A system includes an excavation assembly, which in turn includes a supporting body having a perimetric edge defining a closed path. A distribution apparatus protrudes transversally relative to the perimetric edge and is movable in a guided manner on the supporting body. The distribution apparatus transversally distributes a quantity of hardenable or solidifiable material towards the outside of the perimetric edge, so as to be able to lay a plurality of axially superimposed annular layers(s) of the hardenable or solidifiable material defining a tubular structure (T) around the excavation assembly. A motor device moves the distribution apparatus on the supporting body.