ANALYTICAL STUDY TO DETERMINE OPTIMUM INTERVALS BETWEEN SUCCESSIVE CONSTRUCTIONS IN THE MULTIPLIED TUNNEL SUPPORT SYSTEM

Abstract

To prevent large deformation in the Iiyama Tunnel of the Hokuriku Shinkansen, NATM supports were erected twice in succession at the same location. This method is called the Multiplied Tunnel Support System. In this paper, the optimum time interval between construction of the first and second supports was derived analytically by FEM using the estimated creep method. The research reinvestigates analysis using the equivalent elastic modulus of shotcrete. The interval of construction at the site was 12 days, which was very near the ideal interval derived by analysis.