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Highwall mining hazards and mitigation
Published in John Loui Porathur, Pijush Pal Roy, Baotang Shen, Shivakumar Karekal, Highwall Mining, 2017
John Loui Porathur, Pijush Pal Roy, Baotang Shen, Shivakumar Karekal
Any blasting activity close to highwall mining may affect the stability of highwall mining entries and web pillars, as well as the highwall of an opencast mine from where the workings are to be executed. Ground vibrations generated from day-to-day blasting operations near the highwall mining entries can impose immature roof and side collapse, thereby trapping the continuous miner. Flyrock generated from blasting near the highwall mining can also damage the equipment used for the mining, such as launch vehicles etc., and impose safety concerns for the workers (Porathur et al., 2013). Statutory authorities in India, namely the Directorate General of Mines Safety (DGMS), have stipulated the threshold values of vibrations from blasting for the safety of roofs and pillars in underground coal mines (DGMS Technical Circular No. 06, 2007).
Blasting
Published in Duncan C. Wyllie, Rock Slope Engineering, 2017
Flyrock is the uncontrolled ejection of rock fragments from the blast, which can be a very hazardous condition because of its unpredictability. Common causes of flyrock generation are shown in Figure 13.24. For example, when the front row burden is inadequate or when the stemming column is too short to contain the explosive gases, a crater is formed and rock ejected from the crater. This figure also shows that flyrock can be caused by poor drill hole alignment, and by geologic conditions that allow venting of the explosive gases along the discontinuities in the rock mass.
Optimization of postblast ore boundary determination using a novel sine cosine algorithm-based random forest technique and Monte Carlo simulation
Published in Engineering Optimization, 2021
Zhi Yu, Xiuzhi Shi, Xianyang Qiu, Jian Zhou, Xin Chen, Yonggang Gou
The drilling–blasting method is widely used for breaking rock masses in mines (Wang et al.2018; Singh and Singh 2005). However, only 20–30% of the blast energy is utilized for rock fragmentation, and the remaining 70–80% of the energy is wasted by creating blast-induced ground vibration, backbreak, movement of fractured rock, etc. (Khandelwal and Monjezi 2013). Among these effects, the movement of fractured rock can be analysed at three scales: large scale, medium scale and small scale. At the large scale, the flyrock phenomenon is caused by the blasting operation. The medium scale of fractured rock movement means the overall movement of the blasted muckpile, and the small scale is the rock movement in the blasted muckpile. For the convenience of research, rock movement in the blasted muckpile can be defined as blast-induced rock movement (BIRM). During the blasting process, the ore and waste move towards the free face under the explosive energy, leading to great differences in the preblast ore boundary and postblast boundary, which often cause serious ore loss and dilution during shovel loading. As suggested in previous literature (Gilbride et al.1995; Taylor and Firth 2003), metal recovery can be increased by approximately 25% if the postblast ore boundary is obtained by calculating the BIRM distance. Therefore, research on postblast ore boundary determination considering the BIRM effect is quite important and meaningful for the reduction of ore loss and dilution in opencast bench blasting.