Effect of delay intervals on fragment dispersion

Blasting of a row of boreholes provides multiple effect of stress waves on rock mass and contributes to the increased concentration of micro-fractures in the zone of pre-destruction. Extension of delay intervals provides time allowance for fractures to grow as long as possible and to merge. The first explosion produces great emission of dust, gas and broken rocks. Then, the explosion products enter the created fractures and wedge them, which leads to reduced emission from the borehole and to the size reduction in broken rocks. Blast energy is mostly spent to fragmentation and, less, to ejection of broken rocks, which should be taken into account in design of gas-permeable shelters for explosion sites. The earlier developed technology of nodispersion loosening blasting of solid rocks under gas-permeable elastic shelters showed high reliability and economic efficiency as compared with the other methods of sheltering sites of explosion. However, this technology neglects influence of delay intervals on the explosion dynamics. With the view of studying reduction in gas and dust emission from blastholes and mitigation of impact exerted on the elastic shelter (auto tyres), three large-scale experimental blasts were carried out at delay intervals from 150 to 1000 ms. In each experimental block, 20 boreholes were drilled in a single row. The upper limit for delay intervals to have influence on the blast impact was determined from tests. At the delay intervals of 1000 ms (even without stemming), no dispersion of fragments beyond the block outline was observed. The influence of the delay intervals on quality of rock fragmentation by blasting and on the seismic load was beyond the scope of this study.

Keywords: fragmentation by blasting, delay interval, pre-fracture, single-row delayed blasting, microfracture, explosion products, impact, large-scale blast.
For citation:

Kostiunina О. А., Shevkun Е. B., Leshhinskij А. V. Effect of delay intervals on fragment dispersion. MIAB. Mining Inf. Anal. Bull. 2021;(12—1):107—120. [In Russ]. DOI: 10.2501 8/0236_1493_2021_121_0_107.

Acknowledgements:
Issue number: 12
Year: 2021
Page number: 107-120
ISBN: 0236-1493
UDK: 622.235
DOI: 10.25018/0236_1493_2021_121_0_107
Article receipt date: 18.07.2021
Date of review receipt: 19.10.2021
Date of the editorial board′s decision on the article′s publishing: 10.11.2021
About authors:

Kostiunina O. A.1, postgraduate, Pacific National University, 006934@pnu.edu.ru;
Shevkun E. B.1, Dr. Sci. (Eng.), professor, professor;
Leshhinskij A. V.1, Dr. Sci. (Eng.), associate professor, professor;
1 Pacific National University, 680035, Tikhookeanskaya, 136, Khabarovsk, Russia.

 

For contacts:

Kostiunina O. A., e-mail: 006934@pnu.edu.ru.

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