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11	Progressive landslide analysis : Applications of a Finite Difference Method by Dr. Stig Bernander Case Study of the North Spur at Muskrat Falls, Labrador, Canada Dury, Robin January 2017 (has links) An easy-to-use spreadsheet version of a finite difference method for progressive landslide analysis has been developed. The finite difference method was originally developed by Dr. Stig Bernander, earlier adjunct professor at Luleå University of Technology and head of the Design Department of Skanska AB in Gothenburg, Sweden.. The so called Muskrat Falls Project consists in the ongoing construction of a hydroelectric power plant in Churchill River Valley, Labrador, Canada. The site hosting the project includes a land ridge which is supposed to be used as a natural dam and thus be submitted to important water pressures. Yet, previous landslides in the area have shown that a stability analysis is worth to be carried out in order to ensure the safety of the facility. Until now, investigations have only been carried out using the traditional limit equilibrium method and related elastic-plastic theory. For the sake of simplicity, this approach does not take into account deformations outside and inside the sliding body. However, because of the soil features in Churchill River Valley and particularly its ‘deformation softening’ behavior, there is increasing evidence that the conventional analysis is not relevant in this situation. Further, when analyzing the total stability of the ridge, only a horizontal failure surface has been used and not an inclined one, which is very optimistic and rather unrealistic.. In order to provide a more reliable study, a progressive failure analysis has been performed according to the finite difference method of Dr. Stig Bernander. The development of a spreadsheet adapted to this particular problem has allowed getting quickly and easily numerical results for several cases of study and assumptions. For assumed material properties and geometries of failure, the critical load-carrying capacity is below 1000 kN/m whereas a rise of the water level with 21 m will give an increased load of Nq = 2420 kN/m. This is more than twice of the what the ridge may stand with the assumed properties. The investigation has led to the conclusion that the situation will be risky for many combinations of soil properties if the water level is raised as high as initially planned. The investigation also shows that more material tests are necessary and that stabilization work may be needed to eliminate the risk for a landslide. Downhill progressive landslides Slope stability Sensitive clay Deformation softening Finite difference method Brittle failure in clay Liquefaction Muskrat Falls project Geotechnical Engineering Geoteknik
12	Investigation of the Pre to Post Peak Strength State and Behaviour of Confined Rock Masses Using Mine Induced Microseismicity Coulson, Adam Lee 01 March 2010 (has links) As hard rock mining progresses into higher stress mining conditions through either late stage extraction or mining at depth, the rock mass is driven not just to the peak strength, but often well into the post-peak until complete ‘failure’ occurs and easier mining conditions become evident. Limited research has been accomplished in identifying the transition of the rock mass and its behaviour into the post-peak and this research investigates this behaviour in detail. As the rock mass progressively fails, fractures are initiated through intact rock and extension and shear failure of these and pre-existing features occurs. Associated with this failure are microseismic events, which can be used to give an indication of the strength state of the rock mass. Based on an analogy to laboratory testing of intact rock and measurement of acoustic emissions, the microseismicity can be used to identify, fracture initiation, coalescence of fractures (yield), localization (peak-strength), accumulation of damage (post-peak) and ultimate failure (residual strength) leading to aseismic behaviour. The case studies presented in this thesis provide an opportunity to examine and analyse rock mass failure into the post-peak, through the regional and confined failures at the Williams and the Golden Giant mines, both in the Hemlo camp in Northern Ontario, Canada. At the Williams mine, the progressive failure of a sill pillar region into the post-peak was analysed; relating the seismic event density, combined with numerical modelling and a spatial and temporal examination of the principal components analysis (PCA), to characterize the extent, trend and state of the yielding zone, which formed a macrofracture shear structure. Observations of conventional displacement instrumentation, indicates regional dilation or shear of the rock mass occurs at or prior to the point of ‘disassociation’ (breakdown of stable PCA trends) when approaching the residual strength. At the Golden Giant mine, the complete process from initiation to aseismic behaviour is monitored in a highly stressed and confined pendent pillar. The PCA technique, numerical modelling and focal mechanism studies are used to define significant stages of the failure process, in which a similar macrofracture structure was formed. Temporal observations of key source parameters show significant changes prior to and at the point of coalescence and localization. Point of Disassociation PCA Analysis Microseismicity Post Peak Behaviour Strain Softening Behaviour Ductile Behaviour Seismic Source Parameters Fault Plane Solutions Brittle Damage Limits Hoek Brown Criteria Bulking Dilation Macrofracture Shear Zone SMART Cables MPBX Brittle Failure 0551 0428
