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Analytical investigations of in situ stress inversion from borehole breakout geometries

Journal of Rock Mechanics and Geotechnical Engineering 2024年第7期16卷 2375-2387页

作者： Zizhuo Xiang Taehyun Moon joung oh Guangyao Si Ismet Canbulat School of Minerals and Energy Resources Engineering University of New South WalesSydneyNSW2052Australia HNTB Corporation 3505th Ave.58th FloorNew YorkNY10118USA

This study aims to investigate the feasibility of deriving in situ horizontal stresses from the breakout width and depth using the analytical ***-three breakout data with different borehole sizes were collected and three failure criteria were *** on the Kirsch equations,relatively accurate major horizontal stress(sH)estimations from known minor horizontal stress(sh)were achieved with percentage errors ranging from 0.33%to 44.08%using the breakout *** Mogi-Coulomb failure criterion(average error:13.1%)outperformed modified Wiebols-Cook(average error:19.09%)and modified Lade(average error:18.09%)failure ***,none of the tested constitutive models could yield reasonable sh predictions from known sH using the same approach due to the analytical expression of the redistributed stress and the nature of the constitutive *** consideration of this issue,the horizontal stress ratio(sH/sh)is suggested as an alternative input,which could estimate both sH and sh with the same level of ***,the estimation accuracies for both large-scale and laboratory-scale breakouts are comparable,suggesting the applicability of this approach across different breakout *** breakout depth,conformal mapping and complex variable method were used to calculate the stress concentration around the breakout tip,allowing the expression of redistributed stresses using binomials composed of sH and ***,analysis of the breakout depth stabilisation mechanism indicates that additional parameters are required to utilise normalised breakout depth for stress estimation compared to breakout *** parameters are challenging to obtain,especially under field conditions,meaning utilising normalised breakout depth analytically in practical applications faces significant challenges and remains infeasible at this ***,the normalised breakout depth should still be considered a critical input for any empirical and statistical stres

关键词： Borehole failure In situ stress estimation In situ horizontal stress ratio Conformal mapping Complex variable method Breakout stabilisation

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Assessments of the effects of various fracture surface morphology on single fracture flow: A review

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International Journal of Mining Science and Technology 2023年第1期33卷 1-29页

作者： Min Gao Chengguo Zhang joung oh School of Minerals and Energy Resources Engineering University of New South WalesSydney NSW 2052Australia

Natural rock joint permeability deviates from the classic fluid flow governing equations due to the inher-ent fracture surface roughness(i.e.,contact points,spatial correlation,matching,varying aperture,iso-lated voids,infilling material,tortuosity and channellings)and engineering disturbance such as *** improve the accuracy of fracture permeability evaluation,many efforts have been made in analytical,experimental,and numerical *** study reviews the modified mathematical gov-erning equations of fluid flow and classifies them based on different influencing factors,such as friction factor,aperture,tortuosity,inertia,and various in situ stress *** experimental and simulation techniques for the coupled normal-and shear-stress flow problems were assessed,and their advantages and disadvantages were also ***,different surface roughness descriptions and their impacts on mechanical and hydraulic behaviours were discussed,followed by the potential research directions for fracture flow problems.

关键词： Surface roughness Single fracture Nonlinear flow Coupled hydromechanical(HM)behaviours

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Methods applied in Australian industry to evaluate coal mine slope stability

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International Journal of Mining Science and Technology 2020年第2期30卷 151-155页

作者： Alison McQuillan Ismet Canbulat joung oh School of Minerals and Energy Resources Engineering UNSW SydneyAustralia

Strata failure is a principal hazard in open cut coal mining as it has the potential to cause multiple *** to the excavation of any slope,a geotechnical assessment should review the likely slope performance,including the risk of slope *** to manage this risk to an acceptable level should accompany the geotechnical analysis.A survey of 43 practising geotechnical engineers indicated that kinematic and 2D limit equilibrium analyses were the methods most commonly applied to analyse excavated slope *** these methods are well established and widely applied in the broad rock engineering disciplines(***,hard rock),a recent review of over 60 slope failures suggests these methods have limited suitability for modelling the complex failure mechanisms observed in excavated coal mine *** techniques do not adequately capture the rock mass component of excavated slope failure and do not provide a geospatial location of potential failure,while 2D limit equilibrium techniques do not adequately capture the 3D mechanisms of excavated slope *** which do consider the 3D mechanisms of slope failure are summarized for industry consideration and application.

