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science of empirical design in mining ground control

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International Journal of Mining science and Technology 2016年第3期26卷 461-470页

作者： mark Christopher MsHA Pittsburgh Safety & Health Technology Center

Many problems in rock engineering are limited by our imperfect knowledge of the material properties and failure mechanics of rock masses. Mining problems are somewhat unique, however, in that plenty of real world experience is generally available and can be turned into valuable experimental *** pillar that is developed, or stope that is mined, represents a full-scale test of a rock mechanics design. By harvesting these data, and then using the appropriate statistical techniques to interpret them,mining engineers have developed powerful design techniques that are widely used around the *** empirical methods are readily accepted because they are simple, transparent, practical, and firmly tethered to reality. The author has been intimately associated with empirical design for his entire career, but his previous publications have described the application of individual techniques to specific problems. The focus of this paper is the process used to develop a successful empirical method. A sixstage process is described: identification of the problem, and of the end users of the final product; development of a conceptual rock mechanics model, and identification of the key parameters in that model;identification of measures for each of the key parameters, and the development of new measures(such as rating scales) where necessary; data sources and data collection; statistical analysis; and packaging of the final product. Each of these stages has its own potential rewards and pitfalls, which will be illustrated by incidents from the author's own experience. The ultimate goal of this paper is to provide a new and deeper appreciation for empirical techniques, as well as some guidelines and opportunities for future developers.

关键词： Design Pillar stope Empirical statistics Modeling

Towards a versatile point-of-care systemcombining femtosecond laser generatedmicrofluidic channels and direct laserwritten microneedle arrays

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Microsystems & Nanoengineering 2019年第1期5卷 606-614页

作者： Anika Trautmann Gian-Luca roth Benedikt Nujiqi Thomas Walther Ralf Hellmann Applied Laser and Photonics Group University of Applied Sciences AschaffenburgWuerzburger Strasse 4563743 AschaffenburgGermany Institute of Applied Physics Technische Universität DarmstadtSchlossgartenstrasse 764289 DarmstadtGermany

Microneedle-based microfluidic systems have a great potential to become well-accepted medical devices for simple,accurate,and painless drug delivery and lab-on-a-chip *** this work,we report on a novel hybrid approach combining femtosecond direct laser written microneedles with femtosecond laser generated microfluidic channels providing an important step towards versatile medical point-of-care *** microneedle arrays are fabricated by a laser system designed for two-photon polymerization *** tests of two different types of truncated cone-shaped microneedle arrays prepared from OrmoComp^(■)give information about the microneedle mechanical strength,and the results are compared to skin insertion ***-dimensional microchannels are directly created inside PMMA bulk material by an ultrashort pulse laser system with vertical channels having adjustable cross-sectional areas,which allow attaching of microneedles to the microfluidic system.A comprehensive parameter study varying pulse duration and repetition rate is performed on two-photon polymerization to identify an optimal laser power range for fabricating microneedles using the same pulse duration and repetition rate as for *** addresses the advantage of a single laser system process that overcomes complex fabrication methods.A proof of concept flow test with a rhodamine B dye solution in distilled water demonstrates that the combination of microneedles and microchannels qualifies for microfluidic injection and extraction applications.

关键词： arrays versatile needle

sOME PROPERTIEs OF COMMUTING AND ANTI-COMMUTING m-INVOLUTIONs

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Acta Mathematica scientia 2012年第2期32卷 631-644页

作者： mark Yasuda 9525 Compass Point Drive south San DiegoCA 92126U.S.A.

We define an m-involution to be a matrix K ∈ Cn×n for which Km -= I. In this article, we investigate the class sm （A） of m-involutions that commute with a diagonalizable matrix A E Cn×n. A number of basic properties of sm （A） and its related subclass sm （A, X） are given, where X is an eigenvector matrix of A. Among them, sm （A） is shown to have a torsion group structure under matrix multiplication if A has distinct eigenvalues and has non-denumerable cardinality otherwise. The constructive definition of sm （A, X） allows one to generate all m-involutions commuting with a matrix with distinct eigenvalues. some related results are also given for the class s,, （A） of m-involutions that anti-commute with a matrix A ∈ Cnn×n.

