The development and trialling of a cement grout blasthole stemming enhancement cone

This paper discusses the development and field testing of a Stemming Enhancement Cone (SEC) for its potential introduction into the Eastern Goldfields of Western Australian surface mining operations. The function of the SEC is to improve blasting efficiency by enhancing the effect of the stemming in the blasthole thereby reducing the associated mining costs. For these trials the SEC was constructed of a high early-strength cable bolt grout. The SEC unit was a solid cone placed just above the explosive column within the stemming. The SEC was trialled at the bottom of an abandoned section of an open pit operation in transition sulphide ground conditions. Only crater blast configurations were used and all test holes were nominally 3 m deep and 76 mm in diameter. Test measurements included motion analysis using video techniques, crater or mound profile using manual methods and full waveform airblast monitoring. The SEC has the effect of increasing the surface area affected by the blasthole and locking the stemming into the blasthole for a longer period of time when compared to normally stemmed blastholes. Furthermore, the holes containing SEC generally had lower airblast levels and low ejection heights. The major conclusion is that the introduction of a SEC for routine open pit gold mine blasting is not recommended.