Studies on comminution.

The physical quantity of the square of tensile strength over Young’s modulus has been proposed as a criterion of comminution of rock by Oka and Majima. The value was determined for five different rocks, measuring tensile strength and Young's modulus. The testing method used to determine both rock properties was a point-load tensile strength test and measurement of propagation velocity of P-wave. In order to verify the applicability of the criterion thus obtained, the drop-weight impact test and ball mill grinding were carried out using the identical specimen used for tensile strength and Young's modulus test. The experimental result was obtained that the square of tensile strength is more applicable than the square of tensile strength over Young's modulus. In chapter 2, grinding tests were performed with a 12 inch batch mill. A torque meter was installed to estimate the energy consumption.necessary to achieve size reduction. From the torque measurement, the required torque for the mill turning remained almost constant regardless of the material being ground. A new concept, Energy Index, was introduced to evaluate grinding results and to study grinding problems. For each rock sample tested, the energy index was determined from torque measurements and the quantity of the products. It was found the energy index has a linear relationship with Bond work index under selected grinding condition.Applied Science, Faculty ofMining Engineering, Keevil Institute ofGraduat