Abstract
Hida tunnel is a 10.7km long highway tunnel. It has been excavated by a large cross section NATM in poor ground with high overburden (more than 600m now). This excavation method will be continued to the planned boring commencement location of the 12.84m diameter TBM.
A large displacement during the main tunnel excavation in poor ground was anticipated. Using the measurement data of the pilot tunnel in this section, the initial support system structure and its displacement of the main tunnel during excavation were analyzed by F. E. M. and its results were applied to the main tunnel execution. The excavated tunnel section of each stage was closed with temporary invert at adequate timing, if its displacement is anticipated to be larger than estimated value. The combination of measuring, numerical analysis and feed back of measured data to the execution method made the actual displacement of the main tunnel smaller than estimation successfully.
