Abstract: A construction method for widening road, superhighway or railway tunnels, without interrupting the traffic flow includes a first stage of excavation; in steps, of the ground between the theoretical profile of the future widened tunnel and that of the original tunnel, after having reinforced the ground between the theoretical profile of the future widened tunnel and that of the original tunnel by reinforcement operations on the face, and a second stage in which the final lining, comprising one or more arches of prefabricated segments is placed close to the face.

Abstract: Prefabricated concrete assemblable elements are fastened together so as to form a light cellular leading structure with high resistance. The elements can be three-dimensional, box-shaped or angle-shaped, or they can be of a two-dimensional board type, provided with connection joints at their edges. A lower slab and an upper slab, preformed or laid in situ, complete the embankment and allow the elements to cooperate.

Abstract: The method comprises the steps of driving into the ground a plurality of adjoining tubes and coupling these tubes by suitable variable interaxis structures for making a monolithic strong covering or cellular arch.