Aziznejad, S. and Esmaieli, K. 2015. Effects of joint intensity on rock fragmentation by impact, 11th International Symposium on Rock Fragmentation by Blasting, 24-26 August, Sydney, Australia

Abstract

Impact-induced rock fragmentation is a mechanism that is commonly used for rock breakage in drilling and crushing. Additionally, rock fragmentation by blasting is frequently used in rock excavation operations. Experience shows that presence of discontinuities in rock can significantly influence the impact-induced damage and fragmentation of rock. Quantification of the response of jointed rock masses to impact loads is complicated by the fact that the available laboratory tests are mainly designed for aggregates or intact rocks. It can be argued that neither of these tests adequately represent a jointed rock mass. This paper presents the results of a series of numerical simulations used to investigate the influence of pre-existing discontinuities on the impact-induced fragmentation of rock masses. The methodology includes determination of the static and dynamic mechanical properties of a rock unit by conducting a series of laboratory tests on intact rock samples collected from a quarry in Canada. A 2D distinct element code, Particle Flow Code (PFC2D), was used to generate a bonded particle model in order to simulate both static mechanical properties (Uniaxial Compressive Strength, Elastic Modulus, Poisson’s Ratio and indirect Tensile Strength) and dynamic mechanical property (drop weight tensile strength) of the intact rock. The calibrated numerical model was then used to construct large-scale synthetic rock mass samples by incorporating discontinuity networks of different intensity into the bonded particle model. Finally, the impact-induced fragmentation inflicted by a rigid projectile particle on the jointed rock mass samples, simulated by a synthetic rock mass model, was determined. More fragmentation was observed for the rock mass samples with higher joint intensity.