Dynamic Failure Behavior of Conglomerate under Impact Loading: Experimental and Numerical Insights for CO<sub>2</sub> Storage Applications.

Abstract

The dynamic failure behavior of conglomerate is governed by multiscale mechanisms and fractal characteristics that are crucial for assessing the integrity of underground CO₂ storage reservoirs. This study presents an integrated experimental-numerical investigation into the strain rate-dependent mechanical response and fractal fragmentation patterns of conglomerate under high strain-rate loading. Dynamic compression tests were performed using a Φ50 mm split Hopkinson pressure bar (SHPB) system over strain rates ranging from approximately 96 s^-1 to 202 s^-1, alongside finite element simulations. The results show a near-linear increase in dynamic compressive strength with increasing strain rate, as the dynamic increase factor (DIF) rises from 1.3 to nearly 2.0. Energy analysis reveals significant increases in incident, reflected, and dissipated energies at higher strain rates, promoting rapid crack initiation and propagation. Fragmentation analysis based on fractal theory indicates that fragment size distributions follow power-law scaling, with the fractal dimension increasing systematically with strain ratesignaling more intense fragmentation. Failure modes transition from dominant axial shear cracking at lower strain rates to combined axial shear and lateral tensile cracking at higher rates, accompanied by greater crack density and finer fragment sizes. Numerical simulations replicate these phenomena and highlight the influence of gravel inclusions in altering local stress fields, leading to crack deflection, branching, or arrestkey indicators of fractal fracture development. These findings elucidate the intrinsic fractal nature of dynamic damage evolution in conglomerate and provide a quantitative framework for multiscale modeling of impact-induced failure. The insights contribute to fractal-based constitutive modeling approaches and support geomechanical risk assessment for geological CO₂ sequestration applications.