Drivage with freeze-boring in mines and tunnels uses double headed machine to drill outer and inner strings into rock leaving outer string and bit to case hole for piping in circulating freeze agent.

摘要

The outer string (13) of the freeze bore drill and the drillbit (15) remain in the rock to seal off the back end of the bore, and a narrow bore plastics tube fitted with spacers is then run in to complete the circulation path once fixed in place and charged with freezing agent. The drilling machine (10) with carriage (11) drives in the outer (13) and inner (14) strings via associated drillbit (15). The outer string (13) pipes (18,19) are coupled by a metal connection and the inner string (14) is releasably joined to the inner bit (16) as enclosed by the outer bit (17) of the drillbit as such (15) and a bung introduced into the outer string pipes seals the outer string both inside and out. The machine (10) should be of the double headed type and the inner bit (16) and inner string are releasably joined by a bayonet fastener.