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Analytical investigations of in situ stress inversion from borehole breakout geometries

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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

Bubble size as a function of some situational variables in mechanical flotation machines

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Journal of Central south University 2014年第2期21卷 720-727页

作者：张炜 Jan E.Nesset James A.Finch Mining and mineral resources Division Department of Business AdministrationChinalco China Copper Corporation Limited department of Mining and Materials Engineering McGill University

The specific results of the work investigating the effect of gas density and water temperature on bubble size were *** were surrogate variables designed to investigate the effect of viscosity(varying water temperature) and altitude(varying gas density).The results show that there is a measurable but relatively small effect of gas density on bubble *** D32 is revealed to increase proportionally as(ρ0/ρg)*** projected impact on flotation kinetics at 4500 m versus sea level is small,of the order of 0.5% recovery loss for a bank of eight flotation *** effect of water temperature(4-40 °C) on bubble size is more significant than gas *** relationship correlates with water viscosity values quite closely.A finding that D32 increases proportionally as(μ/μ20)0.776 highlights the importance of accounting for viscosity effects if,for example,large process temperature fluctuations or deviation from design/test conditions are expected.

关键词： flotation frother bubble size viscosity altitude

Effect of solids on pulp and froth properties in flotation

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Journal of Central south University 2014年第4期21卷 1461-1469页

作者：张炜 James A.Finch Mining & mineral resources Division department of Business Administration Chinalco China Copper Corporation Limited department of Mining and Materials Engineering McGill University

Froth flotation is a widely used process of particle separation exploiting differences in surface properties. It is important to point out that overall flotation performance(grade and recovery) is a consequence of the quality and quantity of the solid particles collected from the pulp phase, transported into the froth phase, and surviving as bubble-particle aggregates into the overflow. This work will focus on studying these phenomena and will incorporate the effects of particle hydrophobicities in the 3-phase system. Solids are classed as either hydrophilic non-sulphide gangue(e.g. silica, talc), hydrophilic sulphide(e.g. pyrite), or hydrophobic sulphide(e.g. sphalerite). Talc is a surface-active species of gangue that has been shown to behave differently from silica(frother adsorbs on the surface of talc particles). Both are common components of ores and will be studied in detail. The focus of this work is to investigate the role of solids on pulp hydrodynamics, froth bubble coalescence intensity, water overflow rate with solids present, and in particular, the interactions between solids, frother and gas on the gas dispersion parameters. The results show that in the pulp zone there is no effect of solids on bubble size and gas holdup; in the froth zone, although hydrophilic particles solely do not effect on the water overflow rate, hydrophobic particles produce higher intensity of rates on water overflow and bubble coalescence, and many be attributed to the water reattachment.

关键词： flotation frothers bubble size coalescence gas holdup hydrophobicity

Effect of some operational variables on bubble size in a pilot-scale mechanical flotation machine

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Journal of Central south University 2014年第3期21卷 1077-1084页

作者：张炜 J.E.Nesset J.A.Finch Mining and mineral resources Division Department of Business AdministrationChinalco China Copper Corporation Limited department of Mining and Materials Engineering McGill University

This work aims to provide a relationship of how the key operational variables of frother type and impeller speed affect the size of bubble （D32）. The study was performed using pilot-scale equipment （0.8 m^3） that is up to two orders of magnitude larger than equipment used for studies performed to date by others, and incorporated the key process variables of frother type and impeller speed. The results show that each frother family exhibits a unique CCC95-HLB relationship dependent on n （number of C-atoms in alkyl group） and m （number of propylene oxide group）. Empirical models were developed to predict CCC95 from HLB associated with other two parameters a and ft. The impeller speed-bubble size tests show that D32 is unaffected by increased impeller tip speed across the range of 4.6 to 9.2 m/s （representing the industrial operating range）, although D32 starts to increase below 4.6 m/s. The finding is valid for both coalescing and non-coalescing conditions. The results suggest that the bubble size and bubble size distribution （BSD） being created do not change with increasing impeller speed in the quiescent zone of the flotation.

关键词： flotation bubble size operational variables critical coalescence concentration hydrophile-lipophile balance impellerspeed

What constitutes failure of medical therapy in the changing landscape of Crohn's disease?

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Laparoscopic, Endoscopic and Robotic Surgery 2022年第4期5卷 158-160页

作者： Nguyen Huynh Henry Wang Kar Yin Fok James Wei Tatt Toh Division of Colorectal Surgery Department of SurgeryWestmead HospitalSydneyNew South WalesAustralia Westmead Clinical School The University of SydneySydneyNew South WalesAustralia

The management of Crohn's disease has evolved rapidly in the era of immunomodulators and *** this,a significant proportion of patients with Crohn's disease ultimately require surgical *** of the indications for operative management includes failure of medical *** report two cases of patients with complicated Crohn's disease who have exhausted medical therapy and failed medical *** both cases,the patients developed large complex intra-abdominal phlegmons and intractable symptoms of intermittent pain,partial obstruction and/or infectious complications requiring operative ***'s disease can present with a wide spectrum of *** the complexity of management in Crohn's disease,it is important for both physicians and surgeons to be aware of what constitutes failure of medical therapy and when it may be important to consider surgical involvement.

