Due to poor fragmentation, poor level cut, back-break, and blasthole blowup, inefficient blasting performances brought on by the watery borehole have a detrimental effect on mine output. Additionally, they raise the dangers to the environment and public safety by producing harmful vapours, fly rock, and excessive vibration.
The incomplete explosion of the water-contaminated explosives is the primary source of the majority of the negative impacts of the watery boreholes. To put it another way, if the water is totally separated from the explosive column, which promotes a full explosion, the rate of negative consequences will be reduced (Jang et al., 2018a).
The full explosion would increase the duration of the induced explosion energy actions inside the rock mass, increase the stress oscillation caused by the water in a borehole, and create significant synergies with the favourable rock breaking conditions of the saturated rock mass, all of which would maximise rock breakage performances and minimise the negative effects of a watery borehole.
The majority of adverse effects of the water on blasting performances are due to the deterioration of the explosive. When explosives are immersed 24 hours in water, ANFO will loss 98% of Ammonium nitrate (AN) while the water-in-oil based emulsion explosives loss 0.5% AN (Ni et al., 2012). Although the degree of the water’s negative effects would vary depending on the type of explosive, it is inevitable when the water in the borehole comes into direct contact with explosives.
The length of time an explosive sleeps in a borehole and the borehole’s moisture content determine how much explosive deterioration results from water. The phenomena has the potential to significantly alter the chemical components of nearby explosives. The moistened explosive becomes desensitised and frequently fails to ignite, especially when it comes to hygroscopic explosives like ammonium nitrate fuel oil (ANFO).
Given that the adverse effects, the water in a borehole would result shorten the diameter of the detonable explosive column, decelerate the velocity of detonation (VOD), toxic fume due to the incomplete explosion, and residual explosive in a borehole in a severe condition (Jang et al., 2018b).
In a wet borehole, the VOD would be much slower than in a dry one because of the moist borehole wall and the degraded explosive along the borehole wall.
Reference
Jang, H., Handel, D., Ko, Y., Yang, H.-S., & Miedecke, J. (2018a). Effects of water deck on rock blasting performance. International Journal of Rock Mechanics and Mining Sciences, 112, 77–83. https://doi.org/10.1016/j.ijrmms.2018.09.006
Jang, H., Handel, D., Ko, Y., Yang, H.-S., & Miedecke, J. (2018b). Effects of water deck on rock blasting performance. International Journal of Rock Mechanics and Mining Sciences, 112, 77–83. https://doi.org/10.1016/j.ijrmms.2018.09.006
Ni, O., Zhang, K., Yu, Z., & Tang, S. (2012). Powdery Emulsion Explosive: A New Excellent Industrial Explosive. Journal of Energetic Materials, 30(3), 183–195. https://doi.org/10.1080/07370652.2010.550599
