The influence of weak rocks on excavation and support of the Beykoz Tunnel, Turkey

Tunnelling in very weak rock associated with major faults requires the considerable use of a combination of support systems such as shotcrete, rock bolts, wire mesh and steel sets to stabilise the tunnel. Forepole, drainage, face supporting body, reducing of excavation step and sequence excavation play critical roles in reducing failure potential. All of these support measures are aimed at improving the strength and stiffness of the weak-rock mass in order to use its load-sharing capacity.