It was found from researches on construction cases in Japan and overseas that one of the most effective tunneling methods for a large section tunnel with shallow overburden is installing the roof to stabilize the section against the overburden before excavating the ground. Examples for installation of tunnel-roof are connecting several small-section tunnels, which is common in China and France, utilizing a box-shield and combining shields by means of the shield-tunneling technology that is remarkably improved, and NATM.
In this paper, these tunneling methods are proposed and their effectiveness, advantage and disadvantage, applicability, and cost efficiency are reported.
