Chainage The length along the longitudinal direction of tunnel Crown The top portion of tunnel is crown. It can be circular,semi-circular or rectangular in shape. Side/Wall The side portion of tunnel. It is generally vertical. Bench The bottom part of tunnel left after the excavation of heading is said to be bench. Excavation of face in done in multiple step for large cross sectional area. Invert The lower portion of tunnel Portal The entrance of tunnel is portal. Heavy support […]