Eight giant tunnel boring machines (TBMs) are ready to start carving 42km of tunnels across London for Crossrail. Experience can be learned from Taiwan's Hsuehshan tunnel project, one of the toughest project's ever. Tunnelling through Taiwan's Hsuehshan range involved navigating folds and cracks in rock and quartz, and huge amounts of underground water. During the first 18 months of digging the tunnel collapsed nine times. Rock fractures constantly crippled the TBM, while surging groundwater often flooded the work site.
