They are rigs preapered to advance by jacking the big diameter pipe. This pipe is made of reinforded and holded concret or metallic. The front cutter head is like an open shield with front cutter head is like an open shield with a boom armed with a rotary cutter, or grazer, or retro type bucket.
They are designed to advance drilling and jacking pipe simultaneously. They use diameters from 1500 mm to 3000 mm and they work crossing underneath roads, railway, hills, etc.