AUGER BORING, (or THRUST BORING)
It is extremely rare for the Pipeliners to actually dig a road, footpath or stream. Unless conditions like rock prevent it, they will invariably bore the pipe under the obstruction. Here they are boring 4 metres below a possible Roman Bathhouse.
They use three methods of boring, and auger bore, concrete sleeve tunneling and HD drilling. The simplest method is an auger bore, as shown here.
First a sideboom drops the auger engine into a prepared bellhole. Note the auger bit installed in the pipe ready.
After the pipe has been drilled through, the auger bits are removed and the pipe tied-in to the mainline. There is no sleeve used in this method.