<p>Construction-induced disturbances in rock engineering are rate dependent and may promote progressive failure in fractured rock. Although crack interaction strongly affects the macroscopic failure mode, its loading-rate dependence at the crack-tip scale remains insufficiently quantified. Brazilian disc specimens containing two parallel pre-existing flaws were simulated with the Particle Flow Code at loading rates of 0.005–0.5 m/s. Mixed-mode stress intensity factors and T-stress were extracted from near-tip displacement fields through Williams-series inversion with rigid-body-motion correction. Crack-initiation angles were predicted with the maximum tangential stress criterion, and damage evolution was characterized through moment-tensor-based acoustic emission analysis. The predicted initiation angles agreed with the simulated cracking patterns, while the extracted crack-tip parameters remained stable before initiation. Before crack initiation, crack-tip driving parameters were governed mainly by flaw geometry. After initiation, the interaction became more sensitive to loading rate. At low loading rates, the first-initiated crack had sufficient time to release and redistribute local stress, which shielded adjacent tips and promoted localized tensile-dominated failure. At high loading rates, shorter initiation intervals limited stress redistribution, weakened shielding, and produced rapid multi-tip activation, distributed energy release, and greater shear involvement. These findings indicate that competition between the external loading timescale and the post-initiation stress-redistribution timescale governs rate-dependent crack interaction in double-flawed rock.</p>