8. Design of Coastal Structures
279
Filter layer
Following the earlier step, the weights of filter layer stones which distributes
the entire rubble stone structure weight into the sea bed is
to — of the
core layer. Since, the seabed is of stable strata, the similar range of stones
is considered, i.e., the range of stone weights in the filter layer is
to
i. Hence, adopt the range of filter layer stones of 6 kg to 22 kg subject
to the minimum size of filter stones as 10 mm. The filter layer thickness is
adopted as 300 mm.
Toe layer
W
W
The range of stone weights in the toe layer is —• to —, i.e., 2.2 ton to
lu
lo
1.5 ton similar to underlayer stones. In a typical design, the under layer is
extended to form a toe. Minimum width of toe is three layer thickness and
the minimum toe height is two layer thickness. Thus, the width is arrived
at 2.85 m, say 3 m and the height (thickness) of toe layer is 1.9 m, say 2 m.
Crest élévation
Crest Elévation is calculated as (dtotai+ Run-up + Free board).
For wave run up (CEM, 2006), the surf similarity parameter, £ is
calculated.
tan a
~
ZirH
2tt x 7 „
s-=^=^=0'07005
£ = , 1//2
= 1.8896
VO.07005
From CEM (2006), — = 1.0, R = 7 m
Hence, fix, say crest élévation at 28 m from seabed with a free board
of 0.5 m. Further, the minimum crest width required is three armour layer
unit thickness. Here, provide 7.2 m wide crest. Hence, provide armour layer
with tetrapod units and, underlayer, toe berm and core with quarry stones.
Problem VIII
Design a non-overtopping concrète caisson breakwater of rectangular section in a water depth (d) of 8 m. The high tidal level is 2.5 m and the
design wave height is 4 m. The horizontal wave force exerted on the caisson
279
Filter layer
Following the earlier step, the weights of filter layer stones which distributes
the entire rubble stone structure weight into the sea bed is
to — of the
core layer. Since, the seabed is of stable strata, the similar range of stones
is considered, i.e., the range of stone weights in the filter layer is
to
i. Hence, adopt the range of filter layer stones of 6 kg to 22 kg subject
to the minimum size of filter stones as 10 mm. The filter layer thickness is
adopted as 300 mm.
Toe layer
W
W
The range of stone weights in the toe layer is —• to —, i.e., 2.2 ton to
lu
lo
1.5 ton similar to underlayer stones. In a typical design, the under layer is
extended to form a toe. Minimum width of toe is three layer thickness and
the minimum toe height is two layer thickness. Thus, the width is arrived
at 2.85 m, say 3 m and the height (thickness) of toe layer is 1.9 m, say 2 m.
Crest élévation
Crest Elévation is calculated as (dtotai+ Run-up + Free board).
For wave run up (CEM, 2006), the surf similarity parameter, £ is
calculated.
tan a
~
ZirH
2tt x 7 „
s-=^=^=0'07005
£ = , 1//2
= 1.8896
VO.07005
From CEM (2006), — = 1.0, R = 7 m
Hence, fix, say crest élévation at 28 m from seabed with a free board
of 0.5 m. Further, the minimum crest width required is three armour layer
unit thickness. Here, provide 7.2 m wide crest. Hence, provide armour layer
with tetrapod units and, underlayer, toe berm and core with quarry stones.
Problem VIII
Design a non-overtopping concrète caisson breakwater of rectangular section in a water depth (d) of 8 m. The high tidal level is 2.5 m and the
design wave height is 4 m. The horizontal wave force exerted on the caisson