Abstract: For burying piping (1) in a sea-bed, at least one excavating machine (3) is provided for forming a first trench (4) parallel to the front portion (1.sub.1) of the piping and to a guide formwork (5) adapted both for moving parallel to the first trench (4) and for then forming automatically, during its horizontal advance, a second trench (8) parallel to this first trench, contiguous therewith and extending planewise in the extension of the front piping portion, said structure having for this purpose an oblique front moldboard (9) which pushes back laterally into the first trench the earth engaged thereby and for automatically burying the piping (1) in the second trench (8) thus formed.