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Assessment of strain bursting in deep tunnelling by using the finite-discrete element method

Journal of Rock Mechanics and Geotechnical Engineering 2019年第1期11卷 12-37页

作者： Ioannis Vazaios mark s.diederichs nicholas vlachopoulos Department of Ceological saences and Ceological Engineering Queen's UniversityKingstonCanada

Rockbursting in deep tunnelling is a complex phenomenon posing significant challenges both at the design and construction stages of an underground excavation within hard rock masses and under high in situ stresses. While local experience, field monitoring, and informed data-rich analysis are some of the tools commonly used to manage the hazards and the associated risks, advanced numerical techniques based on discontinuum modelling have also shown potential in assisting in the assessment of rockbursting. In this study, the hybrid finite-discrete element method(FDEM) is employed to investigate the failure and fracturing processes, and the mechanisms of energy storage and rapid release resulting in bursting, as well as to assess its utility as part of the design process of underground *** the calibration of the numerical model to simulate a deep excavation in a hard, massive rock mass, discrete fracture network(DFN) geometries are integrated into the model in order to examine the impact of rock structure on rockbursting under high in situ stresses. The obtained analysis results not only highlight the importance of explicitly simulating pre-existing joints within the model, as they affect the mobilised failure mechanisms and the intensity of strain bursting phenomena, but also show how the employed joint network geometry, the field stress conditions, and their interaction influence the extent and depth of the excavation induced damage. Furthermore, a rigorous analysis of the mass and velocity of the ejected rock blocks and comparison of the obtained data with well-established semi-empirical approaches demonstrate the potential of the method to provide realistic estimates of the kinetic energy released during bursting for determining the energy support demand.

关键词： Rockburst Finite-discrete element method(FDEM) Deep tunnelling Hard rock excavations Brittle fracturing Discrete fracture network(DFN)

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An in situ monitoring campaign of a hard rock pillar at great depth within a Canadian mine

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Journal of Rock Mechanics and Geotechnical Engineering 2020年第3期12卷 427-448页

作者： Bradley Forbes nicholas vlachopoulos.mark s.diederichs Andrew J.Hyett Allan Punkkinen Department of Geological sciences and Geological Engineering Queen’s UniversityKingstonOntarioK7L 3N6Canada Department of Civil Engineering Royal Military College of CanadaKingstonOntarioK7K 7B4Canada YieldPoint Inc. KingstonOntarioK7M 4W9Canada Normet Canada Ltd. LivelyOntarioP3Y 0B3Canada

A recent research campaign at a Canadian nickel-copper mine involved instrumenting a hard rock sill drift pillar with an array of multi-point rod extensometers,distributed optical fibre strain sensors,and borehole pressure cells(BHPCs).The instrumentation spanned across a 15.24 m lengthwise segment of the relatively massive granitic pillar situated at a depth of 2.44 km within the *** May 2016 and March 2017,the pillar’s displacement and pressure response were measured and correlated with mining activities on the same level as the pillar,including:(1)mine-by of the pillar,(2)footwall drift development,and(3)ore body stoping *** displacements of the pillar,the extensometers provided high temporal resolution(logged hourly)and the optical fibre strain sensors provide high spatial resolution(measured every 0.65 mm along the length of each sensor).The combination of sensing techniques allowed centimetre-scale rock mass bulking near the pillar sidewalls to be distinguished from microstrain-scale fracturing towards the core of the ***,the influence and extent of a mine-scale schistose shear zone transecting the pillar was *** converting measured rock mass displacement to velocity,a process was demonstrated which allowed mining activities inducing displacements to be categorised by time-duration and cumulative *** over half of the analysed mining activities,displacements were determined to prolong for over an hour,predominately resulting in submillimetre cumulative displacements,but in some cases multi-centimetre cumulative displacements were *** time-dependent behaviour was more pronounced within the vicinity of the plumb shear *** measurements were also used to assess selected support member load and elongation mobilisation per mining *** was found that a combined static load and elongation capacity of reinforcing members was essential to maintaining excavation stability,while

关键词： Hard rock pillar Rockburst Rock mass bulking Distributed optical fibre strain sensing Extensometer In situ monitoring High stress Dynamic support

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Calibration of coupled hydro-mechanical properties of grain-based model for simulating fracture process and associated pore pressure evolution in excavation damage zone around deep tunnels

