ABSTRACT
Face and crown collapses occurred frequently in the Iwabuchi volcanic rock formation during TBM excavation of the pilot tunnel. Figure 1 shows the elevations of loose areas above the crown of the pilot tunnel at different points. The red dotted line indicates the elevation right after excavation and the blue solid line represents the elevation at the end of displacement after sufficient time passed since the TBM passed the point. The value along the red line is more than double that along the blue line at STA. 1045 70. The expansion of the loose area and more crown collapses were of concern during the enlargement of the pilot tunnel. Applying auxiliary methods according to the
ABSTRACT: In Fujikawa Tunnels, the TBM pilot and enlargement tunnel excavation method was applied on this project. The pilot tunnel was firstly driven by a hard rock TBM with providing vital information for subsequent tunnel enlargement work.
