data from boreholes drilled into the slopes circumvents these issues. The method presented here involves assessing characteristic downhole wavelength, inter-limb angle and amplitude of folding from defect orientation data interpreted from borehole televiewer imaging. The downhole wavelength and defect orientations are transformed to a true down-dip wavelength, dilation angle, and estimated amplitude in the direction of sliding risk. The calculation of down-dip wavelength is critical for assessing the applicability of the associated dilation angle to the scale of the slope and failure mechanism in question. The adoption of defect shear strengths that include a waviness contribution to the friction angle allows for implementation of steeper slope angles in structurally controlled slopes.
{"title":"Assessing the geometry of defect waviness from borehole data","authors":"Duncan Noble","doi":"10.56295/agj5914","DOIUrl":"https://doi.org/10.56295/agj5914","url":null,"abstract":"Within the large, open cut, iron ore mines of the Pilbara region of Western Australia, defect shear strengths often control the slope design where bedding dips shallowly to moderately out of the pit slope. The presence of metre to decametre scale open folding or waviness in these units can contribute to the friction angle of bedding shear strengths, potentially allowing for steeper slope angles and improved economics for the deposit. Traditionally, waviness affecting defect shear strength is assessed from surface mapping, bench mapping or qualitatively from observations in core. Surface mapping of bedrock is often not possible due to detrital cover or a lack of suitable outcrop, while bench mapping is inherently conducted perpendicular to the direction of sliding risk. The use of downhole data from boreholes drilled into the slopes circumvents these issues. The method presented here involves assessing characteristic downhole wavelength, inter-limb angle and amplitude of folding from defect orientation data interpreted from borehole televiewer imaging. The downhole wavelength and defect orientations are transformed to a true down-dip wavelength, dilation angle, and estimated amplitude in the direction of sliding risk. The calculation of down-dip wavelength is critical for assessing the applicability of the associated dilation angle to the scale of the slope and failure mechanism in question. The adoption of defect shear strengths that include a waviness contribution to the friction angle allows for implementation of steeper slope angles in structurally controlled slopes.","PeriodicalId":43619,"journal":{"name":"Australian Geomechanics Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140089457","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 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":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"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":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"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":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"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":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"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}
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