Pipe umbrella drilling method

摘要

The invention provides a drilling device suitable for production of a support pipe-lined drill hole for the pipe umbrella technique wherein the device comprises:
a body (4);
a pilot drill bit (2) for drilling a pilot hole (35a);
one or more drill elements (3) for radially enlarging the pilot hole by drilling to apply a rock loosening force (FG, 27) having a radial component (FGR) and an axial component (FGA) wherein the one or more drill elements are mounted on the body so that the one or more drill elements may be extended or retracted from the body and wherein the one or more drill elements are arranged so that the radial component (FGR) of the rock loosening force is such that the one or more drill elements are prevented from retraction during the drilling; wherein the device operates consistently independent of the rock conditions and ensures the production of bores 35 that are always of the same cross section.