Abstract

An understanding of the fragmentation of rock blocks from gravity free-fall has applications to rock fall analysis as well as block cave mining. In the case of a rock fall, blocks splitting mechanics can reduce the overall block energy and therefore reduce the travel distance of the blocks. Conversely, splitting may result in a larger number of smaller fragments that may still pose a risk despite their reduced dimensions. In the case of block caving, splitting of blocks it is believed to aid the flow of the ore column, to reduce the potential of hang-ups, and to allow for easier extraction and processing of the ore. Traditional methods for block fragmentation analysis use empirical relationships and rule-based approaches that heavily rely on the block geometry, rather than block-to-block interactions. In this paper we present a study of fragmentation processes using a hybrid finite-element/discrete-element method (FEM/DEM). The approach is capable to account for the numerical instability generally associated with the simulation of high velocity surface interactions and subsequent fracturing. To date the analysis has focused on the simulation of free-falling blocks onto a fixed surface. The initial and final block breakage has been compared against parameters including the roughness and curvature of the impacted surface, and the rock block orientation in space during free fall. We believe the results could provide useful insight into designing catchments for rock fall, as well as an increased understanding of the complexities of secondary fragmentation estimates and the range of fragmentation that could be expected in block caving.

Introduction

The breakage of rock blocks, also called fragmentation, is an important concept in many aspects of rock engineering including rock fall analysis and block cave mining. The fragmentation of a rock block during rock fall can reduce the overall block energy and reduce the travel distance of resultant subblocks; however, splitting blocks results in more fragments with trajectories that are difficult to predict [1]. The expected fragmentation of a block cave mine is a key decision parameter when determining the feasibility of such projects [2]. The reduced block size due to block splitting may aid in the flow of the ore column and reduce the potential for rock blocks to obstruct drawpoints (hang-ups) and smaller rock blocks are also easier and more cost-effective to transport and process. [3].

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