The Summary Of Open Pit Deep Hole Bench Blasting About Hole By Hole Initiation Of Delay Time Selection

The article introduce the influence factors of reasonable delay time selection of open millisecond blasting.In this article,it based on the analysis about the optimal delay time selection at home and abroad,summarizes several mainly exist of major theoretical hypothesis and calculation of relevant theory and semi empirical mathematical model.There was presented on the different influencing factors of different hypotheses focus and the mechanism of the affecting factors,and analyzes several hypotheses test conditions and the advantages and disadvantages.For future improvement in China's open pit blasting effect,and give guidance theory of the improvement of the economic benefit In the end,according to the specific engineering examples,this article points out the future direction of millisecond blasting for open selection of optimal delay time.In order to study the optimal delay time of inter blasthole of millisecond blasting,which is calculated through shock wave and explosive gas energy,an detonation gas motion equation and an dynamic equation are proposed,which is consisted of detonation gas destruction scope,time,and the mathematical model of velocity.Specifically,many theories,such as rock broken theory,wave theory,theory of fracture mechanics,thermodynamics theory and theory of fracture mechanics are utilized during formula derivation.Moreover,after correcting the semi-empirical formula from previous study,a theoretical model of millisecond blasting's delay time is established.As a result,the calculated optimal delay time is 46ms after inserting the rock mechanical properties.By contrast,the experiment,explosions of delayed-detonation combination in different period,reveals that the optimal delay time is 50ms,which.is consistent with theoretical result.In order to improve the blasting vibration and boost the efficiency of blasting energy,this paper is mainly focus on the delay time control research through transmission law.Making an experiment with a delayed-detonation scheme in different period,which selecting common detonator and Orica high precision detonator,measure vibration of the earthquake wave when testing,based on seismic wave function optimization theory foundation,then research the measured data and wavy figure,and then we can find out the variation characteristics of the rules of earthquake wave propagation,peak velocity,domain frequency,band energy and the total energy in different delayed period.At the same time,according to the characteristics to find velocity map which Synthesized by triaxial vibration wave and displacement map which assembled by speed Calculus correspond to the maximum in same time.On the basis of peak velocity-vibration displacement distribution characteristics,fitting method for Gaussian multi-peak is applied for measured vibration wave,to give the band energy maximize time points about t = 60ms,blasting vibration around the minimum time for t = 25ms.In order to study the impact of different delay time on vibration of bench blasting,the dynamic finite element software LS-DYNA was applied in numerical simulation.The four ways of initiating,whose delay time are 0ms?17ms?25ms?42ms respectively,were adopted in two blast holes model.During the simulating process,three monitoring points were selected on the bottom stage,from where four kinds of synthetic velocity-time curves are formed.These curves show that peaking velocity is bottom at 25ms with a minimum vibration,while the stress concentration emerges at slope.