关键词： Centrosymmetric skew-centrosymmetric bisymmetric involution eigenval-ues

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

Assessing support alternatives for longwall gateroads subject to changing stress

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International Journal of Mining science and Technology 2021年第1期31卷 103-110页

作者： Gabriel s.Esterhuizen I.Berk Tulu Dave F.Gearhart Heather Dougherty mark Van Dyke National Institute for Occupational safety and Health Pittsburgh Mining Research DivisionPittsburghPA 15236USA West Virginia University MorgantownWV 26506USA

Longwall gateroad entries are subject to changing horizontal and vertical stress induced by redistribution of loads around the extracted *** stress changes can result in significant deformation of the entries that may include roof sag,rib dilation,and floor *** operators install different types of supports to control the ground response and maintain safe access and ventilation of the longwall *** paper describes recent research aimed at quantifying the effect of longwall-induced stress changes on ground stability and using the information to assess support *** research included monitoring of ground and support interaction at several operating longwall mines in the U.s.,analysis and calibration of numerical models that adequately represent the bedded rock mass,and observation of the support systems and their response to changes in *** models were then used to investigate the impact of geology and stress conditions on ground deformation and support response for various depths of cover and geologic *** research results were summarized in two regression equations that can be used to estimate the likely roof deformation and height of roof yield due to longwall-induced stress *** information is then used to assess the ability of support systems to maintain the stability of the *** application of the method is demonstrated with a retrospective analysis of the support performance at an operating longwall mine that experienced a headgate roof *** method is shown to produce realistic estimates of gateroad entry stability and support performance,allowing alternative support systems to be assessed during the design and planning stage of longwall operations.

关键词： Longwall Gateroad support design Coal standing support

Unanticipated multiple seam stresses from pillar systems behaving as pseudo gob–case histories

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International Journal of Mining science and Technology 2017年第1期27卷 131-137页

作者： Gauna Michael mark Christopher Pittsburgh safety and Health Technology Center Mine Safety and Health Administration(MSHA)PittsburghPA 15236USA

Underground coal mining in the U.s. is conducted in numerous regions where previous workings exist above and/or below an actively mined seam. Miners know that overlying or underlying fully extracted coal areas, also known as gob regions, can result in abutment stresses that affect the active mining. If there was no full extraction, and the past mining consists entirely of intact pillars, the stresses on the active seam are usually minimal. However, experience has shown that in some situations there has been sufficient yielding in overlying or underlying pillar systems to cause stress transfer to the adjoining larger pillars or barriers, which in turn, transfer significant stresses onto the workings of the active seam. In other words, the overlying or underlying pillar system behaves as a ‘‘pseudo gob." The presence of a pseudo gob is often unexpected, and the consequences can be severe. This paper presents several case histories, summarized briefly below, that illustrate pseudo gob phenomenon:(1) pillar rib degradation at a West Virginia mine at 335 m depth that contributed to a rib roll fatality,(2) pillar rib deterioration at a Western Kentucky mine at 175 m depth that required pillar size adjustment and installation of supplemental bolting,(3) roof deterioration at an eastern Kentucky mine at 400 m depth that stopped mine advance and required redirecting the section development,(4) coal burst on development at an eastern Kentucky mine at 520 m depth that had no nearby pillar recovery, and(5) coal burst on development at a West Virginia mine at the relatively shallow depth of 335 m that also had no nearby pillar recovery. The paper provides guidance so that when an operation encounters a potential pseudo gob stress interaction the hazard can be mitigated based on an understanding of the mechanism encountered.

