Energy distribution of underwater explosion near the water-soil interface in centrifuge modelling

Comprehensive methods have been established for analyzing the shock wave energy and bubble pulsation energy of underwater explosions in the free-field. However, the research on the energy distribution of underwater explosion near the water-soil interface remains lacking. To investigate the energy coupling characteristics of the underwater explosion near the water-soil interface, a series of underwater explosion centrifuge model tests were designed and conducted with various explosive heights above the water-soil surface. Images of the bubble pulsation process, water pressure and pore-water pressure in the soil were recorded. By analyzing the bubble pulsation period, water pressure and pore-water pressure response, a calculation method for determining the explosion energy in water near the water-soil interface was proposed theoretically. It is indicated that as the scaled height increases, both the shock wave energy and bubble pulsation energy in water rise. Furthermore, the equivalent coefficient of impulse for underwater explosion near the water-soil interface is developed to analyze the ground shock energy characteristics induced by underwater explosion near the water-soil interface. As the scaled height increases, compared to the bottom-charge underwater explosion, the equivalent coefficients of impulse exhibits different variation across different phases. Finally, empirical formulas for calculating the equivalent coefficient of impulse under different scaled heights are derived. The research findings can provide a theoretical basis for the damage assessment and protective design of underwater structures such as subsea tunnels and submarine oil or gas pipelines.