Drilling and extending of blind mine-shafts - involves initial drilling of hole from lower shaft and widening it with larger drill

摘要

An advance borehole is enlarged to the size of the blind shaft by means of a drilling unit powered from below via a linkage and consisting of individually driven disc-shaped cutting rollers. The shaft lining is installed via a platform independently of the drilling process. The shaft column comprises four part rings made of profiled beams which are encircled by a sheet lining. They are assembled on an erection platform on the upper blind shaft surface and connected section-by-section to the shaft column as the drilling unit advances. After each advancing step, the shaft platform is braced against the wall of the blind shaft. After completion of the enlarged shaft, concrete is placed behind the structure against the shaft wall.