11.11 Lock approaches
Lock approaches provide the transition between the navigable river and
the lock and must be designed both to ensure a safe and speedy entry into
the approach basin and the lock and to permit the mooring of boats
waiting to enter the lock while this is operating to pass other vessels down
or upstream. The approach basin width will thus depend on the above
factors as well as on the number of locks (single, twin, etc.) and the likely
number of push trains waiting for handling.
On a waterway with flowing water the approach basin is divided into
three parts (Fig. 11.18). The first part lais intended for the braking of the
vessels entering the lock or for their accelerating at departure. The next
partlbis intended for passing and overtaking of vessels or push trains, and
possibly for their mooring. The third part lcwith jetties or guide walls (at
inclinations of 1 in 4 or 1 in 5) represents a transition between the wider
approach basin and the narrower lock head.
The approach basins of locks on canalized rivers are usually sepa-
rated from the power plant or weir by a long dividing wall or an island. A
sudden change of the width and cross-section here results in critical flow
regions with lateral contraction, and transverse or even reverse flow; these
conditions are very unfavourable for navigation and may cause accidents.
To reduce the transverse velocity below the maximum permissible value of
about 0.35 m s^1 it is advisable to provide a water passage in the dividing
wall near its head (Fig. 11.18).
490 INLAND WATERWAYS
Fig. 11.17 Inclined boat lifts (Cˇábelka and Gabriel, 1985)
