EM 1110-2-1100 (Part V)
31 Jul 2003
EXAMPLE PROBLEM V-4-9
FIND:
The approximate time required for 50 percent of the placed beach fill volume to be lost from the
placement area due to alongshore spreading and a background shoreline recession rate of 0.5 m/year.
GIVEN:
Assume the planform of the beach fill is initially rectangular with an alongshore length of 6 km
and an estimated offshore width of 50 m (after equilibration).
hb = Hb/0.78
n = 0.4
Assume:
K = 0.77
g = 9.81 m/s2
Hb = 0.95 m
db = 1.5 m
Cgb = (g hb)
ρs/ρ = 2.65
dc = 6.0 m
SOLUTION:
Equation III-2-26 gives ε = 0.03568 m2/sec (see EXAMPLE PROBLEM V-4-7)
Equation V-4-15 gives
2
2
E
0.5
' 0.0001 years &2
l'
'
∆yo
50
2E(p&1) ε
(2) (0.5) (.5&1)
0.03568
(31.536 X10 6) ' &0.04980 years &1
m'
&
'
&
∆yo
50
πa 2
(3.14)(3000)2
n ' (1&p) ' (1&.5)2 ' 0.2500
and
&m & m 2 & 4 l n
0.04980 & (0.04980)2 & (4)(0.0001)(0.2500)
5.07 years
t50%
'
'
2l
(2)(0.0001)
V-4-54
Beach Fill Design
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