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Jefferies M.,Klohn Crippen Berger | Rogers B.,Wright Inc. | Hardy M.,Wright Inc. | Wright B.,Wright Inc.
Proceedings of the International Conference on Port and Ocean Engineering under Arctic Conditions, POAC

The Molikpaq deployment at Amauligak I-65 (ept/85-July/86) provides important data on icestructure interaction, for broad structures, because of the magnitude and type of interactions experienced. Although studied in depth twenty five years ago, the data has come into recent focus with further studies for development of the Amauligak discovery. But, what has become obscured and/or forgotten after twenty five years is the way ice loads on the Molikpaq were measured and recorded - There is both more detail and greater accuracy than apparently appreciated, but also limitations because of shortfalls in measurements during the first part of that winter. This paper describes the instrumentation and data acquisition systems installed in 1983-4, the upgrading of the instrumentation during 1986, and summarizes the extensive calibration work subsequently undertaken during 1986-9. An example of the measured ice loads is presented for a complete event (12 May 86) for which particularly simple conditions allow an independent assessment of ice load magnitude. The uncertainties in measured ice loads are discussed. Copyright © (2011) by Port and Ocean Engineering under Arctic Conditions (POAC 2011). Source

Hungr N.,CNRS Complex Medical Engineering Laboratory | Roger B.,Klohn Crippen Berger | Hodgson A.J.,University of British Columbia | Plaskos C.,OMNIlife science
IEEE Transactions on Haptics

In this paper, we present a novel haptic technique for emulating hard surfaces with high realism; such a technique has significant potential utility in certain orthopedic surgery applications such as joint replacement surgery where the goal is to prevent incursions beyond a virtual surface during bone cutting operations. The Dynamic Physical Constraint (DPC) concept uses a unidirectional physical constraint that is actively positioned to limit movement between two manipulator links; the concept is applicable to providing virtual constraints in both 2D and 3D workspaces. Simulation results demonstrate the potential feasibility of the concept, and a prototype device was built for testing. The DPC device provides a convincing sensation of a real, hard virtual surface which can be smoothly tracked when the end effector is in contact with the surface. Incursion across the surface with the prototype was well submillimetric and within the accuracy constraints required for joint replacement applications. © 2012 IEEE. Source

Ghafghazi M.,University of California at Davis | Shuttle D.A.,Klohn Crippen Berger | DeJong J.T.,University of California at Davis
Soils and Foundations

Soil particles break during shear, with the intensity of the breakage depending on the stress level amongst other factors. Particle breakage has important implications for the soil's critical state, which is an input to the majority of advanced constitutive models. This work examines a micromechanical framework where particle breakage shifts down the critical state locus in void ratio versus mean effective stress space without changing its slope. The framework assumes that detectable particle breakage in sand does not occur unless the contraction potential of the material, solely by the sliding and the rolling of the particles, is exhausted and a soil specific stress level threshold is surpassed. A series of triaxial compression tests conducted to investigate the validity of the framework is presented. It is shown that particle breakage is a factor, working alongside dilatancy, imposing additional compressibility on the soil. © 2014 The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved. Source

Tuckey Z.,Simon Fraser University | Stead D.,Simon Fraser University | Sturzenegger M.,Klohn Crippen Berger | Elmo D.,Golder Associates | Terbrugge P.,SRK Consulting
46th US Rock Mechanics / Geomechanics Symposium 2012

Despite over four decades of research into rock mass and discontinuity characterization, there are still no standardized methods for field characterization of discontinuity persistence and in particular intact rock bridges. As part of an ongoing project at Simon Fraser University, three open pit mines and one natural slope were investigated using digital photogrammetry, ground-based LiDAR, and modified discontinuity survey methods. The investigation had the specific objective of assessing discontinuity persistence and potential for intact rock bridges. Discontinuity surveys were carried out on 3-dimensional terrain models and on 2-dimensional trace maps at bench, inter-ramp, and overall pit slope scales. Modifications to the field methodology were trialed based on contrasts in lithology, bench condition, and structural environments at the four sites. The results are being used to develop preliminary recommendations for an adaptable methodology for assessing discontinuity persistence and intact rock bridge content, which may be customized according to site-specific requirements, geological conditions, and the tools available to the practitioner. Copyright 2012 ARMA, American Rock Mechanics Association. Source

Sosio R.,University of Milan Bicocca | Crosta G.B.,University of Milan Bicocca | Chen J.H.,Klohn Crippen Berger | Hungr O.,University of British Columbia
Quaternary Science Reviews

Ice-rock avalanches which occur in glacial environments are controlled by the presence of snow and ice in the moving material and by possible propagation onto icy basal surfaces. All these factors contribute to enhancing the flow mobility. Mixing with ice and snow hampers block collisions and favours dense flow behaviour. Ice melting reduces granular friction by saturation of the basal material and fluidization effects. Propagating onto glaciers offers a smooth surface with low shear resistance. This work is a review of the best documented ice-rock avalanches and focuses on evaluating their mobility for hazard analysis purposes by providing a set of calibrated cases. The rock avalanches have volumes ranging from 5*10 6 m 3 to 25*10 6 m 3. We replicate these events by using SPH and FEM numerical methods, assuming frictional and Voellmy basal rheologies. The Voellmy rheology best performs at replicating the landslide propagation. Among the back analyzed cases, the frictional coefficient ranges in the interval 0.03-0.1, the turbulent coefficient within 1000 m s -2-2000 m s -2. The bulk basal friction angle ranges within 2.75° and 14° with values inversely related to event volumes. Forward selection of the basal friction angle based on event volume, allows the replication of the Mount Cook ice-rock avalanche predicting a maximum runout which is less than 4% larger than observed. In the perspective of forward modelling, large uncertainty is related to the reconstruction of the post-event topographies, particularly for the sliding surface. Mixing with ice and snow reduces basal friction proportionally to ice and snow content. Pure ice has a basal friction which is reduced by about 75% than basal friction of pure rock. Melting of ice during rock avalanche propagation has been evaluated for the Sherman event. The frictional heat generated at the glacier surface results in the melting of 86.2 ± 5.9 kg m -2, which could have contributed to a minimum 20-35% (±10%) reduction of the material friction angle through the sole pore pressure generation within a 40 and 20 cm thick shear layer, respectively. The largest uncertainty is related to the area of contact between rock and ice. © 2012 Elsevier Ltd. Source

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