Measurement of blast-induced rock movement in surface mines using magnetic geophysics

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 on the surface of a blasted rock-pile, before excavation. A method has been developed and tested to accurately measure the direction and magnitude of sub-surface blast movement. This technique uses a cesium vapor gradiometer and a real-time differentially corrected GPS system, to locate the post-blast position of magnetically enhanced target objects placed within blast holes inside a bench. The procedure developed does not require the blasted rock to be disturbed and the movement information is available in sufficient time to allow modification of the selective mining boundaries for each surveyed blast. It was found that the maximum depth of target detection was 70 feet; with the overall accuracy being measured as...