关键词： Crohn's disease Phlegmon Laparoscopic surgery Failure of medical therapy Ileocecal resection

Challenges against CO_(2) abatement strategies in cement industry: A review

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Journal of Environmental Sciences 2021年第6期33卷 84-101页

作者： Emad Benhelal Ezzatollah Shamsaei Muhammad Imran Rashid department of Chemical Engineering The University of NewcastleNew South Wales 2287Australia department of Civil Engineering Monash UniversityClayton 3800VictoriaAustralia Chemical Polymer and Composite Materials Engineering DepartmentUniversity of Engineering and TechnologyLahore(New Campus)39021Pakistan

Cement industry is an intensive source of fuel consumption and greenhouse gases(GHGs) emissions. This industry is responsible for 5% of GHGs emissions and is among the top industrial sources of carbon dioxide(CO_(2)) emissions. Therefore, CO_(2) emissions reduction from cement production process has been always an appealing subject for researches in universities and industry. Various efforts have been carried out to mitigate the huge mass of CO_(2) emissions from the cement industry. Although, majority of these strategies are technically viable, due to various barriers, the level of CO_(2) mitigation in cement industry is still not satisfactory. Among numerous researches on this topic, only a few have tried to answer why CO_(2) abatement strategies are not globally practiced yet. This work aims to highlight the challenges and barriers against widespread and effective implementation of CO_(2) mitigation strategies in the cement industry and to propose practical solutions to overcome such barriers.

关键词： CO_(2)emissions CO_(2)mitigation Cement industry Challenges of CO_(2)reduction

A novel approach to prevent bubble coalescence during measurement of bubble size in flotation

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Journal of Central south University 2014年第1期21卷 338-343页

Effect of frothers in preventing bubble coalescence during flotation of minerals has long been *** evaluate the performance of a frother,an apparatus to measure the bubble size is a basic *** Bubble Size Analyzer(MBSA) or bubble viewer that has been developed and completed by McGill University's mineral Processing Group during the last decade is a unique instrument to serve this *** parameters which are thought to influence the bubble size measurements by McGill bubble viewer include water quality and frother concentration in the *** show that there is no difference in Sauter mean(D32) when tap or de-ionized water was used instead of process ***,the frother concentration,in this research DowFroth 250(DF250),inside the chamber exhibited a pronounced effect on bubble *** concentration below a certain point can not prevent coalescence inside the chamber and therefore caution must be taken in plant *** was also noted that the frother concentration which has been so far practiced in plant measurements(CCC75-CCC95) is high enough to prevent coalescence with the bubble viewer.

关键词： flotation frother bubble size bubble coalescence

Application of Geochemistry and VNIR Spectroscopy in Mapping Heavy Metal Pollution of Stream Sediments in the Takab Mining Area, NW of Iran

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Acta Geologica Sinica(English Edition) 2018年第6期92卷 2382-2394页

作者： Parisa PIROOZFAR Samad ALIPOUR Soroush MODABBERI David COHEN department of Geology Faculty of SciencesUrmia University School of Geology University of Tehran School of Biological Earth and Environmental SciencesNew South Wales University

This study considered the possibility of using visible and near infrared(VNIR) spectral absorption feature parameters(SAFPs) in predicting the concentration and mapping the distribution of heavy metals in sediments of the Takab area. In total, 60 sediment samples were collected along main streams draining from the mining districts and tailing sites, in order to measure the concentration of As, Co, V, Cu, Cr, Ni, Hg, Ti, Pb and Zn and the reflectance spectra(350–2500 nm). The quantitative relationship between SAFPs(Depth500 nm, R610/500 nm, R1344/778 nm, Area500 nm, Depth2200 nm, Area2200 nm, Asym2200 nm) and geochemical data were assessed using stepwise multiple linear regression(SMLR) and enter multiple linear regression(EMLR) methods. The results showed a strong negative correlation between Ni and Cr with Area2200 nm, a significant positive correlation between As and Asym2200 nm, Ni and Co with Depth2200 nm, as well as Co, V and total values with Depth500 nm. The EMLR method eventuated in a significant prediction result for Ni, Cr, Co and As concentrations based on spectral parameters, whereas the prediction for Zn, V and total value was relatively weak. The spatial distribution pattern of geochemical data showed that mining activities, along with the natural weathering of base metal occurrences and rock units, has caused high concentrations of heavy metals in sediments of the Sarough River tributaries.

关键词： heavy metals SAFPs VNIR spectroscopy multiple linear regression Takab Iran

Borehole deformation based in situ stress estimation using televiewer data

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第9期15卷 2475-2481页

作者： Hamid Roshan Danqi Li Ismet Canbulat Klaus Regenauer-Lieb School of minerals and Energy resources Engineering University of New South WalesSydneyNSW2052Australia WA School of Mines MineralsEnergy and Chemical EngineeringCurtin UniversityPerthWA6102Australia

The knowledge of in situ stress is critical in safe and optimised extraction of minerals and energy *** situ stresses are either measured directly(***)or estimated indirectly(*** breakouts).Borehole breakout analysis for in situ stress estimation is considered a relatively simple and cost-efficient *** technique,however,poses certain limitations such as complexities with progressive formation of breakouts and it requires inputs such as rock failure parameters that are not often *** a result,significant effort has been made to develop new indirect methods for in situ stress *** deformation analysis using four-arm caliper has been recently proposed for in situ stress estimation and has shown promising *** this study,we demonstrate a new methodology that analyses the borehole televiewer data with the technique of borehole deformation analysis to estimate the in situ stresses through a field case *** advantages and challenges of using borehole televiewer data for stress estimation based on borehole deformation analysis are discussed and the best practice to obtain the reliable results is *** limitations of using fourarm caliper and borehole deformation analysis for in situ stress estimation are also discussed and it is shown how televiewer data can overcome such ***,the in situ stress results obtained from televiewer data and borehole deformation analysis are compared with independent in situ stress measurements to show the robustness and reliability of the proposed methodology.

关键词： In situ stress Borehole deformation Televiewer Elastic properties Downhole logging