Abstract
RC columns supporting the ceiling slab of Daikai subway station, a box tunnel constructed using the cut-and-cover method, totally crumbled in the 1995 Hyogo-ken-Nanbu Earthquake; that failure was followed by a couple of meters subsidence of its overburden soil over the entire 90m extent of the crushed station. This damage stimulated a sharp rise in research activities for possible measures for avoiding that fatal destruction. Among a variety of tunnel members, center columns sustaining the weight of overburden soil are the most important key members, and therefore should not be destroyed. Insertion of a flexible joints on upper and/or lower ends of these columns would be a possible measure. This paper presents a possible shape of a column joint that will meet the necessary requirements for the device sustaining a heavy oveburden soil mass and reducing the induced shear force and moment.
