UBC Theses and Dissertations

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UBC Theses and Dissertations

Rock fall engineering : development and calibration of an improved model for analysis of rock fall hazards on highways and railways Wyllie, Duncan C.


My research on rock falls over the last five years is an extension of my 45 year professional career that has included a wide variety of rock fall projects. This experience has provided me with an excellent understanding of rock fall behavior; the objective of my research has been to apply this to developing improvements in rock fall modeling methods and design of rock fall containment structures. My research to meet these objectives has involved the following: Case studies – details of rock fall behavior at six locations with varied topography and geology are presented, and the results have been used to verify the application of impact mechanics theory to rock falls, and to calibrate modeling programs. Rock fall trajectories and velocities – the application of Newtonian mechanics to rock fall trajectories and velocities is described, and results compared with actual translational and angular velocities, and trajectory heights. Impact mechanics – the application of theoretical impact mechanics to rock fall impacts is discussed in terms of [normal impulse – relative velocity] diagrams for rough, rotating bodies, and equations relating impact and restitution velocities and angles. Coefficient of restitution – it is shown that the normal coefficient of restitution defined by the normal final and impact velocities is related primarily to impact angle rather than slope material properties. Furthermore, for shallow impact angles less than about 20 degrees, the normal coefficient of restitution can be greater than 1.0. Energy changes – energy is lost during impact and gained during trajectories. Equations for energy changes are developed, as well as diagrams showing values of changing potential, kinetic and angular energies during rock falls. Rock fall modeling – results of rock fall modeling using the RocScience program RocFall 4.0 for five case studies are presented; the applicable input parameters are listed. Design of protection structures –impact mechanics and scale model tests of protection nets show that these structures can be designed to redirect rather than stop rock falls, and to absorb energy uniformly during impact. These properties mean that only a portion of the impact energy is absorbed by the net and that forces induced in the net are minimized.

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