Economic and technological assessment of shaft sinking by conventional hand held drills contrasted with rig mounted mechanised drilling methods

This is a case study concerning two shafts of slightly different diameters, both being sunk during similar time frames on the Witwatersrand, one being sunk with a seven boom drill rig and one with conventional hand held rock drills. The paper contains a description of the shafts. That portion of the sinking cycle from the blow over and examination of the bottom, scribing of croppers, drilling charges up and blast is described for each method and shaft. The cost comparison data were collected in the upper portion of the shafts before the station construction and development phases of the projects began and contaminated the sinking comparisons. The salient points of the comparison tabulated. The data are then adjusted for points of difference and reduced to a common denominator for purposes of the exercise. A costing exercise then follows for the two cases. Areas where cost differentials exist are compared, summarized and brought to conclusion.