Date of Graduation


Document Type



Efficient rock breakage is a result of optimum use of available resources in a continuous mining system. Research demonstrates that specific respirable dust must be kept at a minimum in order to produce the optimum parameters of rock breakage process. A cutting process that induces large chips of cut product results in minimum respirable dust. To produce larger chips of cut product, a correct inter-play of several bit geometry related parameters is essential. As the ridges/lands between two adjacent grooves are removed, a free surface is available for subsequent cuts. The nature of ridge failure is a function of the bit geometry parameters and is demonstrative of the extent of respirable dust generated. The study carried out in this dissertation investigates the influence of four different bit geometry parameters on specific respirable dust during rock cutting. The exact breakage and failure characteristics of rock are difficult to determine. Ridge/land failure being the source of the dust produced an exact mechanism to understand the cutting process and rock response under dynamic action is necessary. Most often, it is assumed that the rock chips are formed along the pre-existing cleats and fractures in the rock mass. If there are pre-existing fractures in the rock mass, the ridge formation and removal becomes easier with minimum expense of the available resources. A good understanding of the ridge failure nature will provide a basis for efficient rock breakage. In this study, the dynamic cutting conditions were simulated using a shear test rig in the laboratory. The shear strength of rock obtained using the dynamic test rig is analyzed as a function of loading rate, and in the context of rock cutting conditions. A normalized shear load factor (NSLF) is developed as a function of the shear load component of the applied force on the cutting bits and the shear strength of the rock. The breakout angle during the ridge failure is investigated. The breakout angle during the rock cutting is compared and contrasted with the failure angle obtained in a triaxial test case. Finally, a graphical model/nomogram incorporating the normalized shear load factor and the specific respirable dust is developed.