The Petrographic and Geotechnical Properties of a Dolerite Intrusion in the Assessment of Its Blasting Performance at the Magdalena Colliery, Dundee, South Africa

The presence of dolerite intrusions in underground collieries often causes damage to mining equipment, delays in mining schedules and loss in production. This is often exacerbated by inadequate pull from the blasting operations along the intrusion. Thus, the proficient removal of dolerite intrusions through efficient blasting techniques play a vital role in the economic output of a colliery. This study is focused on one such intrusion within the Magdalena Colliery, wherein a 13.88 m dolerite dyke resulted in the replacement and displacement of the Alfred seam. Selected sampling was conducted along the length of the intrusion in order to determine the petrographic and geotechnical properties influencing the blasting performance of the dyke. A detailed petrographic analysis was done by analyzing thin sections of the dolerite in order to identify the major minerals present. X-ray diffraction (XRD) analysis was also conducted to determine the percentage composition of minerals along the intrusion. Geotechnical tests were also conducted in order to assess the technical properties of the dolerite. The geotechnical tests conducted included point load test, sound velocity test, uniaxial compressive strength test and Brazilian disc strength test. The study conducted demonstrates that a strong correlation exists between the blasting performance and geotechnical and petrographic properties of the dyke.