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A case study on the efficacy of different roof bolting schemes in Lhoist North America’s Crab Orchard mine

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International Journal of mining Science and Technology 2020年第1期30卷 99-104页

作者： Reece Kurre Gabriel walton Stantec Consulting Services Inc. Walnut CreekCA 94597USA Department of Geology and Geological Engineering Colorado School of MinesGoldenCO 80401USA

Roof bolting has long been used in underground mines across the world to provide ground *** roof bolts are cheap and easy to install with the use of specialized machines as a part of the production cycle. Lhoist North America’s Crab Orchard mine is an underground room and pillar limestone mine that uses mechanically anchored roof bolts for ground support. The mine currently employs two different roof bolting patterns: a standard 1.5 × 1.5 m pattern, and another 0.8 × 0.8 m pattern for use in areas with particularly hazardous roof conditions. The purpose of this study is to evaluate the relative effectiveness of each bolting pattern. A series of numerical models were created using Roc Science’s RS2. The models were based on a symmetrical section of the mine at its deepest point, and were modeled using generalized Hoek-Brown failure criterion along with a discrete fracture network. A series of sensitivity analyses were performed on the models by varying parameters such as joint friction angle, crack persistence, joint randomization, and tensile strength of the limestone. Based on the results of the original models and sensitivity analyses, it appeared that the standard bolting pattern provided sufficient roof support capacity under almost all the expected conditions at the mine, since safety factors below the design value of 1.5 were only found for individual bolts in a few of the worst test cases *** results can help improve the mine’s productivity and reduce operating costs without compromising safety.

关键词： Numerical modeling mining Roof bolting Roof stability Analysis RocScience’s RS2 Underground stone

modeling behaviors of a coal pillar rib using the progressive S-shaped yield criterion

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Journal of Rock mechanics and Geotechnical Engineering 2020年第3期12卷 484-492页

作者： Sankhaneel Sinha Gabriel walton Colorado School of mines GoldenCO80401USA

Spalling of pillar ribs has been a major hazard in the mining industry for *** the absence of rib support guidelines,accidents have continued to occur in recent *** effective support guidelines requires a complete understanding of complex pillar damage *** models represent a convenient tool for analyzing this problem,but the behavior of such models is dependent of the choice of the constitutive *** this study,a recently proposed constitutive model was used to simulate the rib fracturing process in a longwall chain pillar at West Cliff *** calibration,the model was able to capture the rib displacement profiles for multiple locations of the longwall face and the stress evolution 4 m into the *** rib bolts in the model were found to be yielding over 60% of their length under the headgate loading *** model also predicted a steady damage accumulation in the rib for certain face locations,which is consistent with the description of the rib at the *** was localized along the upper part of the pillar and underscored the role that the dirt band played in controlling rib deterioration at the *** ability of the numerical model to replicate field measurements provides confidence in the capabilities of the new constitutive ***,the need of using multi-point calibration is highlighted by comparing the results of the calibrated model to an alternative model calibrated to a smaller amount of data.

关键词： S-shaped yield criterion Coal pillar Back-analysis Numerical modeling

A DNA delivery system containing listeriolys in Oresults in enhanced hepatocytedirected gene expression

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World Journal of Gastroenterology 1999年第6期5卷 465-469页

作者： Cherie m. walton, Catherine H. Wu and George Y. Wu Department of medicine Division of Gastroenterology-Hepatology University of Connecticut Health Center Farmington CT United States Department of medicine Division of Gastroenterology-Hepatology University of Connecticut Health Center Farmington CT 06030 United States

