UFC 4-150-06
12 December 2001
The radius of the curve must fulfill the above criteria. Once R has been
determined, the channel-bend geometry must be determined. This consists of widening
the channel at the bend and providing a smooth transition from the straight portions of
the channel through the curve. This can be done in several ways, as shown in Figure
5-20 to Figure 5-24. The entire amount of widening in the channel could be added to
the inside of the channel, as shown with curved transitions in Figure 5-21 and straight
transitions in Figure 5-22. The widening could also be split on the inside and outside of
the curves equally, as shown in Figure 5-23, or unequally, as shown in Figure 5-24. For
final design, an investigation considering local conditions and dredging costs is required
to optimize bend geometry. If widening the channel cannot be achieved due to existing
soil conditions or structures, tugs must be used to assist ships.
5-6.2.2.3
Entrance Channels.
Entrance Channel Widths
Breakwater gaps. In practice, vessels transit gaps between
breakwaters one at a time. Observations reveal that in practice a
second vessel will normally stand off and allow the first vessel to
complete its passage through the gap to and from protected water. A
minimum entrance gap width of 0.8 to 1.0 times the length of the
vessel appears to be adequate for most sea conditions.
Channel entrances. Vessels require more room to maneuver in and
out of channels leading to protected harbor waters. Therefore,
prescribed widths for interior channels must be increased to allow for
additional channel width at the entrance. By utilizing vessel beam and
its length, the increase in vessel beam can be approximated by the
following equation:
B' = B + lv tan θ
(5-8)
where:
B' = adjusted vessel beam
B = vessel beam
lv = vessel length
θ = yaw angle
Yaw angle should be assumed to range from 5 to 15 degrees, depending
upon entrance exposure. The adjusted vessel width, B', is used in ship lane width
determinations with ratio factors similar to those used in interior-channel design (see
Figure 5-17).
5-50
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