Research Projects

Geological formations, comprising both hard and soft rock masses, have consistently posed significant challenges in the construction of tunnels and underground infrastructure. These subterranean and mountainous structures are subjected not only to static overburden stresses from the weight of overlying soil and rock but also to dynamic loads from extreme events such as earthquakes and explosions. These events are highly transient in nature and induce elevated strain rates in the rock mass. Strain rates resulting from seismic activity can range from 1/s to 100/s (Asprone et al., 2012; Li and Li, 2012; Xu et al., 2018), while explosive events may generate rates between 102/s and 104/s (Ngo et al., 2007; Chakraborty et al., 2014; Børvik et al., 2015). Such high strain rates significantly influence both the stiffness and strength of rocks. It is well-established that rocks are inherently heterogeneous, often containing numerous microcracks, joints, and fissures developed during geological processes. These inherent defects can evolve into critical failure planes under dynamic events such as blasts, missile impacts, or earthquakes. Conversely, such microcracks may aid in controlled fragmentation during mining operations. Therefore, a thorough understanding of crack initiation and propagation in rock masses under dynamic loading is essential, particularly in predicting progressive failure. For the resilient and safe design of infrastructure embedded in rock, it is vital to characterize the host rock not only under static conditions but also under high strain rate loading scenarios. Numerous researchers have investigated rock behavior at high strain rates using a variety of experimental setups, such as triaxial compression tests, drop-weight apparatus, split Hopkinson pressure bar (SHPB) systems, and plate impact devices (Langseth and Larsen, 1994; Field et al., 2004; Shukla et al., 2003; Shukla et al., 2010; Zhang and Zhao, 2014; Singh et al., 2015). These studies have explored rock properties including microstructure, porosity, anisotropy, and strain energy absorption. In addition, they have assessed the influence of dynamic loading parameters, loading mechanisms, failure modes, and fracture mechanisms.An increase in rock strength under dynamic conditions is often attributed to wave propagation effects. Mishra (2019) examined the influence of striker bar length and amplitude in SHPB tests, highlighting how wave characteristics impact rock response. Extensive investigations have been carried out by Mishra (2019) on brittle materials such as rock and concrete, evaluating their behavior under dynamic compressive, tensile, and shear loads using SHPB setups. These studies incorporated advanced diagnostics, including digital image correlation (DIC), computed tomography (CT) scans, and acoustic emission (AE) monitoring. Furthermore, Mishra et al. (2025) conducted detailed analyses to identify fracture propagation patterns in tested rock specimens. Although certain aspects of crystal-scale behavior remain understudied, the present research proposal aims to bridge this gap by developing a micromechanical model. This model will integrate three-dimensional flaw distributions, fracture mechanics, crystal plasticity, and material plasticity into a unified constitutive framework implemented through UMAT in a dynamic explicit solver. The proposed study also intends to synthesize data obtained from high-speed imaging, CT scans, and AE measurements to replicate and eventually replace experimental investigations of rock behavior under dynamic loading. The anticipated results will be instrumental in accurately predicting damage to subsurface infrastructure subjected to extreme external loads.