Flyrock risk prevention in open pit blasting

Abstract

Norcem limestone quarry at Bjørntvedt has neighbours and infrastructure close to the quarry. Elimination of the risk of flyrock from blasting is thus of great importance to the operation. For drill hole dimension 3,5? ? as used at Bjørntvedt -the risk zone of flyrock is considered to be between 600 and 700 m from the blast. It is recommended to cover the blast if there are sensitive installations or people inside this radius. If no cover is used, adequate alternative preventive measures must be documented. The guidelines recommend that the first row of drill holes is surveyed to control the distance to the bench front, prevent too high specific charges and to detect joints and weak zones.Bjørntvedt has documented drilling and blasting procedures in place to prevent flyrock. These procedures do not at present include surveying of drill holes/face wall or covering of the blast.The master thesis will use the 6 sigma methodology to analyse the problem of flyrock risk elimination at Bjørntvedt. The thesis will include a description of the problem, the current procedures and the blasting results with respect to flyrock.