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Journal of Rock Mechanics and Geotechnical Engineering 2021年第1期13卷 60-83页

作者： Kiarash Farahmand mark s.diederichs Department of Geological sciences and Geological Engineering Queen’s UniversityKingstonOntarioK7L 3N6Canada Golder Associates VancouverBritish ColumbiaCanada

The objective of this paper is to develop a methodology for calibration of a discrete element grain-based model(GBM)to replicate the hydro-mechanical properties of a brittle rock measured in the laboratory,and to apply the calibrated model to simulating the formation of excavation damage zone(EDZ)around underground ***,a new cohesive crack model is implemented into the universal distinct element code(UDEC)to control the fracturing behaviour of materials under various loading ***,a methodology for calibration of the components of the UDEC-Voronoi model is *** role of connectivity of induced microcracks on increasing the permeability of laboratory-scale samples is *** calibrated samples are used to investigate the influence of pore fluid pressure on weakening the drained strength of the laboratory-scale *** validity of the Terzaghi’s effective stress law for the drained peak strength of low-porosity rock is tested by performing a series of biaxial compression test ***,the evolution of damage and pore pressure around two unsupported circular tunnels in crystalline granitic rock is studied.

关键词： Coupled hydro-mechanical properties Excavation damage zone(EDZ) Grain-based model(GBM)calibration stress-fracturing of rock Cohesive crack model stress-dependent permeability

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Predicting excavation damage zone depths in brittle rocks

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Journal of Rock Mechanics and Geotechnical Engineering 2016年第1期8卷 60-74页

作者： Matthew A.Perras mark s.diederichs Queen’s University Miller Hall36 Union StreetKingstonOntarioK7L 3N6Canada swiss Federal Institute of Technology Sonneggstrasse 5ZurichCH-8092Switzerland

During the construction of an underground excavation, damage occurs in the surrounding rock mass due in large part to stress changes. While the predicted damage extent impacts profile selection and support design, the depth of damage is a critical aspect for the design of permeability sensitive excavations, such as a deep geological repository(DGR) for nuclear waste. Review of literature regarding the depth of excavation damage zones(EDZs) indicates three zones are common and typically related to stress induced damage. Based on past developments related to brittle damage prediction using continuum modelling, the depth of the EDZs has been examined numerically. One method to capture stress induced damage in conventional engineering software is the damage initiation and spalling limit(DIsL) approach. The variability of depths predicted using the DIsL approach has been evaluated and guidelines are suggested for determining the depth of the EDZs around circular excavations in brittle rock masses. Of the inputs evaluated, it was found that the tensile strength produces the greatest variation in the depth of the EDZs. The results were evaluated statistically to determine the best fit relation between the model inputs and the depth of the EDZs. The best correlation and least variation were found for the outer EDZ and the highly damaged zone(HDZ) showed the greatest variation. Predictive equations for different EDZs have been suggested and the maximum numerical EDZ depths, represented by the 68% prediction interval, agreed well with the empirical evidence. This suggests that the numerical limits can be used for preliminary depth prediction of the EDZs in brittle rock for circular excavations.

关键词： Excavation damage zones(EDZs) Deep geological repository(DGR) Empirical depth prediction Numerical depth prediction Damage depth sensitivity Damage initiation and spalling limit(DIsL)

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Olympic Games and 24-hour movement behaviors:A match worth making

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Journal of sport and Health science 2024年第6期13卷 728-731页

作者： mark s.Tremblay nicholas Kuzik markus J.Duncan Diego Augusto santos silva CHEO Research Institute OttawaON K1H 8L1Canada Department of Pediatrics University of OttawaOttawaON K1H 8L1Canada Federal University of santa Catarina FlorianopolisSanta Catarina 88040-900Brazil

*** The Olympic motto,"Faster,Higher,stronger-Together",represents the pursuit of athletic excellence,united as a global community."Excellence,respect and friendship"are the Olympic *** the motto and values are multifaceted and holistic in nature,and all-encompassing in their reach while recognizing no single entity rises above the ***,these foundational statements anchor the Olympic movement in its quest to build a better world through sport.

关键词： movement Together pursuit

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Towards precision 24-hour movement behavior recommendations—The next new paradigm?

