Study on stress transfer mechanism and energy decay model of underwater supercritical CO 2 phase-change shock waves at solid–liquid interfaces

The deep-water channel improvement project on the Yangtze River requires low-vibration, zero-pollution rock-breaking technology. SC-CO2 phase-change fracturing has garnered significant attention due to its physical expansion and pollution-free nature. However, the energy dissipation mechanism of shock waves traversing the rock–water interface remains poorly understood. To address this, field tests of SC-CO2 underwater phase-change fracturing were conducted. A full-process dynamic simulation model based on the Lagrange-FSI algorithm in LS-DYNA was established. This study systematically reveals for the first time the ‘stress-energy’ coupling attenuation law of SC-CO2 underwater phase-change shock waves at the rock–water interface, quantifying stress transmission and energy dissipation rates within rock–water media while elucidating the stress-energy transfer mechanism at the solid–liquid interface. Results indicate that only 7.7% of the total phase-change energy (231 kJ across 20 tests) transmitted into water as elastic waves, with 92.3% dissipated within the fragmentation zone, fracture zone and residual dissipation. An energy attenuation model was established using water depth H and resistance line L as dual variables, enabling quantitative prediction of underwater fracturing energy transfer. This model provides a preliminary tool for rapid energy–damage assessment of submerged reefs, though its general applicability requires further validation under more field conditions. The research findings provide theoretical support for optimising SC-CO2 underwater reef fracturing parameters and controlling ecological impacts.