HIGH PRESSURE WATER JETS AID TBMs.

Performance improvement of cutter discs by the assistance of high pressure water jet was found to be a proportional function of the hydraulic capacity installed. In the case of tunnelling machines for diameters of 6 to 7 m this function theoretically results in electric drive capacity requirements which, if met, would entail serious technical and human engineering problems for tunnelling in underground mining operations. By systematic evaluation of full scale tunnelling tests conducted for the purpose, all the possibilities for optimisation of this combined tunnelling technique were evaluated. Tunnelling advance in time, rotational speed of the drillings head, advance force and cutter depths are of essential importance in this respect. Further investigations were carried out to obtain relatively good heading rates by selective, high pressure water jets on particularly defined areas of the tunnelling head. In addition, successful and cost effective application of additives to high pressure water are discussed. A comprehensive discussion considers the technical and economic possiblities and the recognisable limits of this technology.