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Journal of sport and Health science 2024年第6期13卷 743-748页

作者： mark s.Tremblay markus J.Duncan nicholas Kuzik Diego Augusto santos silva Valerie Carson CHEO Research Institute OttawaON K1H 8L1Canada Department of Pediatrics University of OttawaOttawaON K1H 8L1Canada Federal University of santa Catarina Santa Catarina 88040900Brazil Faculty of Kinesiology Sportand RecreationUniversity of AlbertaEdmontonAB T6G 2H9Canada

*** The importance of physical activity(PA)for health is unequivocal.^(1)Accordingly,population-based recommendations for exercise,and more recently public health guidelines for PA,have been developed and released by authoritative groups for many decades.^(2)such guidelines emerged with leadership from the exercise physiology discipline and were rooted in,and loyal to,the importance of moderate-to-vigorous intensity PA(MVPA)or exercise.

关键词： movement behavior exercise

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Heart healthy equals prostate healthy and statins, aspirin, and/or metformin （s.A.M.） are the ideal recommendations for prostate cancer prevention

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Asian Journal of Andrology 2015年第5期17卷 783-791,I0008页

作者： mark A Moyad nicholas J Vogelzang Department of Urology University of Michigan Medical Center Ann Arbor Michigan USA Developmental Therapeutics Committee and Genitourinary Committee for Us Oncology Research Comprehensive Cancer Centers of Nevada Las Vegas Nevada USA

Cardiovascular disease （CVD） has been the number one cause of death in the U.s. for 114 of the last 115 years. Lifestyle factors that promote CVD also appear to increase prostate cancer risk and those that reduce CVD risk also appear to reduce the risk of prostate cancer. The largest randomized trials utilizing dietary supplements or pharmacologic agents for prostate cancer prevention （selenium and Vitamin E Cancer Prevention Trial [sELECT]） have also shed light on the problems and future solutions in this area. Dietary supplements that have not been found to be CVD protective, such as selenium and Vitamin E have not been found to be prostate protective. In addition, over exposure to specific anti-oxidants in nutritionally replete populations may be encouraging cancer growth. Futuretrials of dietary supplements to prevent prostate cancer could be problematic because by the time a definitive trial is initiated the participants will no longer be ＂deficient＂ in the nutrient being tested, which arguably occurred in the sELECT trial. It is also interesting that statins, aspirin, and/or metformin （s.A.M.） are 3 generic, low-cost, heart healthy agents derived from natural sources with separate mechanism of actions, which all appear to have the best benefit to risk ratio compared to any other agent available for prostate cancer prevention, especially aggressive disease, or as an ancillary agent （s） to conventional cancer treatment. It is time to focus on the forest over the trees and recommend proven CVD protective measures for men concerned about their risk of prostate cancer.

关键词： aspirin diet lifestyle metformin prostate cancer statins

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The origin of uniaxial negative thermal expansion in layered perovskites

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npj Computational Materials 2017年第1期3卷 89-96页

作者： Chris Ablitt sarah Craddock mark s.senn Arash A.Mostofi nicholas C.Bristowe Department of Materials Imperial College LondonLondon SW72AZUK Department of Chemistry University of OxfordSouth Parks RoadOxford OX13QRUK Department of Chemistry University of WarwickGibbet HillCoventry CV47ALUK Department of Physics Imperial College LondonLondon SW72AZUK school of Physical sciences University of KentCanterbury CT27NHUK

Why is it that ABO3 perovskites generally do not exhibit negative thermal expansion(NTE)over a wide temperature range,whereas layered perovskites of the same chemical family often do?It is generally accepted that there are two key ingredients that determine the extent of NTE:the presence of soft phonon modes that drive contraction(have negative Grüneisen parameters);and anisotropic elastic compliance that predisposes the material to the deformations required for NTE along a specific *** difference in thermal expansion properties is surprising since both ABO3 and layered perovskites often possess these ingredients in equal measure in their high-symmetry *** first principles calculations and symmetry analysis,we show that in layered perovskites there is a significant enhancement of elastic anisotropy due to symmetry breaking that results from the combined effect of layering and condensed rotations of oxygen *** feature,unique to layered perovskites of certain symmetry,is what allows uniaxial NTE to persist over a large temperature *** fundamental insight means that symmetry and the elastic tensor can be used as descriptors in high-throughput screening and to direct materials design.

