Abstract:

Taiwan, TaipeiI Lan Expressway Hsuehshan Tunnel, in length of 12.9km, composed of 2 main tunnels (westbound and eastbound) with boring dia. 11.74m and a pilot tunnel with boring dia. 4.8m which were originally planned to be bored by Tunnel Boring Machine (hereinafter called TBM).  Due to the tunnel is located at convergent boundary between the Eurasian plate and the Philippine sea plate along with a great amount of underground water, no matter excavate by Drill & Blast method or TBM method, it may easily cause a disaster, the more bigger crosssection will be the more dangerous, therefore, cautious and proper planning of how to cope with the difficult situation and select a proper TBM prior to the construction, vigilance against any situation during the construction, prompt and correct reaction when a disaster occurs...etc. are the great important issues in this project, so that to keep the damage from atrociously ground and inrushing water to the minimum.  Especially in the geologically structure, most of faults are distributed in 3.6km southern part of the tunnel, the breadth of faults are even reached to 50 meters above, however, in view of the environment constrain, water drainage during the construction, portal facilities area and mucking delivery...etc. all 3 tunnels were originally planned to be bored by TBMs from the southern portal (Touchang) to the northern portal (Pinglin), it pass under the Hsuehshan Ranges in northern Taiwan, in the tunnel horizon, it cut across strong, hard, abrasive and intensely fractured Szeleng Sandstone on the south and indurate sandstone and siltstone on the north, the entire zone heavily affected by tectonically movement is very much faulted and bears a great amount of water, the TBMs actual faced ground conditions were more worth than ever expected.  This paper presents our methodology and experience of Hsuehshan main tunnel TBM mining operation in such poor geological ground condition, provide to the tunneling and underground construction field experts for references, with the hope that technology and technical know how as well as construction management in connection with TBM operation under such ground condition will gain more further development and improvement.

Key words: tunnel boring machine  , poor geological ground condition  , faults