Abstract:

Numerical methods are becoming more attractive for modeling complex rock-tool interaction processes as idealized analytical methods with simplified assumptions do not fully capture the failure process. In this paper, a two-dimensional particle flow code and boundary element code were used to help understand the rock-cutting process in drag cutting mode. In particle flow code, the micro-parameters such as particle/grain size, particle size distribution (to account for rock heterogeneity), contact bond strength and stiffness between the particles/grains were determined by calibrating the model against known properties of Harcourt granite. The numerical simulation results have indicated crushing beneath the tip of the drag cutter, and propagation of distinct cracks further ahead towards the edge of the sample forming a rock chip. It has been observed that for small depth of cut, the rock chipping process is governed by the formation of large number of tensile cracks. However, further experiments are needed in various rock formations to gain clear understanding of fracturing mechanism of rock at different depth of cuts.

1 INTRODUCTION

The advantage of rock excavation by mechanical means, over conventional drilling and blasting methods, has been realized over the years in terms of safety, automation, dilution control and contour excavation. The mechanism of rock cutting by mechanical tools such as indenters, drag bits, rolling and oscillating cutters have not been fully explored and understood yet. This is partly because of the inherent nature of rock, and partly because of the complex process of rock cutting. A detailed understanding of micro-mechanics of the rock chipping process is vital in understanding of tool wear. The tool wear affects the economics of the cutting process, and its minimization depends on the type of tool material and its geometry and on the underlying friction between the tool and the rock.

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