| Description |
Modern mining systems frequently use drill and blast techniques for rock excavation. Rock blasting not only fragments rock but also creates overbreak in the rock surrounding the excavation. The unwanted damage often results in higher mining costs and severe safety concerns. To reduce unwanted damage, the ability to predict damage caused by rock blasting is essential. A shock wave based, engineer-friendly technique is developed in this dissertation. The design procedure is based on charts, graphs, and a computer program. The dissertation deals with three major aspects of developing a damage prediction model, namely, theoretical development, experimental research, and validation of the model using laboratory and field results. The theoretical development includes calculation of stress and response of rock for fully-coupled and decoupled blasting using the theory of shock wave transfer. This new procedure will be referred to as SWT. The objective is to use the properties of explosives and the properties of rock materials to develop a reasonable algorithm for predicting the extent of the damage zone caused by rock blasting. To validate the SWT model, three approaches are presented: (1) currently available experimental data in the literature; (2) large-scale laboratory experiments; and results of a field application in an underground mine. Based on Esen's (2003) laboratory experiments and large-scale laboratory experiments conducted as part of this dissertation, the SWT model successfully estimates the extent of the crush zone. Based on the work presented by Olsson (Olsson 1993) SWT provides reasonable estimates for the crack zone. Based on the comparison with other approaches, the SWT model is close to the Modified Ash (Energy-based), Modified Ash (Pressure-based), Holmberg Explosive Factor, and Sher Quasi-Static models. However, the crack zone did not conform to that observed in large scale laboratory models. The likely reason for this is the relatively small size of the laboratory models and lack of complete confinement. Application of this new method under field conditions, however, confirms the usefulness of SWT for practical blast design. Several new insights and useful information developed as a result of this research are valuable for the caution blast design at surface and underground mining. |
