Abstract:

The low bench blasting is usually used in the blasting works on the surface during the specific conditions at the working sites. This case study was carried out at KT2 construction site, Huoi Quang hydro-electric project in Vietnam with the aim to define optimum burden for the blasts in 2.5 m bench height. In this study, due to the ratio of bench height to borehole diameter K/d is 32,9 (for normal bench blasting K/d ≥ 60, the value of burden cannot be determined by traditional equation for normal bench blasting. Therefore, a series of single hole test blasts was used the same bench height and the charge weight was kept unchanged for defining the optimum burden. This method brings many encouraging results when the maximum value of burden was obtained with maximum broken volume, minimum specific charge and even good fragmentation and acceptable toe condition.