15 August 2002
usually provided in the walls of drydocks. Sometimes, these tunnels may be eliminated
or made of nominal size if flooding is accomplished through a floor culvert near the
entrance and the intake to the main dewatering pumps is also through the floor.
Large Docks. For larger docks, even if flooded and dewatered as stated
above, a small tunnel and/or system of sumps may be advisable for final stripping of the
water from the floor.
Tunnel Design. In all cases, the tunnel should be made as small as is
compatible with hydraulic requirements. Large tunnels should never be less than 6 ft
high. Except for pure gravity walls, drainage tunnels present structural problems and
result in increased cost. Tunnels should be located in the walls in order to create the
most favorable stress conditions.
Crane Rails. Place one crane rail on top of the wall as close to the
centerline of the drydock as possible and compatible with other wall and tunnel design
considerations. Never place the inboard rail nearer than 1.52 m (5 ft) to the edge of the
coping. Rails should be set with the top flush with the concrete surface. The
companion rail is generally located off the wall structure and supported independently.
For additional criteria regarding location of crane rails, refer to Chapter 8. For details of
rail supports and portal crane trackage, refer to MIL-HDBK-1005/6, Trackage.