TRACTION BORING DEVICE USING MULTIPLE TREPANS FOR PRODUCING LARGE CUTS IN CONCRETE WORKS AND THE LIKE AND METHOD OF PRODUCING CUTS

摘要

A multiple trepan boring device (D, D') for producing substantially large cuts (C) in large works (W), such as concrete dams, comprises a drilling shaft (24) adapted to be translationally displaced along its longitudinal axis and carrying a series of spaced apart cylindrical rotatable trepans (30) each having a peripheral cutting surface (32) and an annular cutting surface (34, 69), the latter extending in plane perpendicular to the axis of the drilling shaft (24) and radially between the shaft (24) and the peripheral cutting surface (32). Weights (40) apply continuous downwards forces on the shaft (24) and thus on the trepans (30). With the trepans (30) resting on the top of the work (W) to be cut, the trepans (30) are rotated in place, and under the aforementioned forces the peripheral cutting surface (32) of each trepan (30) bores a hole until the drilling shaft (24) rests on the top of the work (W). Then the shaft (24) is displaced translationally while the trepans (30) continue to rotate thereby causing the annular cutting surfaces (34, 69) to remove a layer of the work (W) extending between the shaft (24) and the peripheral cutting surface (32). This procedure is repeated so as to produce a cut (C) of a width corresponding to the outside diameter of the trepans (30) by successive removal of crescent-shaped layers from the work (W). After the removal of each layer, the shaft (24) is lowered along a distance corresponding to the difference in radii between the drilling shaft (24) and the trepans (30).