New Findings Gained in Blind Shaft Boring at the Zollverein Mine

摘要

After using the blind shaft boring machine GSB-450/500 from A. Wirth and Co. KG twice in relatively mild rock formations, the sinking of the bored blind shaft at the Zollverein mine furnished the proof that even with the reconsructed prototype of this machine, boring rates of up to 19.5 m/d, with average rates around 10 m/d, could be achieved in hard, abrasive rock. Downtimes during the boring operations were attributable mainly to the high degree of wear of the cutting rollers, due, in part, to the high content of sandstone and, in part, to the secondary crushing of the cuttings on the borehole bottom, as well as by leaks in the hydraulic system of the shaft boring machine. The costs of the bored blind shaft are compared to the costs of a conventionally sunk blind shaft of the same depth, standing in the same geological formation, but having a diameter 0.25 m larger than the bored blind shaft. The additional cost of DM 226,000 of producing a bored blind shaft versus a conventionally sunk one is, at 10% of tota costs, still relatively low. In view of certain cost-reduction possibilities, a minimization of the cost difference in favor of the bored shaft can be expected.