Fragmentation characteristics and energy components of non-cylindrical rock specimens in a novel collision system

Abstract

This paper presents the results of rock fragmentation by using a new collision method we reported earlier. Since the method has been proved to be successful for cylindrical rock specimens in our earlier papers, this paper presents the results from 28 non-cylindrical rock specimens such as half-cylinders and half-discs. The results show that: (1) all rock specimens were successfully released at a flight velocity of 13.7 – 62.5 m/s, validated the method for non-cylindrical specimens. (2) All specimens were broken into various sizes of fragments (particles). (3) The energy transferred to the transmitted bar was in a range of 0.3 – 3.4 % of input energy. (4) The translational kinetic energy of rock specimen was in a range of 0.1 – 18.9 % of input energy, while the rotational kinetic energy of rock specimen was 3.3 –5.1 % of input energy. (6) The specific input energy (input energy per unit volume of rock) varied from 0.26 to 5.06 MJ/m³. (7) The main factors influencing rock fragmentation include specific input energy, rock impedance and foliations. Larger specific input energy or smaller impedance resulted in better fragmentation, and vice versa. Foliations, especially parallel ones, made spalling occurred in most quartzite specimens as well as a few other rock specimens before they collided with the transmitted bar. Assuming that relative energy efficiency is equal to the ratio of the energy absorbed by rock to the input energy, the paper finds that the relative energy efficiency of the rock collision method is much higher than the relative energy efficiencies of dynamic rock compression, dynamic rock fracture, and ore grinding in ball mills, indicating a great potential of applying the collision method to mining industry.