Abstract: A method of forming a passageway (P) through the ground by inserting into the ground a structure (1) comprising a superstructure (3) and a substructure (2). The superstructure (3) is inserted into position in the ground, and the substructure (2) is urged into the ground beneath the superstructure (3), the ground being excavated as the substructure is inserted so as to form the passageway (P) bounded by the superstructure and the substructure.