The Role of Water in the Dynamic Mechanical Behaviors of a Granitic Rock

Abstract

ABSTRACT Rock masses are frequently exposed to dynamic stress perturbations associated with natural events (e.g., earthquakes, landslides, and rock bursts) and engineering operations (e.g., blasting, explosion, and induced earthquakes). Understanding the dynamic mechanical characteristics of rock masses is essential to many geo-engineering applications such as underground excavation and hydrocarbon energy exploitation. Water is ubiquitous in the Earth's crust and plays a vital role in the dynamic mechanical behaviors of rock masses; hoever, the effects of water on the dynamic mechanical characteristics of rocks are still not fully understood. Therefore, it is necessary to carry out more dynamic tests to understand their mechanical responses to the presence of water. To this end, we conduct dynamic uniaxial compressive tests on dry and water-saturated granite rock samples via the split Hopkinson pressure bar (SHPB) technique. The test results demonstrate the strain rate dependence of dynamic mechanical properties of both dry and water-saturated granite rock specimens. The presence of water lowers the dynamic compressive strength and elastic modulus of granite rock specimens. The dynamic increase factor (DIF), characterizing the strain rate sensitivity of dynamic mechanical properties, for wet granite rock specimens is higher than that for dry ones over the tested strain rate range. These findings improve our understanding of the water effects on the dynamic mechanical behaviors of granite rocks. INTRODUCTION Dynamic loading is commonly encountered in natural activities, such as earthquakes and volcanic eruptions, and in engineering operations, such as rock blasting and hydraulic fracturing (Elsworth et al., 2016; Zhang & Zhao, 2014; Bažant & Caner, 2013). Such dynamic disturbance could strongly affect the mechanical behaviors of rock masses, causing the deterioration and damage of rock supports and structures. Understanding the dynamic mechanical behaviors of rocks is therefore essential for the design, construction, and maintenance of tunnels and caverns, defense and military infrastructures, mining facilities, etc. (Li et al., 2017; Qian & Lin, 2016; Zhao et al., 1999). Moreover, dynamic loading at high strain rates could be one of the origins of rock pulverization identified near the active faults, a marker of coseismic damage due to strong earthquakes (Aben et al., 2017; Doan & Gary, 2009). The knowledge concerning rock mechanical responses to dynamic loading could provide insights into rock pulverization, advancing the understanding of earthquake physics and seismic faults (Smith & Griffith, 2022; Griffith et al., 2018; Aben et al., 2016). In this context, more and more attention has been paid to the mechanical behaviors of rocks subjected to dynamic stresses.