GPGPU-parallelised hybrid finite-discrete element modelling of rock chipping and fragmentation process in mechanical cutting

Mechanical cutting provides one of the most flexible and environmentally friendly excavation methods.It has attracted numerous efforts to model the rock chipping and fragmentation process, especially usingthe explicit finite element method (FEM) and bonded particle model (BPM), in order to improve cuttingefficiency. This study investigates the application of a general-purpose graphic-processing-unit parallelised hybrid finite-discrete element method (FDEM) which enjoys the advantages of both explicit FEMand BPM, in modelling the rock chipping and fragmentation process in the rock scratch test of mechanical rock cutting. The input parameters of FDEM are determined through a calibration procedure ofmodelling conventional Brazilian tensile and uniaxial compressive tests of limestone. A series of scratchtests with various cutting velocities, cutter rake angles and cutting depths is then modelled using FDEMwith calibrated input parameters. A few cycles of cutter/rock interactions, including their engagementand detachment process, are modelled for each case, which is conducted for the first time to the bestknowledge of the authors, thanks to the general purpose graphic processing units (GPGPU) parallelisation. The failure mechanism, cutting force, chipping morphology and effect of various factors on themare discussed on the basis of the modelled results. Finally, it is concluded that GPGPU-parallelised FDEMprovides a powerful tool to further study rock cutting and improve cutting efficiencies since it canexplicitly capture different fracture mechanisms contributing to the rock chipping as well as chip formation and the separation process in mechanical cutting. Moreover, it is concluded that chipping ismostly owed to the mix-mode I-II fracture in all cases although mode II cracks and mode I cracks are thedominant failures in rock cutting with shallow and deep cutting depths, respectively. The chipmorphology is found to be a function of cutter velocity, cutting depth and cutter rake angle