Method of forming concrete pilings using a reverse circulation drilling system

Abstract

A method of boring a hole in which a down hole hammer is pneumatically operated to form a hole, and a cementous material is injected into the hole through a passage in the down hole hammer.

1 . A method of boring a hole: 
 providing a down hole hammer comprising a driver; a pilot bit rotatably coupled to the driver, the pilot bit having a shank, a peripheral drilling surface, a lower surface, and a bore extending from the lower surface generally upwardly through the shank; a plurality of underreamer arms rotatably mounted intermediate the driver and the pilot bit and including underreaming surfaces, the underreaming arms having an extended position wherein the underreaming surfaces are positioned concentrically outside the pilot bit perimeter; cam surfaces engageable with the underreamer arms for urging the underreaming arms into their extended positions, for locking the underreaming arms into their respective extended positions, and for retracting the underreamer arms responsive to rotational movement between said driver and said pilot bit; and    surfaces defining at least one air passageway between an outer surface of the driver and the bore in the pilot bit;    the least one fluid passageway in communication with a source of a cementous material and at least one said cam surface, and further including a valve operable to discharge the cementous material to said at least one cam surface;    operating the downhole hammer to bore a hole; and,    discharging cementous material into the hole.    
     
     
         2 . A down hole hammer comprising: 
 a driver;    a pilot bit rotatably coupled to the driver, the pilot bit having a shank, a peripheral drilling surface, a lower surface, and a bore extending from the lower surface generally upwardly through the shank;    a plurality of underreamer arms rotatably mounted intermediate the driver and the pilot bit and including underreaming surfaces, the underreaming arms having an extended position wherein the underreaming surfaces are positioned concentrically outside the pilot bit perimeter;    at least one cam surface engageable with the underreamer arms for urging the underreaming arms into their extended positions;    surfaces defining at least one air passageway between an outer surface of the driver and the bore in the pilot bit; and,    the least one fluid passageway in communication with a source of a cementous material and at least one cam surface, and further including a valve operable to discharge the cementous material to the at least one cam surface.    
     
     
         3 . A downhole hammer according to  claim 2  further comprising: 
 the at least one cam surface including at least one surface for locking the underreaming arms into their respective extended positions.  
 
     
     
         4 . A downhole hammer according to  claim 2  further comprising: 
 the at least one cam surface including at least one surface for retracting the underreamer arms responsive to rotational movement between said driver and said pilot bit.