ABSTRACT
Tunnel Boring Machine (TBM) has been widely used in long tunnel excavations in many countries for its advantages in speed, price, and safety. However, there are some difficulties, risks, and challenges in TBM excavation. When encountering grounds of fault, fracture zone, water ingresses, or ground with high variation in rock strength and lithology, collapses may trap TBM frequently. Such incidents decelerate TBM advancing and raise project expenses in most of the case. This manuscript introduces experiences from two tunneling cases, Hsuehshan tunnel, the longest road tunnel in Taiwan with a 12.9 km length, and Tsengwen tunnel, the hydraulic tunnel of the highest overburden 1300 m in Taiwan. Releasing methods carried out in the cases, including top heading tunnel, bypass tunnel and others, and measures to prevent further TBM jam, such as forepoling and ground improvement are presented here for future TBM excavations in long and deep tunnels.
