Physio-Mechanical Characterization of Limestone and Dolomite for Its Application in Blast Analysis of Tunnels

Abstract

In the present work, the rate-dependent stress-strain responses of limestone and dolomite, sedimentary rocks, are determined by using a split Hopkinson pressure bar device under a high loading rate. The petrographical, physical, and mechanical responses of the rocks are studied through detailed experimental and numerical analyses. For experimental analyses under a high loading rate, the intact rock specimens are prepared in five different specimen sizes to understand the effect of specimen size on the stress-strain and peak stress responses. It is seen that specimen dimension does not have a significant impact on the dynamic stress-strain response of both rocks; however, the dynamic-to-static peak stress ratio (DIF) varies between 1.8 to 8.1 at any specimen size. Because split-Hopkinson pressure bar (SHPB) specimen dimensions are small compared to any field rock mechanics problem, the rate-dependent rock mass properties are also determined for each rock using Hoek Brown criteria. The calibration of a Johnson-Holmquist (JH-2) constitutive model is done by simulating the SHPB tests on both rocks, and model parameters are determined. Blast analysis in tunnels in the two rocks is performed using the coupled Eulerian Lagrangian (CEL) tool in ABAQUS 2017, the Jones-Wilkins-Lee (JWL) equation of a state for 50 kg trinitrotoluene (TNT) explosives, and JH-2 model parameters for rocks. Stresses and displacements are reported.