ABSTRACT
An innovative tunneling method called LTM, or Lee’s Tunneling Method, is a kind of TBM/NATM combined method, in which drilling and blasting for enlargement of pilot tunnel as well as construction of concrete lining can be carried out simultaneously during the excavation of pilot tunnel by TBM. Tunnel construction can be completed in the shortest period, whereas in conventional method, the blasting for enlargement is possible only after the pilot tunnel is passed through. From the test construction, it is verified that the excavation by TBM and the blasting for enlargement are possible simultaneously, by moving equipment required for TBM such as electricity supply cables on to the rail system and protecting them with the carrier which is installed at the lower half section of pilot tunnel. In addition to this, vibration and noise at ground surface can be reduced by 15% or more. Therefore, the LTM can be applied effectively in urban areas or long tunnels with length of 1 km or more.
