ABSTRACT
Iiyama Tunnel for Hokuriku Shinkansen (a bullet train line) runs through the boundary of Nagano and Niigata Prefectures and has a great length of 22.2 km. It is divided into six work sections for construction. In Itakura and Konari work sections, 3,660 m and 3,800 m in length respectively, that locate first and second from the Niigata-side portal, we encountered the squeezing phenomena in mudstones of Miocene, Neogene formations. The maximum convergence tended to exceed 200 mm especially in sections whose overburden went beyond 180 m. In our previous paper (Kemmochi et al., 2004a & 2004b), the application of the multiplelayer supporting method in squeezing rocks in Konari work section was reported. The characteristic behaviors of the first-layer support members especially on the stress variation were investigated with the in-situ measurements and three-dimensional numerical anal yses. Consequently, it was found that the behaviors of the convergences and support stresses were able to be expressed by the numerical analyses in which the work execution procedures were fully sequentially incorporated.