关键词： Slope stability 2D 3D Open cut coal mine Limit equilibrium

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New risk assessment methodology for coal mine excavated slopes

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International Journal of Mining Science and Technology 2018年第4期28卷 581-590页

作者： Alison McQuillan Ismet Canbulat Dan Payne joung oh School of Minerals and Energy Resources Engineering UNSW SydneySydney 2052Australia BHP Billiton Coal Level 11480 Queen StBrisbaneQueensland 4000Australia

This paper presents a new risk assessment methodology for coal mine excavated slopes. This new empirical-statistical *** assessment m. ethodology （SSAM! is intended for use by geotechnical engineers at both the design review and operational stages of a mine＇s life to categonse the risk of an excavated coal mine slope. A likelihood of failure is determined using a new slope stability classification system for excavated coal mine slopes developed using a database of 119 intact and failed case studies sourced from open cut coal mines in Australia. Consequence of failure is based on slope height and stand-off distance at the toe of the excavated slope. Results are presented in a new risk matrix, with slope risk being divided into low, medium and high categories. The SSAM is put forward as a new risk assess- ment methodology to assess the potential for, and consequence of, excavated coal mine slope failure. Unlike existing classification systems, assumptions about the likely failure mode or mechanism are not required. Instead, the SSAM applies an approach which compares the conditions present within the exca- vated slope face, with the known past performance of slopes with similar geotechnical and geometrical conditions, to estimate the slope＇s propensity for failure. The SSAM is novel in that it considers the depo- sitional history of strata in an excavated slope and how this sequence affects slope stability. It is further novel in that it does not require explicit measurements of intact rock, rock mass and/or defect strength to rapidly calculate a slope＇s likelihood of failure and overall risk. Ratings can be determined entirely from visual observations of the excavated slope face. The new SSAM is designed to be used in conjunction with existing slope stability assessment tools.

关键词： Risk assessment Slope stability Open cut coal mine Excavated slope Likelihood of failure

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A review of cavability evaluation in longwall top coal caving

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International Journal of Mining Science and Technology 2017年第6期27卷 907-915页

作者： Tien Dung Le Rudrajit Mitra joung oh Bruce Hebblewhite School of Mining Engineering The University of New South Wales Sydney NSW 2052 Australia

Longwall Top Coal Caving has been considered as one of the most effective technologies for the extraction of underground thick coal seams. A large number of studies on the applicability of Longwall Top Coal Caving into new mine sites have linked the success of its application to the geo mechanical understanding of the cavability of the top coal. The paper aims to improve the knowledge of the top coal cavability evaluation. A range of parameters that affect the top coal cavability were first identified. Afterward, a number of cavability assessment methods and classifications were reviewed. The result is important in that it assists researchers in developing an advanced and reliable tool for the top coal cavability evaluation.

关键词： Longwall top coal caving Cavability Numerical modelling Caving mechanism Caving classification

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A novel elastoplastic model for Yunnan sandstone under poly-axial loading

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International Journal of Mining Science and Technology 2023年第7期33卷 801-814页

作者： Xu Li Guangyao Si joung oh Ismet Canbulat Rui Kong Jian Zhang School of Minerals and Energy Resources Engineering University of New South WalesSydney NSW 2052Australia Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines Northeastern UniversityShenyang 110819China School of Safety Science and Engineering Henan Polytechnic UniversityJiaozuo 454003China

