Morphological evolution indicates the transformation of stress interference in parallel fractures.

Fracture propagation is ubiquitous in natural strata and geological engineering, influencing key processes such as engineering stability assessment and design optimization. While prior studies have investigated the propagation of individual fractures through gelatin experiments, stress interference between fractures has been less considered. This study presents an innovative mirror-symmetric dual-fracture experiment that dynamically correlates fracture morphology with stress interference. Using light attenuation, we quantified the morphological evolution and identified distinct propagation regions governed by different degrees of stress interference. The results indicate that a regional transition occurs when the fracture radius approaches the fracture spacing. We defined a stress interference factor (β) to quantitatively characterize the interaction and derived an analytical model for β, which shows satisfactory agreement with experimental data. Through energy balance analysis during stagnation events, we revealed that the partitioning between elastic energy storage and viscous dissipation varies with fracture radius, explaining the observed differences in stagnation frequency and duration at different propagation stages.