Mechanical rock breakage has been of interest in modern mining and civil construction industries for decades now. However, the rock fracture mechanism associated with rock cutting processes is not yet well understood due to complex interaction between the cutter and the rock. With recent advances in numerical simulation methods, these techniques have become powerful tools for investigating the early rock fracturing process. However, not all numerical modelling methods are able to simulate this process correctly. This paper uses a new extension of combined finite-discreet element method to simulate the mechanical rock breakage with a simple drag cutting tool. The modelling technique takes into account the mix-mode I-II fracture criteria in addition to mode I and mode II for predicting the initiation and propagation of the cracks. After calibration of input parameters against uniaxial compressive and Brazilian tensile strength tests, tool-rock interaction is simulated in three different cutting velocities.

1 Introduction

During recent decades, the application of mechanical breakage tools in rock fragmentation has been widely extended to mining and civil engineering industries. Mechanical excavation machines provide a more flexible and environmentally friendly alternative to conventional blasting, especially in urban or non-ventilated environments.

Typically, there are two types of rock cutting methods classified based on the moving direction of the mechanical tool with respect to the rock surface: drag cutters (or fixed cutter bits) and indenters. While a drag cutter hits the rock in a direction parallel to the rock surface, the indenter penetrates normal into the rock surface (Hood and Alehossein, 2000). Rock cutting experiments are largely used to investigate the cutting process and the associated cutting forces; however, due to the extensive number of factors that influence the cutting process, the application of experiments to study the effective parameters can become expensive. Meanwhile, analytical and empirical methods developed so far suffer from too many simplistic assumptions. Over the years, different numerical techniques have been considered for investigation of rock fracture process with a cutting tool; however, not all the numerical techniques are able to model the entire rock cutting process (Menezes, 2016). Hence, despite many researches, the rock fragmentation mechanism with a mechanical cutter has not been well understood due to the complexity of the interaction between mechanical tool and rock, and complex rock fracture process (Che et al., 2016). In recent years, however, new advancements in numerical modelling methods have significantly improved their potential for simulating the complex rock failure mechanisms. This paper aims to investigate the rock cutting process with a simple drag tool using a new implementation of combined finite-discrete element method (FDEM). The presented FDEM code uses parallel computation enabled by general purpose graphic processing units (GPGPU). This capability significantly speeds up the computations, which makes the code suitable for simulating time-consuming processes involved in rock cutting.

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