A Study on the Empirical Relation of Rock Mass with Respect to the Dynamic Response of Intact and Precracked Rock Specimens

The characterization of rock masses is a fundamental aspect of geotechnical engineering, influencing the design and safety of various underground mining and subsurface structures. This study explores an innovative approach to empirically develop a relation between the rock mass behavior of the rocks based on the dynamic responses of intact and precracked rock specimens under varying loading conditions using a universal testing machine (UTM) and a split Hopkinson pressure bar (SHPB) device. The present study uses three rock types, i.e., basalt (igneous), sandstone (sedimentary) and quartzite (metamorphic). A three-dimensional (3D) finite-element (FE) numerical model is developed to validate the experimental results using a strain rate–dependent modified Drucker-Prager constitutive model. The simulated parameters are then used to capture the stress–strain behavior of preflawed rock specimens at different crack orientations of 0°, 30°, 45°, 60°, 75°, and 90°. The data obtained from experimental results of intact rock specimens and simulated results of precracked rock specimens are used to obtain the strain rate–dependent rock mass properties of the three rocks using empirical relations. Finally, an equation is proposed relating the global tensile strength of the rock mass, the tensile strength of the intact rock specimen, and the stress generated at the tip and center of the precrack in an intact rock. A factor A is proposed in the present study that is sensitive to rock types, strain rates, and angle of crack orientations.