Long-period delay loosening blasting in open pit mines

The article discusses enhancement of loosening blasting with longer periods of delay between blasts in hard rocks. In recent decades scientists and practitioners in blasting have agreed on two-stage mechanism of rock fracture under blast load. At the first stage of volumetric pre-fracture, stress waves from blasts subject rocks to compression and tension, and microand macro-cracks and other defects appear, accumulate and concentrate in rocks. At the second stage of post-fracture, cracks coalesce into larger fractures of dominant destructive nature, the local growth of some cracks results in jointing. The mechanical action of blasting consists both in near-field shattering and in far-field weakening of rocks. Rocks in the far field alter their strength and fracture characteristics and drop into a new pre-fractured state. It is found that cracks grow in length by 10 mm in one compression–tension cycle, which is phenomenologically interpreted as pre-fracture of rocks. Longer periods of delay between blasts enable more frequent effect of the compression–tension cycles, with accumulation of cracks, which is favorable for coalescence of cracks and gradually reduces the size of blocks.

Keywords: blasting fragmentation, delay period, pre-fracture of rocks, weakening of rocks.
For citation:

Shevkun E. B., Leshchinskiy A. V., Lysak Yu.A., Plotnikov A. Yu. Long-period delay loosening blasting in open pit mines. MIAB. Mining Inf. Anal. Bull. 2020;(10):29-41. [In Russ]. DOI: 10.25018/0236-1493-2020-10-0-29-41.

Issue number: 10
Year: 2020
Page number: 29-41
ISBN: 0236-1493
UDK: 622.235
DOI: 10.25018/0236-1493-2020-10-0-29-41
Article receipt date: 29.01.2020
Date of review receipt: 30.04.2020
Date of the editorial board′s decision on the article′s publishing: 20.09.2020
About authors:

E.B. Shevkun1, Dr. Sci. (Eng.), Professor,
A.V. Leshchinskiy1, Dr. Sci. (Eng.), Assistant Professor, Professor, e-mail: 000399@pnu.edu.ru,
Yu.A. Lysak2, General Director,
A.Yu. Plotnikov2, Deputy Chief Engineer,
1 Pacific National University, 680035, Khabarovsk, Russia,
2 AVT-Amur LLC, Blagoveshchensk, Russia.

For contacts:

A.V. Leshchinskiy, e-mail: 000399@pnu.edu.ru.


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