Experimental study on dynamic fracture and fragmentation behavior of surrounding rock in salt cavern gas storage under impact loading

Abstract

Salt rock is a critical medium for underground energy storage (e.g., oil, natural gas, and CO₂). However, it faces significant challenges under dynamic loading conditions, such as blasting and seismic events, threatening the stability and safety of salt caverns. The dynamic fracture behavior and failure mechanisms of salt rock under high-strain-rate loading remain inadequately understood, particularly concerning fracture propagation patterns and energy dissipation characteristics. This study investigates salt rock, employing a Split Hopkinson Pressure Bar (SHPB) dynamic impact test system integrated with high-speed photography and digital image correlation (DIC) techniques. The mechanical properties and fracture propagation behavior of salt rock under impact loading are systematically analyzed. Based on fractal dimension theory, particle size distribution analysis of fractured salt rock is conducted, and scanning electron microscopy (SEM) is employed to examine the crushed fragments. The results show that: (1) Salt rock material is a strain-rate-sensitive material, the dynamic peak strength of salt rock is positively correlated with strain rate under impact loading, and the fragmentation pattern shifts from coarse particles to finer grains as the strain rate escalates. (2) Salt rock exhibits distinct fracture propagation stages under dynamic loading, with an increasing fragment fractal dimension with strain rate. (3) Within the strain rate range of 68.39 s⁻¹–83.51 s⁻¹, the dynamic compressive strength of salt rock is lower than the static compressive strength. (4) As the impact pressure increases beyond the threshold of 0.3 MPa, the failure characteristics of salt rock exhibit pronounced “avalanche” dynamic behavior. These findings are highly significant for assessing geological engineering disaster risks under extreme loading conditions.