Blast movement measurement to control dilution in surface mines

CIM Bulletin, Vol. 94, No. 1047, 2001

G.W. Harris, P. Mousset-Jones and J. Daemen, Mackay School of Mines, Reno, Nevada

To minimize ore dilution induced by blast movement in surface mines, it is necessary to quantify such movement. This will enable more accurate location of the grade boundaries beneath the surface of a blasted rock pile before excavation. A method has been developed and tested to accurately measure the direction and magnitude of subsurface blast movement. This technique uses a cesium vapour gradiometer and a real-time, differentially corrected GPS system to locate pre- and post-blast position of magnetically enhanced target objects placed within blastholes inside a bench. The procedure developed does not require the blasted rock to be disturbed, and the movement information is available within a sufficient time to allow for modification of the selective mining boundaries for each surveyed blast. It was found that the maximum depth of target detection was 18 m, with the overall accuracy being measured as ±1 m (horizontally) and ± 1.2 m (vertically).

Keywords: Ore dilution, Blast movement, GPS (Global Positioning System), Field magnetics, Vertical gradient.