The lack of understanding of plastic hardening(softening)laws,especially under anisotropic stress conditions,results in inappropriate geotechnical *** of the yielding envelopes do not consider the effect of intermediate principal stress and the influence of Lode's *** addition,the application of plastic flow rules regarding yielding surfaces compromises the softening of rock internal friction as well as the influence of Lode's angle on the plastic ***,the ductility to brittleness transition in the intermediate principal stress direction still requires a theoretical *** this study,based on poly-axial testing results of Yunnan sandstone,we adopted a failure criterion with the intermediate principal stress proposed by Menétrey and *** proposed new failure envelope was applied to capture the plastic evolution of rock samples.A plastic hardening-softening model is constructed,based on the framework of the plastic *** softening envelope is modified to better present the stress drop and considers the deterioration of rock internal friction in the post-peak stage of poly-axial *** differential of plastic potential according to the principal stresses is also modified,considering the rotation of Lode's angle in the poly-axial loading *** model results were compared with laboratory testing results,which showed great consistency across 9 different loading tests(5 under triaxial stress and 4 under poly-axial stress with 22 stress-strain curves in total).The induced brittleness by the intermediate principal stress is also well captured by the proposed model.

关键词： Elastoplastic model Rock mechanics Poly-axial stress state True-triaxial

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An investigation of machine learning techniques to estimate minimum horizontal stress magnitude from borehole breakout

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International Journal of Mining Science and Technology 2022年第5期32卷 1021-1029页

作者： Huasheng Lin Sarvesh Kumar Singh Zizhuo Xiang Won Hee Kang Simit Raval joung oh Ismet Canbulat Glencore Coal Assets Australia Mount Thorley 2330Australia School of Minerals and Energy Resources Engineering University of New South WalesSydney 2052Australia Centre for Infrastructure Engineering School of EngineeringWestern Sydney UniversityPenrith 2751Australia

Borehole breakout is a widely utilised phenomenon in horizontal stress orientation determination,and breakout geometrical parameters,such as width and depth,have been used to estimate both horizontal stress ***,the accuracy of minimum horizontal stress estimation from borehole breakout remains relatively low in comparison to maximum horizontal stress *** paper aims to compare and improve the minimum horizontal stress estimation via a number of machine learning(ML)regression techniques,including parametric and non-parametric models,which have rarely been *** models were trained based on 79 laboratory data from published literature and validated against 23 field data.A systematic bias was observed in the prediction for the validation dataset whenever the horizontal stress value exceeded the maximum value in the training ***,the pattern was captured,and the removal of systematic bias showed that the artificial neural network is capable of predicting the minimum horizontal stress with an average error rate of 10.16%and a root mean square error of 3.87 MPa when compared to actual values obtained through conventional in-situ measurement *** is a meaningful improvement considering the importance of in-situ stress knowledge for underground operations and the availability of borehole breakout data.

关键词： Borehole breakout In-situ stress estimation Comparative analysis Machine learning

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Quantitative assessment of the spatio-temporal correlations of seismic events induced by longwall coal mining

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第5期14卷 1406-1420页

作者： Shuyu Wang Guangyao Si Changbin Wang Wu Cai Binglei Li joung oh Ismet Canbulat School of Minerals and Energy Resources Engineering University of New South WalesSydney2052Australia State Key Laboratory of Coal Resources and Safe Mining School of MinesChina University of Mining and TechnologyXuzhou221116China Zijin School of Geology and Mining Fuzhou UniversityFuzhou350108China

Rock failure process as a natural response to mining activities is associated with seismic events, which can pose a potential hazard to mine operators, equipment and infrastructures. Mining-induced seismicity has been found to be internally correlated in both time and space domains as a result of rock fracturing during progressive mining activities. Understanding the spatio-temporal(ST) correlation of mininginduced seismic events is an essential step to use seismic data for further analysis, such as rockburst prediction and caving assessment. However, there are no established methods to perform this critical task. Input parameters used for the prediction of seismic hazards, such as the time window of past data and effective prediction distance, are determined based on site-specific experience without statistical or physical reasons to support. Therefore, the accuracy of current seismic prediction methods is largely constrained, which can only be addressed by quantitively assessing the ST correlations of mininginduced seismicity. In this research, the ST correlation of seismic event energy collected from a study mine is quantitatively analysed using various statistical methods, including autocorrelation function(ACF), semivariogram and Moran’s I analysis. In addition, based on the integrated ST correlation assessment, seismic events are further classified into seven clusters, so as to assess the correlations within individual clusters. The correlation of seismic events is found to be quantitatively assessable, and their correlations may vary throughout the mineral extraction process.

