ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

1aPA5. Underwater explosion shock wave due to a buried charge.

Alan Powell

Dept. of Mech. Eng., Univ. of Houston, TX 77204-4792

The explosive removal of off-shore oil platform structures has an environmental impact on marine life because of the shock waves from the buried charges. For an in-water detonation the similarity parameter (W[sup 1/3]/R) is well known (W= charge weight, R=radius to observation point), with peak pressure p[inf max]= const.x(W[sup 1/3]/R)[sup (alpha)], (alpha)=attenuation coeff.(approximately equal to)1.13 (Arons, 1954). Combining the similarity method with ray theory gives, for a point distance a above the bottom due to a charge buried distance b below it, p[inf max]=const.x(W[sup 1/3]/R)[sup (cursive beta)]{(a+b)/b}[sup (cursive beta)-(alpha)] with (cursive beta)=bottom attenuation coeff. Now p[inf max] is a function only of (W[sup 1/3]/R) only on horizontal planes (a+b)/b= const.; moreover for given R, the pressure increases with height a above the bottom. Full-scale measurements by Connor (1990) confirm these findings, also yielding (cursive beta)(approximately equal to)1.99. The pressure now depends more acutely on charge weight, p[inf max]~W[sup 2/3]; but more weakly on burial depth than p[inf max]~1/b[sup 2.6] as sometimes assumed, e.g., in deep water a&R>>b, p[inf max]~1/b[sup 0.86]. Constant peak pressure contours follow R=const.xcos[sup ((cursive beta)-(alpha))/(alpha)](theta), (theta)=angle to vertical.