13	Investigation of the Pre to Post Peak Strength State and Behaviour of Confined Rock Masses Using Mine Induced Microseismicity Coulson, Adam Lee 01 March 2010 (has links) As hard rock mining progresses into higher stress mining conditions through either late stage extraction or mining at depth, the rock mass is driven not just to the peak strength, but often well into the post-peak until complete ‘failure’ occurs and easier mining conditions become evident. Limited research has been accomplished in identifying the transition of the rock mass and its behaviour into the post-peak and this research investigates this behaviour in detail. As the rock mass progressively fails, fractures are initiated through intact rock and extension and shear failure of these and pre-existing features occurs. Associated with this failure are microseismic events, which can be used to give an indication of the strength state of the rock mass. Based on an analogy to laboratory testing of intact rock and measurement of acoustic emissions, the microseismicity can be used to identify, fracture initiation, coalescence of fractures (yield), localization (peak-strength), accumulation of damage (post-peak) and ultimate failure (residual strength) leading to aseismic behaviour. The case studies presented in this thesis provide an opportunity to examine and analyse rock mass failure into the post-peak, through the regional and confined failures at the Williams and the Golden Giant mines, both in the Hemlo camp in Northern Ontario, Canada. At the Williams mine, the progressive failure of a sill pillar region into the post-peak was analysed; relating the seismic event density, combined with numerical modelling and a spatial and temporal examination of the principal components analysis (PCA), to characterize the extent, trend and state of the yielding zone, which formed a macrofracture shear structure. Observations of conventional displacement instrumentation, indicates regional dilation or shear of the rock mass occurs at or prior to the point of ‘disassociation’ (breakdown of stable PCA trends) when approaching the residual strength. At the Golden Giant mine, the complete process from initiation to aseismic behaviour is monitored in a highly stressed and confined pendent pillar. The PCA technique, numerical modelling and focal mechanism studies are used to define significant stages of the failure process, in which a similar macrofracture structure was formed. Temporal observations of key source parameters show significant changes prior to and at the point of coalescence and localization. Point of Disassociation PCA Analysis Microseismicity Post Peak Behaviour Strain Softening Behaviour Ductile Behaviour Seismic Source Parameters Fault Plane Solutions Brittle Damage Limits Hoek Brown Criteria Bulking Dilation Macrofracture Shear Zone SMART Cables MPBX Brittle Failure 0551 0428
14	Rehabilitation of Exterior RC Beam-Column Joints using Web-Bonded FRP Sheets Mahini, Seyed Saeid Unknown Date (has links) In a Reinforced Concrete (RC) building subjected to lateral loads such as earthquake and wind pressure, the beam to column joints constitute one of the critical regions, especially the exterior ones, and they must be designed and detailed to dissipate large amounts of energy without a significant loss of, strength, stiffness and ductility. This would be achieved when the beam-column joints are designed in such a way that the plastic hinges form at a distance away from the column face and the joint region remain elastic. In existing frames, an easy and practical way to implement this behaviour following the accepted design philosophy of the strong-column weak-beam concept is the use a Fibre Reinforced Plastic (FRP) retrofitting system. In the case of damaged buildings, this can be achieved through a FRP repairing system. In the experimental part of this study, seven scaled down exterior subassemblies were tested under monotonic or cyclic loads. All specimens were designed following the strong-column weak-beam principal. The three categories selected for this investigation included the FRP-repaired and FRP-retrofitted specimens under monotonic loads and FRP-retrofitted specimen under cyclic loads. All repairing/retrofitting was performed using a new technique called a web-bonded FRP system, which was developed for the first time in the current study. On the basis of test results, it was concluded that the FRP repairing/retrofitting system can restore/upgrade the integrity of the joint, keeping/upgrading its strength, stiffness and ductility, and shifting the plastic hinges from the column face toward the beam in such a way that the joint remains elastic. In the analytical part of this study, a closed-form solution was developed in order to predict the physical behaviour of the repaired/retrofitted specimens. Firstly, an analytical model was developed to calculate the ultimate moment capacity of the web-bonded FRP sections considering two failure modes, FRP rupture and tension failure, followed by an extended formulation for estimating the beam-tip displacement. Based on the analytical model and the extended formulation, failure mechanisms of the test specimens were implemented into a computer program to facilitate the calculations. All seven subassemblies were analysed using this program, and the results were found to be in good agreement with those obtained from experimental study. Design curves were also developed to be used by practicing engineers. In the numerical part of this study, all specimens were analysed by a nonlinear finite element method using ANSYS software. Numerical analysis was performed for three purposes: to calculate the first yield load of the specimens in order to manage the tests; to investigate the ability of the web-bonded FRP system to relocate the plastic hinge from the column face toward the beam; and to calibrate and confirm the results obtained from the experiments. It was concluded that numerical analysis using ANSYS could be considered as a practical tool in the design of the web-bonded FRP beam-column joints. Reinforced concrete Reinforcement Bar strong-column weak-beam principal Exterior Beam-Column Joints Core Small scale modelling Experimental Test set-up Control Plain specimen Rehabilitation Retrofitting retrofitted Repair Repaired Repairing Strengthening Controlling Relocating Plastic hinge Pre-cracking Cracking Crushing Post-cracking Crack Cracked Penetration Damaged Pre-cracked Web-Bonded Wrapping De-bonding Fibre Reinforced Plastic FRP Sheets Composite Confinement Monotonic loads Cyclic loading Loads Displacement control Load control Regime Phase Loading sequence Procedure Available ductility factor Curvature ductility factor Ultimate First yield Flexural yielding Strength Moment Stiffness Failure mechanism Modes Sudden Brittle failure Measured beam-tip displacement Deflection Numerical analysis ANSYS Solid65 Solid45 Link8 Non-linear Finite Element (FE) Convergence criteria Analytical Closed from FRP rupture tension failure Compression failure Minimum thickness Maximum thickness Compressive Tensile Steel Ratio Design charts Effective Moment of Inertia Compatibility Strain Stress

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