Determination of High-Strain-Rate Stress–Strain Response of Granite for Blast Analysis of Tunnels

Abstract

The present work aims to understand the stress–strain response of an igneous rock, granite, under high loading rate through detailed experimental and numerical analyses. The high-strain-rate characterization of granite rock was performed for two different diameters and five different slenderness ratios of the rock specimens using a 76-mm-diameter split Hopkinson pressure bar (SHPB) device in an effort to determine the appropriate specimen dimension for granite to be used in an SHPB test. The stress–strain response of the rock specimens was studied by systematically varying the length of the striker bars and the gas gun pressure values of the SHPB device. The petrological and static characterization of the granite rock was also carried out to assess the response of the rock specimens. Finally, a methodology was proposed to characterize granite rock specimens under high loading rate. Further, a numerical simulation of the SHPB test on granite rock was performed using the strain rate–dependent Johnson-Holmquist 2 (JH-2) model available in the finite-element software LS-DYNA. The simulation results were compared with the experimental data; thus, the parameters of the JH-2 model for granite rock were determined. The determined parameters were then used in blast analysis of a tunnel subjected to 20-kg TNT explosive.