关键词： perovskite layered symmetry

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Conversion of ethanol to 1,3-butadiene over Ag-ZrO_(2)/siO_(2) catalysts:The role of surface interfaces

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Journal of Energy Chemistry 2021年第3期30卷 7-15页

作者： Houqian Li Jifeng Pang nicholas R.Jaegers Libor Kovarik mark Engelhard Anthony W.savoy Jianzhi Hu Junming sun Yong Wang The Gene and Linda Voiland school of Chemical Engineering and Bioengineering Washington State UniversityPullmanWA 99164USA Dalian Institute of Chemical Physics Chinese Academy of SciencesDalian 116023LiaoningChina Institute for Integrated Catalysis Pacific Northwest National LaboratoryRichlandWA 99354USA

A series of Ag-ZrO_(2)/siO_(2) catalysts with different metal-support interfaces were synthesized in an effort to elucidate the roles of specific interfaces in controlling the ethanol to 1,3-butadiene conversion and *** to the results of detailed characterizations(***/pyridine-DRIFTs,XPs,TEM,NH3-TPD,and ^(1)H MAs NMR),it was found that the Ag-O-si interfaces significantly enhanced the dehydrogenation of ethanol while the presence of ZrO_(2) improved the interaction between Ag and ZrO_(2)/siO_(2),creating more Ag^(δ+)active *** high dispersion of ZrO_(2) on siO_(2) generated abundant Zr-O-si interfaces with medium and weak Lewis acidity,promoting the condensation of acetaldehyde to *** Zr-O-si interfaces in close interaction with Ag^(δ+)species played a critical role in the enhanced H transfer during the MPV reduction of crotonaldehyde to crotyl *** synergies among the interfaces resulted in retarded ethanol dehydration reactivity,balanced ethanol dehydrogenation and condensation reactions,and a subsequent high 1,3-butadiene yield.

关键词： Ethanol Catalysis 1,3-butadiene Interface Lewis acid site

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simplifying the shangRing technique for circumcision in boys and men: use of the no-flip technique with randomization to removal at 7 days versus spontaneous detachment

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Asian Journal of Andrology 2019年第4期21卷 324-331页

作者： mark A Barone Philip s Li Richard K Lee Daniel Ouma Millicent Oundo Mukhaye Barasa Jairus Oketch Patrick Otiende Nixon Nyangweso Mary Maina nicholas Kiswi Betty Chirchir Marc Goldstein Quentin D Awori EngenderHealth Washington DC 20004 USA Center for Male Reproductive Medicine and surgery Department of Urology Weill Cornell Medical College New York Presbyterian Hospital New York NY 10065 USA Engender Health Nairobi 00100 Kenya Bon sante Consulting Nairobi 00100 Kenya Homa Bay County Teaching and Referral Hospital Homa Bay 40300 Kenya Vipingo Health Centre Vipingo 80119 Kenya

To assess safety of the no-flip shangRing male circumcision technique and to determine clinical course and safety of spontaneous detachme nt (i.e., allowing the device to fall off), we con ducted a case series of no-flip shangRing circumcision combined with a randomized controlled trial of removal 7 days postcircumcision versus spontaneous detachment at two health facilities in Kenya. The primary outcome was the safety of the no-flip technique based on moderate and severe adverse events (AEs) during the procedure and through 42-day follow-up. A main sec on dary outcome was clinical course and safety of spontan eous detachment. Two hundred and thirty males 10 years and older underwent no?flip circumcision;114 randomized to 7-day removal and 116 to spontaneous detachment. All circumcisions were successfully completed. Overall 5.3%(6/114) of participants in the 7-day group and 1.7%(2/116) in the spontan eous group had an AE;with no d iff ere nces when compared to the 3% AE rate in historical data from African studies using the original flip technique (P = 0.07 and P = 0.79, respectively). Overall 72.4%(84/116) of participants in the spontaneous group wore the shangRing until it detached. Among the remaining (27.6%;32/116), the ring was removed, primarily at the participants1 request, due to pain or discomfort. There was no d iff ere nee in AE rates (P = 0.169), visit day declared healed (P= 0.324), or satisfaction (P= 0.371) between randomization groups. The median time to detachment was 14.0 (IQR: 7-21, range: 5-35) days. The no?flip technique and spontaneous detachment are safe, effective, and acceptable to boys and men 10 years and older. Phimosis and penile adhesions do not limit successful shangRing circumcision with the no-flip technique.

关键词： HIV prevention male circumcision device no-flip technique shangRing voluntary medical male circumcision

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