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Coastal Engineering: Theory and Practice
(ii) Goda
p* = 2.7 m
k = 0.301 m-1 at h3 = 4 m, hc = 2.5 m < r?*, assume hb = hs = 4 m,
hyj — 7 m
/ 2x0.301x4 \2
ai = 0.6 + 0.5 . . .
- ----- -
= 0.7
\smh2 x 0.301 x 4/
4-4 /1.8\2 n
2x4
A a
a2 = mm. of -—- —
= 0 or —— = 4.4
3 x 4 \ 4 /
1.8
02=0
7 — 2.5 /
1
\
a3 = 1 - —— (J - cosh(0 301 x 4) ) = 049
Pi = 0.5(1 + l)(0.7 + 0) x 1 x 1.8 = 1.3 t/m2
P2 = fl - — Pi = fl ~ 14^) 113 = °-09 V™2
\
P* /
\ 4. r /
p3 = 0.49 x 1.3 = 0.6 t/m2
R = |2.5 x (1.3 + 0.09) + |(1.3 + 0.6)(7 - 2.5) = 5.9 t/m.
Horizontal forces estimated from,
Miche-Rundgren is 7.9 t/m.
Goda is 5.9 t/m
i.e., Miche-Rundgren formula estimâtes about 1.3 times that predicted by
the formula of Goda.
Problem VI
Design a rubble mound breakwater in a water depth (d) of 8 m under the
50-year wave climate of 5 m (Fs50) and 8 sec (Tm). Consider, the highest
high water level (HHWL) is 2.4 m with a storm surge of 0.5 m.
Solution
Total water depth {dtotai) in front of the breakwater is estimated as,
dtotai = d + HHWL + Storm surge = 10.9 m.
Hence, maximum sustainable wave height, #max — 0.78 x dtotai = 8-5