Mechanism of dynamic rock fragmentation by electrohydraulic shock waves under multiphysics coupling

In response to the engineering demand for efficient fragmentation of deep hard rock, as well as the critical industrial challenges of low rock-breaking efficiency, high operational cost, and severe wear of drilling tools associated with traditional mechanical drilling, this paper focuses on electrohydraulic shock wave rock fragmentation (also known as electrohydraulic fragmentation) technology. Aiming at the limitation of existing studies that lack a dynamic evolution model integrating liquid electrical breakdown and rock-fragmentation process, a multiphysics numerical model coupling circuit field, current field, acoustic field, solid mechanics field, and dynamic damage field was developed. The model introduces an “electrical damage” variable to describe the evolution process of the liquid-medium breakdown, establishes a rock elastobrittle dynamic damage constitutive model considering strain-rate effects, and quantitatively characterizes rock mesoscopic heterogeneity through a Weibull distribution, enabling a complete reproduction of the nanosecond-scale dynamic process of electrohydraulic shock wave rock fragmentation. Based on the established multiphysics coupled model, this study clarifies the three-stage evolution law of plasma channels and the hysteretic propagation characteristics of induced shock waves, quantifies the regulatory effect of pulse parameters on liquid electrical breakdown delay, and reveals the combined influence mechanisms of rock heterogeneity, pore structure, electrode-to-rock distance, cyclic pulse loading, and in situ geostress on rock-fragmentation performance. The findings elucidate the chain-type fragmentation mechanism of the electrohydraulic shock waves, providing a theoretical foundation for its engineering application in deep energy development.