The Propagation of Waves near Explosion and Fracture of Rock (1)

Abstract

The basic character of fracture and plastic deformation processes that will be operative under extremely high, yet very transitory pressure, imposed on rock by explosion is studied experimentally. The mode of propagation of transient disturbance is measured by seismometric pick up and strain gage especially devised for this purpose put within the fracture zone and neighboring plastic zone which would be formed by explosion. Magnetic tape recoding system is used partially and play back records are obtained with several ranges of filtering. The strain wave shapes, that is the rise time, the pulse width. etc., are shown to be influenced by applied pressure, the distance from the shot point and free surface; moreover, these pulses are composed by component waves different in propagating velocity. The experimental results are discussed referring to the stress strain relation of each rock determined statically by experiment. In the very neighbourhood of shot point two different kinds of waves are detected. One is the elastic wave of relatively higher frequency, and the other the plastic wave of lower frequency, with the increase of amount of explosive the propagating velocity of the plastic wave is effected and becomes slower.