waterway engineeringwaterway engineering chapter 7

1、Chapter 7Channel alignment 7.1 general 7.2 variable alignment 7.3 straight alignment 7.4 PINAC method7.1 general To minimize initial and maintenance dredging, the alignment of a navigation channel is usually designed to follow the course of the deeper channel in a river or estuary.7.2 variable align

2、ment The strength of the hydraulic forces in the estuary will usually dictate channel alignment. An example is Grays Harbor, Washington, which has high tides and a large tide prism, as shown in Figure 7-1.FJ ,G U R E7-1.Variable A li妇 unen t Ship Channels (Adap .ted frorn ASCE枷nual 入T.o 80).乏J-3王Nt1

3、30出ORTHO V山几从2 川扣已i ”2 一”巨乃 G,R,AYSHARBOR WASHINGTON10-勹S 10雹烂矗土凰I 阿 腻 心 畔 T 印 IiiNotes:Mean tide rang.e 9.00 feet Maximum Ude ran1g e1 7 _5 feet ship channel 26 m五l e s l o n g7.2 variable alignment These systems may have channels that migrate, such as Grays Harbor, where the channel has migrated t

4、o a position adjacent to the South Jetty (Figure 7-2). f. .一 ,.”“千今Tha1何egF I GURE 7-2. Grays Harbor C 加 nnel Mig,ation (Cotn mift ee on Tidal Hydraulics, C01rs of Engineers, 1 9 95 ) .7.3 straight alignment Straight ship channels are possible when the hydraulic dynamics of the system are small. Fig

5、ure 7-3 shows an example of a straight ship-channel project in Mobile, Alabama.儿 王CQIBA I.,叩 1片仑凸,1i_N1_lr一心 ；守泗 孕恋初 L 丘五 0寂冗1 心皿FT- -|7.4 PINAC method “Channel alignment should be assessed with regard to: the shortest channel length; conditions/basins, and so on, at either end of the channel; the need to avoid obstacles or areas of accretion, which are difficult or expensive to remove or require excessive (and, hence, costly) maintenance dredging; prevailing winds, currents, and waves; avoiding bends close to port entrances; the edge of