Mitigation of propylene oxide/air vapor cloud explosion shockwave hazards using protective forest belts: Experimental and numerical insights

A propylene oxide (PO) release may lead to a vapor cloud explosion (VCE), and the resulting shockwave can still cause significant damage in the far field. Motivated by the need to control shockwave consequences for sensitive receptors such as residential areas surrounding chemical parks, this study examines the mitigation effects of protective forest belts located around the park perimeter under an already occurred VCE scenario, and provides a quantitative evaluation based on combined experiments and numerical simulations. A PO/air VCE test was conducted, and a scaled hedgerow blast experiment was employed as a surrogate validation to examine the reasonableness of vegetation-obstacle-induced shockwave attenuation trends. On this basis, an Euler-Lagrange numerical framework was established and validated against measured peak overpressures, with an average relative error of less than 10 %. Using the validated simulations, we systematically evaluated the influence of canopy coverage and tree height on hazard extents: when coverage increased from 0 % to 65 %, the equivalent safe distance decreased from 62.2 m to 54.32 m, and the fatal and severe injury areas were reduced by 55.92 % and 56.97 %, respectively; when tree height increased from 5 m to 35 m, the safe distance decreased from 61.04 m to 58.13 m, and the total hazardous area decreased by 20.54 %. To support rapid engineering assessment, semi-empirical prediction models were further developed for the total hazardous area and three injury-level zones, and the total-area model achieved an R² of 0.992 within the parameter ranges considered in this study. These results indicate that protective forest belts around chemical parks can effectively mitigate far-field shockwave consequences following a VCE, providing quantitative support for safety-distance evaluation and green buffer design.