An auger is a spiral flighted tube, with hexagonal connections at each end. The tube is designed to drive a cutting head through the earth while extracting the soil along the helical coils for removal at the entry pit. Augers are used in the technique of auger boring, which is used to install piping underground without digging a trench.
Trenchlesspedia Explains Auger
An auger is the drive component of a set of auger boring equipment which also consists of an auger machine, cutting head, steel casing pipe, and tracks or cradle. The auger connects to the auger machine on the one side, which provides the thrust and rotation, and to the cutting head on the other, which drills through the earth. The auger is located inside the steel piping so there is little danger of settlement issues once the process is complete.