关键词： Spatial correlation Temporal correlation Autocorrelation function(ACF) Semivariogram Scale of fluctuation

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A hybrid swarm population of Pinus densiflora × P. sylvestris inferred from sequence analysis of chloroplast DNA and morphological characters

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Journal of Forestry Research 2013年第1期24卷 53-60页

作者： Young Hee joung Jerry L. Hill Jung oh Hyun Ding Mu Juchun Luo Do Hyung Lee Takayuki Kawahara Jeung Keun Suh Mark S. Roh Chonnam National University School of Biological Sciences & TechnologyGwangjuKorea US Department of Agriculture Forest ServiceDorena Genetic Resource CenterWashington State UniversityPullmanWA99164USA Seoul National University College of Agriculture and Life SciencesSeoulKorea Chinese Academy of Agricultural Science Beijing Forestry University College of Resources and Environment Yeungnam University College of Natural ResourcesDepartment of Forest ResourcesGyeongsanKorea Hokkaido Research Center Forestry and Forest Products Research InstituteSapporoJapan. Dankook University School of Bio-Resource ScienceDepartment of Environment HorticultureCheonanKorea. US Department of Agriculture Agricultural Research ServiceUS National ArboretumFloral and Nursery Plants Research UnitBeltsvilleMD 20705USA.

To confirm a hybrid swarm population of Pinus densiflora × P. sylvestris in Jilin, China, we used needles and seeds from P. densiflora, P. sylvestris, and P. densiflora × P. sylvestris collected from natural stands or experimental stations to study whether shoot apex morphology of 4-year old seedlings can be correlated with the sequence of a chloroplast DNA simple sequence repeat marker （cpDNA SSRs）. Total genomic DNA was extracted and subjected to sequence analysis of the pine cpDNA SSR marker Pt15169. Results show that morphological characters from 4-year old seedlings did not correlate with sequence variants of this marker. Marker haplotypes from all P. sylvestris trees had a CTAT element that was absent from all sampled P. densiflora trees. However, both haplotype classes involving this insertion/deletion element were found in a P. densiflora × P. sylvestris population and its seedling progeny. It was concluded that the P. densiflora × P. sylvestris accessions sampled from Jilin, China resulted from bi-directional crosses, as evidenced by both species’ cpDNA haplotypes within the hybrid swarm population.

关键词： P. sylvestris var. sylvestriformis chloroplast DNA simplesequence repeat sequencing hybrid swarm population

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Risk factors affecting pancreatic fistulas after pancreaticoduodenectomy

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World Journal of Gastroenterology 2008年第45期14卷 6970-6974页

作者： Yun-Mee Choe Keon-Young Lee Cheong-Ah oh joung-Bum Lee Sun Keun Choi Yoon-Seok Hur Sei-Joong Kim Young Up Cho Seung-Ik Ahn Kee-Chun Hong Seok-Hwan Shin Kyung-Rae Kim Department of Surgery Inha University Hospital

AIM: To analyze the risk factors of pancreatic leakage after ***: We retrospectively reviewed 172 consecutive patients who had undergone pancreatico-duodenectomy at Inha University Hospital between April 1996 and March 2006. We analyzed the pancreatic fistula rate according to the clinical characteristics, the pathologic and laboratory findings, and the anastomotic ***: The incidence of developing pancreatic fistulas in patients older than 60 years of age was 21.7% (25/115), while the incidence was 8.8% (5/57) for younger patients; the difference was significant (P = 0.03). Patients with a dilated pancreatic duct had a lower rate of post-operative pancreatic fistulas than patients with a non-dilated duct (P = 0.001). Other factors, including clinical features, anastomotic methods, and pathologic diagnosis, did not show any statistical difference. CONCLUSION: Our study demonstrated that pancreatic fistulas are related to age and a dilated pancreatic duct. The surgeon must take these risk factors into consideration when performing a pancre-aticoduodenectomy.

关键词： Pancreaticoduodenectomy Pancreatic fistula Pancreatic leakage

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