ABSTRACT
This report describes the design method of the secondary lining in squeezing rock zone. Tagami tunnel is a 6,988m long tunnel in the Kagoshima route of Kyushu Shinkansen. At the location of 2200–3000m from the south entrance, tunnel face condition turned suddenly to very poor. Convergence measurement showed up to 300 mm reduction of upper half cross section and the serious damage of supports were observed. Back analysis using Finite Element Method based on the measured displacement was carried out in order to clarify the mechanical properties of the weak zone.
Due to the large displacement of tunnel supports, replacement of supports was executed and tunnel section was closed as soon as possible using more stiff supports. After the completion of tunneling, rock has been showing very small but continuous creep behavior. Therefore the concrete lining for this zone was designed considering the long-term lord.
