Study On Reasonable Millisecond Time And Extra-Depth Of Borehole In Open Pit Blasting

Reasonable extra-depth is the key to not produce toe rock in open pit millisecond deep-blasting. Less extra-depth will have greatly increased the possibility of toe rock while more extra-depth will cause excessive waste of drillings and explosives and destroy the rock surface integrity of the next step which makes difficult to perforation operation. So studying extra-depth is of great significance to improve blasting effect and ensure all work closely. Reasonable millisecond time is the key to blasting technology. The significance of studying reasonable millisecond time is not only help to improve blasting effect and mechanism analysis, but also provide the basis to the development of new types of industrial explosives and blasting equipment. So it is also significant to studying the millisecond time.This paper summarizes the research of extra-depth in open pit deep-hole blasting, describes the main faces of extra-depths and the views of domestic and foreign scholars, and introduces the method of determining the extra-depth values in current home and abroad fields.High-speed video technology analyzed the blasting process in Dumu mining area of Gongchangling Iron Mining. Discussing the law of rock movement and deriving the function of rock displacement and time with rock movement. From the view of formatting the new free surface, it can calculate the millisecond time from the formula. Determining millisecond time by this method is basically coincided to ideal time of actual production. Secondly, we observe and analyze the rock movement velocity of the slope of the stairs with high-speed video. Its regression analysis shows the relationship of wire-bound drug-density、explosives consumption and rock movement velocity of slope. It provides the basis to predict the concentration and the thrown distance of blasting pile.