METHOD OF HEAT DRILLING OF HOLES IN ICE AND APPARATUS FOR CARRYING OUT THE METHOD
The major field of application of drilling in ice is polar research with through-bores in floating ice for examining the lower surface of the ice, the water below it and the bottom of the sea. Melt drill heads or wash drill heads operating wi th hot water are used for heat drilling which, however, can only wash out bore hole diameters in the range of he diameter of the drill and. Therefore, render th e lowering and hoisting of drills and measuring apparatus very difficult. For forming uniform and large bore diameters the method in accordance with the invention, therefore, provides a combination of the melt drill and the wash drill, wash drilling taking place in the radial plane of the bore hole, and for thi s purpose uses a melt-wash drill head (1) which at its top is provided with a water inlet (2), a hemispherical melt section (3) below and a narrow azimuthally circumferential annular gap (5) connected by large surfaces with the water inlet (2), through which gap (5) the hot water (4) is guided against the wall (7) of the bore hole and deflected upwardly so that a smooth surface (14) of the bore hole and a constant bore hole diameter (15) result. The melt-wash drill head (1) closes a pilot bore hole (9) with a film (12) of melt water to prevent cold sea water from being sucked in atthe end of the main bore hole (19).