关键词： Underground mining Coal Multiple seam Gob Ground control

Preventing roof fall fatalities during pillar recovery:A ground control success story

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International Journal of Mining science and Technology 2017年第1期27卷 107-113页

作者： mark Christopher Gauna Michael MsHA Pittsburgh Safety and Health Technology CenterPittsburghPA 15236USA

For decades, pillar recovery accounted for a quarter of all roof fall fatalities in underground coal *** showed that a miner on a pillar recovery section was at least three times more likely to be killed by a roof fall than other coal miners. since 2007, however, there has been just one fatal roof fall on a pillar line. This paper describes the process that resulted in this historic achievement. It covers both the key research findings and the ways in which those insights, beginning in the early 2000 s, were implemented in mining practice. One key finding was that safe pillar recovery requires both global and local *** stability is addressed primarily through proper pillar design, and became a major focus after the2007 Crandall Canyon mine disaster. But the most significant improvements resulted from detailed studies that showed that local stability, defined as roof control in the immediate work area, could be achieved with three interventions:(1) leaving an engineered final stump, rather than extracting the entire pillar,(2) enhancing roof bolt support, particularly in intersections, and(3) increasing the use of mobile roof supports(MRs). A final component was an emphasis on better management of pillar recovery *** included a focus on worker positioning, as well as on the pillar and lift sequences, MRs operations,and hazard identification. As retreat mines have incorporated these elements into their roof control plans,it has become clear that pillar recovery is not ‘‘inherently unsafe." The paper concludes with a discussion of the challenges that remain, including the problems of rib falls and coal bursts.

关键词： Retreat mining Roof support Room-and-pillar Ground control

MAPPING THE DAMAGED ZONE AROUND THE CRACK TIP IN HIGH DENsITY POLYETHYLENE WITH sYNCHROTRON MICROFOCUs sMALL ANGLE X-RAY sCATTERING TECHNIQUE

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Chinese Journal of Polymer science 2010年第2期28卷 165-170页

作者： Hans-Friedrich Enderle Dieter Lilge stephan V.roth Rainer Gehrke Jens Rieger 门永锋 Basell Polyolefine GmbH R&D65926 FrankfurtGermany HAsYLAB am DEsY Notkestr.8522607 HamburgGermany BAsF sE Polymer Research67056 LudwigshafenGermany state Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of Sciences

The structural changes around a crack tip in a high density polyethylene were investigated by means of scanning synchrotron microfocus small-angle X-ray scattering technique. The scattering data confirm the process of craze structure development near a crack tip based on the evolution of voids. In addition, it was found that the main stress in the plastic zone near a crack tip exhibited a gradient distribution with respect to its strength and direction. The whole damaged area showed a strain distribution indicating a flow behavior toward the crack tip.

关键词： High density polyethylene Microfocus sAXs Crack tip Voids.

Preventing aggressive prostate cancer with proven ：ardiovascular disease preventive methods

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Asian Journal of Andrology 2015年第6期17卷 874-877页

作者： mark A Moyad Department of Urology University of MichiganMedical Center 1500 East Medical Center DriveAnn Arbor MI 48109 USA

Cardiovascular disease （CVD） has been the number one cause of death in the U.s. for 114 of the last 115 years. Risk factors for prostate cancer have primarily mirrored risk proven risk factors for CVD, especially aggressive disease. Obesity, dyslipidemia, glucose intolerance, metabolic syndrome, unhealthy dietary habits or caloric excess, lack of physical activity, and inflammation are just some of these shared risk factors. The evidence also suggests proven CVD preventive measures are identical to prostate cancer preventive measures, especially in regard to aggressive disease. Thus, apart from lifestyle measures that can encourage optimal heart and prostate health there are potentially several dietary supplements that need to be avoided in healthy men because they may also increase the risk of prostate cancer. However, there are also several low-cost, generic, safe in the appropriate individuals, and naturally derived agents that could reduce prostate cancer risk, and these can be discussed and remembered utilizing the acronym s.A.M. （statins, aspirin, and/or metformin）.

关键词： Preventing aggressive methods