Special aspects of explosive loosening with minimal rock displacement

Evgeny Shevkun,Aleksander Leshchinsky,Andrey Plotnikov,I Rasskazov,S Tkach

doi:10.1051/e3sconf/202019201003

Abstract

The dynamics of the development of an industrial mass explosion at deceleration intervals of 150x200 ms on a frame-by-frame video recording on a consumer video camera with a shooting frequency of 25 frames per second is studied. Possibilities of visual assessment of the explosion site of individual borehole charges are evaluated. The main difficulties in recording processing are caused by the difference in the intervals between frames (40 ms) and decelerations between charges (50 ms). A significant deviation of the actual deceleration intervals from the nominal value was revealed, which significantly changes the actual picture of the development of a mass explosion, including an increase in the actual development time of a mass explosion against the calculated one. The passage through the zones of the location of individual borehole charges up to 40 stress waves was established. Such multiple impacts of stress waves are expressed in a decrease in the magnitude of the interval velocities of dust and gas emissions as the number of impacts of stress waves increases. Due to the multiple effects of stress waves in the extension stage, the fracturing of the rock mass increases. This is expressed in a decrease in the dynamics, and then in the termination of the outburst of bottom hole material as the disturbance of rocks in the prefracture zone increases. There is no breakdown of rocks; the “ore-rock” contacts have retained their original position, which makes it possible to reduce the dilution of ore to a minimum.

Highlights

Explosive loosening of rocks is the main process of open pit mining, which determines the main qualitative and quantitative indicators of subsequent technological processes, primarily the excavation of ore areas with minimal dilution.It is explosive loosening that determines the amount of dilution in the process of formation of the disintegration of the rock mass
Using the graphoanalytical method [1], a sequence of blasting borehole charges was constructed according to the above diagram of the block's blasting network, and the number of stress waves passing through the area of each blast hole during the development of a massive explosion was revealed, taking into account the size of the destruction and pre-destruction zones
Development of a mass explosion, of interest is the part of the block located in front of the cut row, since the influence of neighboring charges through the destruction zone affects only the second row along the cut - the third row does not affect the number of passing stress waves even in the cut row (Fig. 2), and emissions from wells behind the cut row cannot be identified

Summary

Introduction

Explosive loosening of rocks is the main process of open pit mining, which determines the main qualitative and quantitative indicators of subsequent technological processes, primarily the excavation of ore areas with minimal dilution (mixing of waste rocks). It is explosive loosening that determines the amount of dilution in the process of formation of the disintegration of the rock mass. The ideal option is to loosen the rocks with minimal displacement, which allows us to maintain the primary position of the "ore-rock" contacts, refined in the process of drilling production of blocks with blast holes

Target setting

Experimental research

Results discussion

Conclusions