US Patent 7389831 Dual-member auger boring system

A system for boring horizontal boreholes and installing products using a dual member drill string. The system is comprised of a boring machine with a frame and a rotary drive supported on the frame, a downhole tool, and a dual member drill string. The drill string comprises an inner member disposed within a tubular outer member such that the inner member is rotatable independent of the outer member. The outer member has at least one helical projection supported on an exterior surface of the outer member. The projections on the outer member function as an auger to clear spoils and support the bore. The auger arrangement with the dual member drill string can be used in forward reaming or backreaming operations.