GPGPU-Based 3-D hybrid FEM/DEM for numerical modelling of various rock testing methods

In the field of geotechnical engineering, the number of applications of combined/hybrid finite-discrete-element method (HFDEM) to both the lab-scale and field-scale problems has increased recently. In author’s research group at university of Tasmania, 2-D/3-D HFDEM code has also been successfully developed [e.g. Liu et al. 2015, Int. J. Geotech. Eng. 9:115-131] and applied to some geotechnical engineering problems such as rock blasting, fracture processes in a series of lab-scale rock testing methods and asperity degradation and gouge grinding during direct shearing of rough rock joints. However, since the HFDEM code was implemented by sequential programming, its main application mentioned above was limited to 2-D problems owing to the computationally expensive nature of HFDEM. To overcome this situation, the parallel programming scheme using “general-purpose-graphic-processing-unit (GPGPU)” and “CUDA (Compute Unified Device Architecture) C” was recently incorporated into the HFDEM code and significant speed-up has been achieved. This paper briefly describes the theory and newly incorporated features of the GPGPU-based HFDEM code along with some important issues which have not been addressed clearly in the previous publications using HFDEM. Then, this paper demonstrates some examples of 3-D numerical modelling of rock fracture process using various lab-scale rock testing methods such as quasi-static Brazilian test, quasi-static uniaxial compression test, dynamic Brazilian test using Split Hopkinson Pressure Bar (SHPB) apparatus. Through these demonstrations, the applicability of the newly developed 3-D HFDEM code is shown.