Pre-split Blasting in Lead Zinc Mine to Maintain Stable Slopes
Rampura Agucha mine is the Indias largest Lead-Zinc open-pit mine of M/s Hindustan Zinc Limited. The mine had the initial reserves of 63.648 million tonnes of Pb-Zn composite sulphide ore containing 13.54% of Zn and 1.97% of Pb. The ore body is hosted by graphite mica sillimanite gneiss in lens shaped doubly plunging synform. The average width of ore body is 58 m over a strike length of 1550 m. The present depth of the pit is 180 m and the ultimate pit will be 372 m. Presplit blasting was implemented in all the benches in an attempt to make them safer and more competent. Pre-split blasts were carried out at all the benches in foot wall (FW) side in existing cut back. The pre-splitting was envisaged for achieving steeper slope angle. One of the objectives in pre-split blasting was to control over break so that the final pit wall slope and benches of the final planned excavation limit is stable. The other objectives of the implementation of pre-splitting was to maintain highwall stability for access roads, ramps, entry points etc., which must remain for extended periods during the mine life. This also reduces clean up times and wears & tears on haulage equipment as a result of reduced material falling-off of the high-wall and onto the haulage road. Initially the available drill machine was of 115 mm diameter and was not able to drill inclined holes.Mine management does not wish to acquire new equipment at that stage. A master plan of the vertical pre-split holes position at spacing of 1.2 m was prepared. The pre-split line was designed at 1 m away from the final crest line from the berm to be left. The available explosive was in the cartridge diameter of 25 mm which provided decoupling by factor of 4.56. Regarding the blast condition and type of explosive, energy reduction in holes in pre-split row was achieved by tagging of cartridges of slurry explosives to the detonating cords at defined intervals. In the experimental trials the mouths of the pre-split holes were left without explosives from 0.8 to 2.7 m. In the latter stage the inclined holes of 80°, 70° and 60° with 115 mm diameter were experimented. The best result were encountered with 60° inclination and the mouth of the pre-split holes were uncharged by 2.2～2.7 m. The charge factor of 0.44 to 0.90 kg/m2 was experimented depending upon the rock types.
pre-split blasting wall control back breaks pit slope angle pit wall stability
P.K.Singh M.P.Roy
Blasting Research Group, Central Institute of Mining & Fuel Research, Dhanbad 826 015, India
国际会议
The Second Asian-Pacific Symposium on Blasting Techniques(第二届亚太地区爆破技术研讨会)
大连
英文
231-238
2009-07-01（万方平台首次上网日期，不代表论文的发表时间）