Abstract: A method of building a strengthened embankment body which involves the steps of repeatedly burying first nets and embanking and roll-compacting the body being built on ground until a required height of embankment is reached, repeatedly burying of second nets between the buried first nets and embanking and roll-compaction of compression-resistive materials are concurrently repeated to form a highly strengthened arched body part locally at a zone corresponding to an arched peripheral wall of a semi-cylindrical tunnel to be excavated through the body, the first buried nets providing the stability of the entire embankment body while the second buried nets achieving the stability at the arched peripheral wall zone of the tunnel.

Abstract: A method of building a strengthened, embanked foundation capable of forming therein a tunnel comprising steps of burying, during embanking work of lower part of the foundation, a plurality of nets as vertically spaced in embanking material for the foundation at least in its internal zone including side wall portions of the tunnel later formed so as to substantially horizontally intersect imaginary sliding surfaces occurring in the portions upon excavation of the tunnel, forming a crushed-stone arch layer overlying from both upper side portions to upper central portion of the later formed tunnel during further course of the embanking, work providing a hanging support to ceiling wall portion of the later formed tunnel as coupled through hanging rods to the arch layer during its formation, and, after completion of the embanking, excavating a zone defined by the side and ceiling wall portions in the embanked foundation to form the tunnel therein.

Abstract: A method of building a hollow structure in an embankment during its embanking work, wherein portions inside the embankment which are to form slope or side wall layers of later excavated cavity for the structure are embanked simultaneously with remaining portion of the embankment, with a plurality of nets buried as vertically spaced and to substantially horizontally intersect sliding surfaces appearing in said layers upon excavation of the cavity, upper ceiling portion of the cavity later excavated is prestressed during further embanking work by means of at least crushed stone filling between supporting plates buried respectively above each of said slope layer portions as opposed to each other with their surface and coupled by steel wires tightly hung between them, and after completion of the embanking work the cavity is excavated by removing embanked material in a zone surrounded by the slope layer portions and prestressed ceiling portion, so that the structure can be built within the cavity with the slope la