EXAMPLE PROBLEM V-4-7

FIND:

The "half-life" of the specified beach fills (time at which 50 percent of the beach-fill material

remains within the placement area).

GIVEN:

Both projects have a rectangular planform and differ only in alongshore length. Beach fill A

has an alongshore length of 3 km, whereas beach fill B has an alongshore length of 6 km. Both projects

are subjected to the same wave environment.

Assume:

SOLUTION:

Equation III-2-26 gives

0.77 (0.95)2.5 9.81/0.78

m2

1

1

1

ε'

.

.

.

' 0.03568

8

(2.65 & 1) (1 & 0.4) (2.5 % 6.0)

sec

Solving Equation V-4-12 for *t *and p(t) = 0.5 gives

'

4ε

Half-life of beach fill A

(1500)2 (3.14)

' 49.526 X 106 sec 1.57 years

'

(4) (0.03568)

Half-life of beach fill B

(3000)2 (3.14)

' 198.102 X 106 sec 6.28 years

'

(4) (0.03568)

Beach Fill Design

V-4-51

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