Field investigations into blast design parameters of highly jointed rockmass of overburden: A case study of large opencast coal mine (India)
- Visvesvaraya Regional Coll. of Engineering, Nagpur (India). Dept. of Mining Engineering
- Regional Engineering Coll., Surathakal (India)
- Banaras Hindu Univ., Varanasi (India)
A coal mine with annual production of 2.11 million tons coal with excavation of 6 million tonnes of overburden was worked in three sections with seven benches. Removal of overburden was done by shovel-dumper combination. Overburden rocks consists of medium grained porous Sandstone of average 50 MPa compressive strength and was typified with horizontal open joints. These joints cause venting of gas energy leading to boulder formation of the size ranging from 1 m{sup 3} to 50 m{sup 3}. It was difficult to load these boulders by excavator with 4.6 m{sup 3} bucket capacity. Boulders cause many problems like frequent breakdown of shovels, early replacement of teeth and environmental problems arise due to secondary blasting. Ten trial blasts were conducted in the field and blasting results were analyzed by pre-blast and post-blast surveying. It observed that the main cause of boulder formation was due to misappropriate blast design in jointed rockmass. With the help of trial blasts, blast design parameters were selected and results were analyzed. It was concluded that spacing and burden should be chosen after studying joint pattern at each face and this particular strata spacing burden ratio 1.25 gave optimum fragmentation. Increase in bench height by 20% to existing bench height improved fragmentation. Increase in stemming column reduced ground vibrations and noise pollution. Change of straight pattern of holes to echelon and use of multidelays improved the throw. Above changes in blast design reduced boulder formation by 79% and reduced consumption of explosives by 20% mainly because of reduction in secondary blasting.
- OSTI ID:
- 398359
- Report Number(s):
- CONF-9502142-; TRN: IM9649%%567
- Resource Relation:
- Conference: 11. annual symposium on explosives and blasting research, Nashville, TN (United States), 5-9 Feb 1995; Other Information: PBD: 1995; Related Information: Is Part Of Proceedings of the eleventh annual symposium on explosives and blasting research; PB: 348 p.
- Country of Publication:
- United States
- Language:
- English
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