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Journal of Rock Mechanics and Geotechnical Engineering 2019年第5期11卷 909-919页

作者： Philippe Morissette john hadjigeorgiou Agnico Eagle Mines Limited 10 200route de PreissacRouyn-NorandaJ0Y 1C0Canada University of Toronto TorontoM5S 3E3Canada

There are considerable challenges associated with the design of ground support for seismically-active underground *** is extremely difficult to establish the demand on ground support as well as the capacity of a ground support *** resulting dynamic or impact loads caused by mining-induced seismicity are difficult to anticipate and *** performance of a ground support system is defined by the load distribution and interaction between several reinforcement and surface support ***,the design of ground support in seismically-active mines tends to evolve,or be modified based on qualitative assessments of perceived performance or response to significant seismic events or *** research is motivated by a need to provide quantitative and data-driven design guidelines for ground support systems subjected to dynamic-loading *** data were collected from three deep and seismically-active underground mines in the Sudbury basin in *** constructed database comprises 209 seismic events that resulted in damage to mine excavations and ground *** events were associated with damage at 324 locations within the three *** developed ground support design strategy,based on these documented case studies,identifies areas where the use of dynamic or enhanced support should be *** developed design methodology provides guidelines for the zoning of mine locations in which installation of enhanced support is recommended,the specifications for an optimal ground support system,and the timing or sequence of installation.

关键词： Ground support design Mining-induced seismicity Rockburst

Explicit reinforcement models for fully-grouted rebar rock bolts

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第2期9卷 267-280页

作者： Navid Bahrani john hadjigeorgiou Lassonde Institute of Mining University of TorontoTorontoM5S 1A4Canada

This paper investigates the explicit use of rock reinforcement in a discontinuous stress analysis model.A series of numerical experiments was undertaken to evaluate the performance of local and global reinforcement models implemented in universal distinct element code(UDEC).This was made possible by calibrating the reinforcement models to the laboratory behavior of a fully-grouted rebar bolt tested under pure pull and pure shear loading *** model calibration focuses on matching different loading stages of the force-displacement curve including the initial elastic response,the hardening behavior and the bolt *** paper concludes with a discussion on the suitability of the different reinforcement models in UDEC including their advantages and ***,it addresses the choice of input parameters required for a realistic simulation of fully-grouted rebar bolts.

关键词： Rock reinforcement Fully-grouted rebar Distinct element method Local reinforcement Global reinforcement Pull-out test Shear test

Responses of jointed rock masses subjected to impact loading

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Journal of Rock Mechanics and Geotechnical Engineering 2018年第4期10卷 624-634页

作者： Shabnam Aziznejad Kamran Esmaieli john hadjigeorgiou Denis Labrie Lassonde Institute of Mining University of Toronto CanmetMINING Natural Resources Canada

Impact-induced damage to jointed rock masses has important consequences in various mining and civil engineering applications. This paper reports a numerical investigation to address the responses of jointed rock masses subjected to impact loading. It also focuses on the static and dynamic properties of an intact rock derived from a series of laboratory tests on meta-sandstone samples from a quarry in Nova Scotia, Canada. A distinct element code(PFC2D) was used to generate a bonded particle model(BPM) to simulate both the static and dynamic properties of the intact rock. The calibrated BPM was then used to construct large-scale jointed rock mass samples by incorporating discrete joint networks of multiple joint intensities into the intact rock matrix represented by the BPM. Finally, the impact-induced damage inflicted by a rigid projectile particle on the jointed rock mass samples was determined through the use of the numerical model. The simulation results show that joints play an important role in the impactinduced rock mass damage where higher joint intensity results in more damage to the rock mass. This is mainly attributed to variations of stress wave propagation in jointed rock masses as compared to intact rock devoid of joints.

