Development of Traveling Protector for Enlargement of Live Line Tunnel by Drilling and Blasting, and Application to Shikishimanai Tunnel Project (Route 229)

Abstract

Technological development for the enlargement of existing tunnels is increasingly required to cope with problems related to traffic congestion, partial amendments of the Japanese ordinance of the public road structures and out-sizing of freight vehicles. There are cases, when the tunnel traffic must be maintained through existing tunnels during their reconstruction due to non-availability of detours, even for widening hard rock tunnels. Then, excavation by drill and blast is desired for widening such tunnels. Enlargement of live line tunnel method (ELLTM for short) is a tunneling method that adopts a traveling protector (staging) which can endure the impact by drilling and blasting. By the ELLTM, reduction of construction cost and time can be achieved. It is applicable to various geology and tunnel lengths. This paper reports on outlines of the ELLTM and the Shikishimanai tunnel project which used the ELLTM.