The extra long tunnels need the rapid excavation potential of modern TBM technology. However, because of high overburden or rock cover, especially in the complex geology or seabed, it is often difficult and not economical to study the geology properly and to get a good insight of what to expect in advance of TBM boring. Pinglin TBM tunnelling is the first and crucial trial in Taiwan in terms of the future decision-making. The eastern section of Pinglin tunnels is situated within the fold-and-thrust belt structural region in Taiwan, due to continent-arc collision and plate tectonic setting. Geological problems center mainly on very hard, brittle, blocky and abrasive quartz sandstone interrupted by frequent fault zones and greatly crushed shear planes harboring high volumes of ground water. A pilot tunnel ( ∮ = 4.8m ) and two main tunnels ( ∮ = 11.74m ) apply TBM technology. This paper presents our experience about geological hazards and remedial measures in Pinglin main TBM tunnelling.
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