The Value of Detonating Caps in Blasting

摘要

It is the nature of the initial detonation to the powder around the cap which governs the greater or less effect of the explosion of the whole charge.The cap communicates to the first particles of powder a disruptive impulse,which,according to the nature and strength of the cap,more or less completely overthrows their equilibrium and decomposes the powder with great energy,setting up sympathetic vibrations that explode the particles of powder in turn by the violent disturbances or friction between them in a regular succession of impulses and decompositions,which,if started with sufficient energy,are of such intense heat and velocity that the rupturing force of the explosive is developed practically instantaneously.This detonation has already been shown to be not only the result of mechanical force,but a combination of extremely sudden chemical and dynamical reactions which set up vibrations to which different powders are more or less susceptible,and these explosive reactions will be propagated through the mass of the powder according to the intensity of the vibrations and the resistance with which their motion is opposed by the nature and consistency of the powder,whether it be difficult or easy to oxidize,soft and plastic like dynamite,or hard.If the initial detonation of the powder surrounding the cap is of the highest degree,the vibrations will be most intense and will be propagated further through the mass than by a poorer detonation.Hence the different degrees of detonation.Unless the first particles of powder are so thoroughly decomposed by a detonation of high order,or first degree,as to convey the necessary heat and energy to detonate the whole charge,the greatest force of the powder will not be developed.There will frequently be unbottomed holes or pieces of unexploded powder scattered about,or both,and the air in the mine will be contaminated with some obnoxious gases that have not been completely oxidized.