A NEW CONSTRUCTION METHOD FOR WIDENING HIGHWAY AND RAILWAY TUNNELS

摘要

The idea of widening highway tunnels while they are in operation was first thought of by Societa Autostrade engineers as early as the start of the 1980s when the need first arose to widen highways to three lanes and to add an emergency hard shoulder. Studies were undertaken in some technical environments with the aim of producing a universal methodology for use in all types of rocks and under all conditions. For grounds with poor cohesion, however, the diffusion of the pre-cutting technique has so far made it possible to actually implement a widening method, above all by resort to a secondary lining in reinforced concrete, prefabricated segments made active by special jacks fitted in the key segment (active arch method).