Experimental and numerical study of underwater explosion load distribution on steel plate

This study investigates the distribution characteristics of underwater explosion loads on steel plate structures through combined experimental and numerical approaches. Underwater explosion experiments with TNT charges of 25 g, 50 g, and 75 g were conducted to obtain time histories of incident and reflected pressures. The reflected-to-incident pressure ratio at the plate center ranged from 1.44 to 1.65, and the measured peak pressures and first pulse periods agreed well with the unified bubble theory, with maximum deviations of 9.01% and 4.62%, respectively. A three-dimensional finite element model was developed using LS-DYNA and validated against the experimental data. Based on the validated model, the propagation of shock waves and the evolution of bubbles were analyzed. Cavitation is recognized as a potentially important mechanism but is not explicitly resolved in the present model, which focuses on the initial shock-wave and early bubble-pulse stages. Two dimensionless parameters were introduced, the shock factor SF for shock wave intensity, and the stand-off parameter γ for bubble-wall interaction. The results show that the reflected pressure on the plate surface exhibits a non-uniform distribution, decreasing from the center to the edges and reaching minimum at the corners, with edge-to-center pressure ratios of 0.39–0.63 for the shock wave stage. For the bubble pulse stage, this ratio drops from 0.33 to 0.61 at γ = 2.27–0.17–0.48 at γ = 1.56, indicating that as the bubble approaches the wall ( γ < 2), the collapse becomes increasingly asymmetric and the pressure distribution becomes more irregular. These quantitative findings provide practical references for engineering design to mitigate underwater explosion risks.