ABSTRACT
The 3260 m Bolu Tunnels constitute the last section of the Anatolian Motorway from Istanbul to Ankara to be completed. The tunnel alignment crosses severely disturbed ground in the immediate vicinity of the North Anatolian Fault Zone. After severe problems were encountered during excavation due to the highly squeezing nature of the ground, the tunnels were subjected to a redesign involving sophisticated numerical analyses based on an intensive ground investigation program including a pilot tunnel.
