Design of Controlled Pre-Split Blasting in a Hydroelectric Construction Project

Geologic conditions and design requirements around upstream Nachtigal Falls, in Cameroon, for the hydroelectric construction project on Sanaga River dictated close control of blasting procedures with very precise geometry to obtain safe economical excavation lines. Various techniques pre-split were used initial stage all major excavations. Hole diameters pre-splitting 89 mm, hole spacing ranged from 0.8 1m. Explosive charges varied 1 7 kg per hole, detonating cord linear charge 12 60g. The contour technique is aimed at controlling overbreak improving remaining slope stability. Over-break or over-excavation needs be controlled since its occurrence compromises operations terms safety (instability slope; loosening rocks that increase risk operational people; an irregular free face subsequent blasting); costs (need reinforcement rock structure through costly sustainment systems; concrete volumes civil works). This paper discusses detail field implementation blasts successfully carried out achieve clean vertical walls moderately dipping, though complexly sheared jointed gneiss. Based results experiments, we able a pattern both experimentally cost-effective manner. It felt methods developed this could have useful applications other projects. Doi: 10.28991/CEJ-2023-09-03-05 Full Text: PDF