| Abstract: | The development of a large-diameter (from 500 m and more) rotary drill tool (drill bit) for exploration of placers in permafrost is discussed in the article. It is shown that at the contact of drill bits and bottomhole, permafrost thaw takes place with the further adhesion and congelation of the drill tool and hole walls, which degrades coring. The dependence of heat emission at bottomhole on cutter configuration radius on drill bit is determined. The developed design of a drill bit ensures efficient destruction of bottomhole with minimized heat emission, and a prototype drilling assembly is manufactured for large-diameter rotary drilling. The in situ test data are presented. |