AIm To determine whether incorporation of the pH dependent bacterial toxin listeriolysin O (LLO) into the DNA carrier system could increase the endosomal escape of internalized DNA and result gene expression. mETHODS A multi component delivery system was prepared consisting of asialoglycoprotein (ASG), poly L lysine (PL), and LLO. Two marker genes, luciferase and β galactosidase in plasmids were complexed and administered in vitro to Huh7[ASG receptor (+) ] and SK Hep1[ASG receptor (-) ] cells. Purity, hemolytic activity, gene expression, specificity, and toxicity were evaluated. RESULTS An LLO containing conjugate retained cell targeting specificity and membranolytic activity. In ASG receptor (+) cells, luciferase gene expression was enhanced by more than 7 fold over that of conjugates without the incorporation of listeriolysin O. No significant expression occurred in ASG receptor (-) cells. Enhancement of β galactosidase gene expression was less, but still significantly increased over controls. There was no detectable toxicity at concentrations shown to be effective in transfection studies. CONCLUSIONS ASOR PL can be coupled to LLO using disulfide bonds, and successfully target and increase the gene expression of foreign DNA.

关键词： DNA gene expression listeriolysin O hepatocytes

Validity of continuous-failure-state unloading triaxial tests as a means to estimate the residual strength of rocks

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Journal of Rock mechanics and Geotechnical Engineering 2021年第4期13卷 717-726页

作者： Gabriel walton Steven Gaines Leandro R.Alejano Department of Geology and Engineering Geology Colorado School of MinesGoldenCO80401USA Natural Resources Canada CanmetMININGOttawaOntarioK1A 1M1Canada Department of Natural Resources and Environmental Engineering Universidad de VigoVigo36310Spain

The residual strength of rocks and rock masses is an important parameter to be constrained for analysis and design purposes in many rock engineering applications.A residual strength envelope in principal stress space is typically developed using residual strength data obtained from compression tests on many different specimens of the same rock *** this study,we examined the potential for use of the continuous-failure-state testing concept as a means to constrain the residual strength envelope using a limited number of ***,cylindrical specimens of three rock types(granodiorite,diabase,and Stanstead granite)were unloaded at the residual state such that a full residual strength envelope for each individual specimen was *** a residual strength model that introduces a single new strength parameter(the residual strength index,or RSI),the results of the continuous-failurestate unloading tests were compared to conventionally obtained residual strength ***,the continuous-failure-state residual strength data were found to be consistent with the conventional residual strength ***,it was identified that the primary factor limiting an accurate characterization of the residual strength for a given rock type is not the amount of data for a given specimen,but the variety of specimens available to characterize the inherent variability of the rock unit of ***,the use of continuous-failure-state testing for estimation of the residual strength of a rock unit is only recommended when the number of specimens available for testing is very limited(i.e.<5).

关键词： Residual strength Continuous-failure-state testing Compression testing Brittle rock mechanics

Verification of a laboratory-based dilation model for in situ conditions using continuum models

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Journal of Rock mechanics and Geotechnical Engineering 2014年第6期6卷 522-534页

作者： G.walton m.S.Diederichs L.R.Alejano J.Arzúa Queen's University Kingston Canada University of Vigo Vigo Spain

With respect to constitutive models for continuum modeling applications, the post-yield domain remainsthe area of greatest uncertainty. Recent studies based on laboratory testing have led to thedevelopment of a number of models for brittle rock dilation, which account for both the plastic shearstrain and confining stress dependencies of this phenomenon. Although these models are useful inproviding an improved understanding of how dilatancy evolves during a compression test, there hasbeen relatively little work performed examining their validity for modeling brittle rock yield in situ. Inthis study, different constitutive models for rock dilation are reviewed and then tested, in the context of anumber of case studies, using a continuum finite-difference approach （FLAC）. The uncertainty associatedwith the modeling of brittle fracture localization is addressed, and the overall ability of mobilizeddilation models to replicate in situ deformation measurements and yield patterns is evaluated. 2014 Institute of Rock and Soil mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

关键词： Dilation Continuum models Case studies Brittle rock

Particle size dependent sinterability and magnetic properties of recycled HDDR Nd-Fe-B powders consolidated with spark plasma sintering

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Journal of Rare Earths 2020年第1期38卷 90-99页

