| In the context of this thesis, the energy absorption capacity of a prototype tendon support system was tested using an impact-testing rig on Noranda Inc.'s Technology Centre premises. The verification tests done on the Modified Cone Bolt (MCB) prototype support system in quasi-static and impact loading modes was also used to propose a displacement evaluation method for tendons submitted to impact loading. It relies on parameters that can be extracted from pull out tests, which can be easily performed underground. Velocity damping is introduced in the reaction of the tendon as well as other means of energy dissipation through the use of a critically damped harmonic motion system. It was found that results from the proposed calculation method were consistent with laboratory investigations. The input parameters for the calculation method are the plastic stiffness of the support system and its yield point, as obtained from pull out testing. By choosing the tendon burden and ejection velocity, one can calculate the displacement of the tendon as well as its axial load through time. Because the complete load-displacement characteristic curve is available with the calculations, one can estimate the work energy dissipation during the impact loading of the tendon support system for a given tendon burden and ejection velocity. This could help for case analysis in areas damaged by seismicity, as well as for the determination of bolt spacing given a probable depth of failure and an arbitrary velocity of ejection range. (Abstract shortened by UMI.)... |