关键词： Jointed rock mass Impact loading Microcracks Rock damage

Performance of identical rockbolts tested on four dynamic testing rigs employing the direct impact method

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Journal of Rock Mechanics and Geotechnical Engineering 2021年第4期13卷 745-754页

作者： Charlie C.Li john hadjigeorgiou Peter Mikula Greig Knox Bradley Darlington Renee Royer Andrzej Pytlik Michael Hosp Norwegian University of Science and Technology(NTNU) TrondheimNorway University of Toronto TorontoCanada Mikula Geotechnics Pty.Ltd. KalgoorlieAustralia New Concept Mining JohannesburgSouth Africa Sandvik Mining&Rock Technology HeatherbraeAustralia CanmetMINING Natural Resources CanadaOttawaCanada Central Mining Institute KatowicePoland Minova Innovation and Development Ground SupportFeistritzAustria

Impact drop tests are routinely used to examine the dynamic performance of *** impact tests have been carried out in the past decades on independently designed,constructed and operated testing *** laboratory has developed testing procedures;thus,the results are often reported in different ways by various *** inconsistency in testing procedures and reporting formats presents a challenge when comparing results from different laboratories.A series of impact tests of identical rockbolts was carried out using the direct impact method(*** mass free-fall method)on the rigs in four laboratories in different *** purpose of these tests was to investigate the level of consistency in the results from the four *** rig demonstrated a high level of repeatability,but differences existed between the various *** differences would suggest that there is noticeable equipment-dependent bias when test results obtained from different laboratories are *** was also observed that the energy dissipated for the plastic displacement of the bolt was smaller than the impact energy in the *** average impact load(AIL)and the ultimate plastic displacement(D)of the bolt describe the ultimate dynamic performance of the *** the case where the bolt does not rupture,the specific plastic energy(SPE)is an appropriate parameter in describing the impact performance of the *** other relevant parameters are the first peak load(FPL)and the initial stiffness(K)of the bolt *** information from this test series will guide the formulation of standardised testing procedures for dynamic impact tests of rockbolts.

关键词： Dynamic test Drop test Impact test Rockbolt Rock reinforcement Ground support

Restless legs syndrome is contributing to fatigue and low quality of life levels in hemodialysis patients

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World Journal of Nephrology 2017年第5期6卷 236-242页

作者： Christoforos D Giannaki Michael Hadjigavriel Akis Lazarou Aristos Michael Loukas Damianou Efthimios Atmatzidis Ioannis Stefanidis Georgios M hadjigeorgiou Giorgos K Sakkas Marios Pantzaris Department of Life and Health Sciences University of NicosiaNicosia CY 1700Cyprus the Cyprus Institute of Neurology and Genetics Nicosia CY 1683Cyprus Hemodialysis Unit Larnaca General HospitalLarnaca CY 6021Cyprus Hemodialysis Unit Limassol General HospitalLimassol CY 3304Cyprus School of Medicine University of Thessaly41110 LarisaGreece Faculty of Sport and Health Sciences University of St Mark and St JohnPlymouth PL6 8BHUnited Kingdom

AIM To examine whether hemodialysis(HD) patients with restless legs syndrome(RLS) are subjects of greater fatigue and impaired quality of life(QoL) compared to HD patients without *** Eighty five stable HD patients participated in this study. According to their RLS status, the patients were dividedinto the RLS group(n = 23) and the non-RLS group(n = 62). QoL, fatigue, sleep quality, daily sleepiness and depression symptoms were assessed by using various questionnaires. Finally, biochemical parameters including iron, ferritin, hemoglobin, hematocrit and parathormone were assessed. RESULTS The HD patients with RLS scored worse in all the questionnaires used in the study(P < 0.05). The patients with RLS were more likely to receive the HD therapy on the morning shift, whilst 43.5% of the RLS patients reported to experience the RLS symptoms also during HD. The severity of RLS was correlated with fatigue, depression score and sleep quality(P < 0.05). CONCLUSION HD patients with RLS are subject to lower QoL related parameters and greater fatigue compared to HD patients without RLS. RLS should be successfully managed in order to improve the QoL of the sufferers.

关键词： Sleep quality Depression Secondary restless legs syndrome Fatigue Quality of life