Depth Dependence of Bubble Pulse Periods of Point and End-Fired Line Charges

Abstract

A theory of the depth dependence of the first bubble pulse period of an infinitely long cylindrical charge is developed. The charge is represented by a cylinder of adiabatic gas and the time equation for expansion from its initial radius to equilibrium is derived as a function of the weight of explosive per unit length and the hydrostatic head. Theoretical results are compared with measured bubble pulse periods of end-fired line charges detonated at depths between 90 and 10 600 ft. The length-to-diameter ratio of the charges varied from 45 to 320 and the weight of explosive per unit length varied from 0.11 to 0.43 lb/ft. There is substantial agreement between theory and experiment, the agreement improving as the length-to-diameter ratio of the charge increases.