A dislocation-based approach to rock damage by blasting in underground mines.

摘要

Mine blast damage problems in near-field have received considerable attention in the past two decades, in contrast rock damage by cyclic loading in mid- to far-field regions has not been fully investigated. The effect of blast vibration on stability of underground excavations has only been considered empirically by peak particle velocity criterion.; This study is concerned with the rock damage problem by vibration through the theoretical and experimental investigation into rock cyclic loading. A new method to assess damage by cyclic loading to the rock in shear mode is proposed. In this study, the theory of dislocations is used to model rock plastic response ahead of a crack. Plastic displacement is determined within the crack plastic zone for a rock with a Ramberg-Osgood type representation of the mechanical behavior. In this work rock damage is investigated for one cycle of loading and unloading.; Monotonic and fatigue tests were carried out on granite specimens using a new single shear apparatus based on the Iosipescu method. These tests resulted in attainment of fatigue life (S-N) curve of granite.; The main outcome of this study is the development of a new numerical tool to assess rock damage by blast vibration. This tool provides a novel way to quantify vibration damage and predicts rock damage due to cyclic loading.; The model is capable of assessing damage in rock during cyclic loading with satisfactory accuracy. Results show that rocks containing large cracks are more susceptible to damage under vibration than those with small cracks. Moreover, while increase in the stress range increases damage to the rock, the rock response to such an increase is highly dependent on rock plastic behavior, and inherent crack size.; This research work is the first attempt to investigate rock damage by cyclic loading. The results are to be viewed as a first approximation to rock damage problem in mid- to far-field regions. Despite this, the results indicate that dislocation model can effectively be used to analyze blast damage in these regions. Once fully developed, the model can be integrated into the mine support design/selection processes for underground excavations.