作者： Awais Ikram Farhan mehmood Richard Stuart Sheridan muhammad Awais Allan walton Anas Eldosouky Saso Sturm Spomenka Kobe Kristina Zuzek Rozman Department for Nanostructured materials Jozef Stefan InstituteJamova 39SI-1000 LjubljanaSlovenia Jozef Stefan International Postgraduate School Jamova 39SI-1000 LjubljanaSlovenia School of metallurgy and materials University of BirminghamEdgbastonBirminghamB152TTUnited Kingdom magneti Ljubljana d.d.Stegne 37SI-1000 LjubljanaSlovenia

The dependence of the magnetic properties on the particle size of recycled HDDR Nd-Fe-B powders was investigated,with the aim to assess the reprocessing potential of the end-of-life scrap magnets via spark plasma sintering(SPS).The as received recycled HDDR powder has coercivity(Hci)=830 kA/m and particles in the range from 30 to 700 μm(average 220 μm).After burr milling,the average particle size is reduced to 120 μm and subsequently the Hci of fine(milled) powder was 595 kA/*** plasma sintering was exploited to consolidate the nanograined HDDR powders and limit the abnormal grain *** optimal SPS-ing of coarse HDDR powder at 750℃for 1 min produces fully dense magnets with Hci=950±100 kA/m which further increases to 1200 kA/m via thermal treatment at 750℃for 15 *** burr milled fine HDDR powder under similar SPS conditions and after thermal treatment results in Hci=940 kA/*** fine powder is further sieved down from 630 to less than 50 μm mesh size,to evaluate the possible reduction in Hci in relation to the particle *** gain in oxygen content doubles for m sized particles as compared with coarser fractions(>200 μm).The XRD analysis for fractionated powder indicates an increase in Nd2O3 phase peaks in the finer(m)***,the Hci reduces from 820 kA/m in the coarse particles(>200 μm) to 460 kA/m in the fine sized particles(m).SPS was done on each HDDR powder fraction under the optimal conditions to measure the variation in Hci and *** Hci of SPS-ed coarse fraction(>200 μm) is higher than 930 kA/m and it falls abruptly to just 70 kA/m for the fine sized particles(m).The thermal treatment further improves the Hci to>1000 kA/m only up to 100 μm sized fractions with>90% sintered *** full densification(>99%) is observed only in the coarse *** loss of coercivity and lack of sinterability in the fine sized particles(m) are attributed to a very high oxygen *** implies that durin

关键词： Reprocessing end-of life scrap Rare earth permanent magnets HDDR Nd2Fe14B Recycling Spark plasma sintering

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美国经济史

作者： (walton Gary m.)沃尔顿 (Rockoff Hugh)罗考夫

来源：南通市图书馆图书评论

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Health Quest 4.1

Corrigendum to “Verification of a laboratory-based dilation model for in situ conditions using continuum models” [J Rock mech Geotech Eng6 (2014) 522e534]

2003年

作者： Thomas D. Fahey Paul m. Insel walton T. Roth.

来源：畅想之星图书光盘版（南... 评论

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畅想之星图书光盘版（南通市图书馆镜像）

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Journal of Rock mechanics and Geotechnical Engineering 2017年第2期9卷 382-382页

作者： G. walton m.S. Diederichs L.R. Alejano J. Arzúa Queen’s University KingstonCanada University of Vigo VigoSpain

The authors regret that the photographic image in Fig. 4a of the published article was used in error, and therefore without proper referencing or permission from the originator or copyright holder. The image used in Fig. 4a of the original manuscript has been previously published by and remains under copyright by the Society for mining, metallurgy, and Exploration, Inc. (SmE) associated with the following *** S, Redmond S, Brox D, Procter P, Jezek D, van der Pouw Kraan m, Blanchet R, Kulka R. TBm Tunneling at the Ashlu Hydro Power Project, Squamish, BC. In: Almeraris G, mariucci B. editors. Proceedings of Rapid Excavation and Tunnelling 2009. The Society for mining,metallurgy, and Exploration, Inc. (SmE). 2009. pp. *** correct this error though this Corrigendum, Fig. 4 in this article is replaced with the following set of images. The caption remains unchanged from the original but is included here for convenience and clarity.

关键词： regret photographic manuscript