Dynamic behaviour of un-grouted and grouted jointed samples of a brittle rock in Split Hopkinson Pressure Bar tests: Insights from experiments and DEM modelling

Bonded Block Model (BBM) is gaining popularity in understanding the grain-scale micromechanics along with the macroscopic response of rocks to a variety of loading. However, the understanding of the application of BBM and the effect of different parameters on the estimated dynamic behaviour of rocks is lacking. This study aims to investigate the effect of different sample, experimental and modelling parameters on the dynamic response of Kishangarh marble represented via BBM in UDEC. The Voronoi tessellation is used to create the polygonal/polyhedral grain structures along the samples. The modelling micro-parameters of the numerical model are initially calibrated using the experimental observations on intact samples for Split Hopkinson Pressure Bar (SHPB) tests. The numerical model and calibrated parameters were then fully validated with experimental results of jointed and grouted samples. The effect of different flaws (orientations, shape and persistence), experimental (strain rate), grain (heterogeneity and lamina orientation) and modelling (micro-parameters and modelling type) parameters are investigated. The orientation (anisotropy), shape and arrangement (persistence) of flaw affect the dynamic response of jointed samples significantly. The effect was suppressed in grouted samples due to possible strengthening of flaw tips, impeding stress concentration and fracture propagation. The effect of lamina orientation and strain rate was more dominant in grouted samples due to the transition in the behaviour of grouted samples towards intact rocks. The effect of grain/contact heterogeneity was observed to be negligible on micro/macro level responses of samples. The initiation, progression and coalescence of different types of micro-level cracks and failure mechanisms were explored and explained with the BBM model of the rock specimens.