CROSS SECTIONAL DETAILS OF BREAKWATER

DESIGN OF BREAKWATER

Available data:

Design Water depth = 4.0m + 0.8m (Mean water + Tidal correction)

Maximum wave height, Hmax = 0.78 x 4.8

= 3.744m

Significant wave height Hs for the calculation of Armour weight, Hs =

=

= 2.34m

6.1

maxH

6.1

74.3

DESIGN OF ARMOUR LAYER

Assuming armour unit is rough quarry stone, 2 layers, no overtopping,

According to Hudson.

W =

Where,W = Wt. Of individual armour unit in ton.H = Design wave height in metersKD = Stability co-efficient = 2θ = Angle of structure slop measured with

horizontalKr = Specific gravity of armour unit relative to

the water at the structureWr = Unit weight of armour in 2.65t/m3Ww = Unit weight of sea water 1.025t/m3

cot)1( 3

3

rD

r

sk

HW

DESIGN OF ARMOUR LAYER

Sr = =2.585

Cot θ = 1.5

W = = 2.84T

Provide boulder stone of 3.0T.

Nominal diameter (D) of stones corresponding to the Armour ruble stone weight

D = = = 1.04

w

r

W

W

5.1)1585.2(2

34.226503

3

x

x

3

1

rW

W 3

1

2650

3000

ARMOUR THICKNESS

The thickness of the armour layer(T) can be calculated as

T = nKdD

Kd = Layer coefficient = 1.15

T = 2 x 1.15 x 1.04

= 2.392m

Adopt 2.5m thick armour layer

CREST WIDTH

The crest width depends on the maximum of the following

Minimum number of stones required

Width depends on the degree of over topping

The functional aspect during the construction and afteruse which may be equal to the width of the wheel.

CREST WIDTH

B =

WhereB = Crest width in mN = number of quarry stone (n=2)Kd = Layer co-efficientW = Mass of Armour unit.Wr = Mass density of Armour unit Kg/m3

B = = 2.392m

Provide a crest width of 4.0m

3

1

r

dW

WnK

3

1

2650

300015.12

x

CORE LAYERThe core layer supports the protective armour cover and any

other under layer.

It prevents sediments passing thought the breakwater.

The size of stone in core would be w/100, however for thepractical limitations as well as to serve the purpose of the coreand to avoid silt passing a wider range is suggested.

Provide stones of weight 50kg to 125kg.

BEDDING LAYERBedding layer act as foundation to support the entire structure.

The stones of 1Kg to 50Kg can be provided as bedding layer to athickness of 150mm.

TOE MOUND (GABBION BOX)

Toe mound width should be maximum of 2x(WaveHeight) or 0.4x(water depth)

2x(wave height) = 2(2.34) = 4.68m

0.4x(water depth) = 0.4(4.8) = 1.92m

Width of toe mound = 5.0m

Height of toe mound = 2.5m

Note: A toe mound is to be placed on side of the break water for preventing the sliding of thestones and protecting the slope failure. A toe mound of 5.0m top width and 2.5m heightis provided. Toe mound is provided with stones of size 150mm.

BREAKWATER CROSS SECTION

DESIGN OF SEAWALL

Available data:

Design Water depth = 2.0m (Considering the tsunami runupof 1.8m above MSL as per the data given by Tuticorin Port)

Maximum wave height, Hmax = 0.78 x 2.0

= 1.56m

Significant wave height Hs for the calculation of Armour weight, Hs =

=

= 0.975m

6.1

maxH

6.1

56.1

DESIGN OF ARMOUR LAYER

Assuming armour unit is rough quarry stone, 2 layers, no overtopping,

According to Hudson.

W =

Where,W = Wt. Of individual armour unit in Newton.H = Design wave height in metersKD = Stability co-efficient = 2θ = Angle of structure slop measured with

horizontalKr = Specific gravity of armour unit relative to

the water at the structureWr = Unit weight of armour in 2.65t/m3Ww = Unit weight of sea water 1.025t/m3

cot)1( 3

3

rD

r

sk

HW

DESIGN OF ARMOUR LAYER

Sr = =2.585

Cot θ = 4

W = = 0.08T

Provide 400kg to 500kg weight armour in two layers considering tsunami effect.

Nominal diameter (D) of stones corresponding to the Armour ruble stone weight

D = = = 0.426

w

r

W

W

4)1585.2(2

975.026503

3

x

x

3

1

rW

W 3

1

2650

5.206

ARMOUR THICKNESS

The thickness of the armour layer(T) can be calculated as

T = nKdD

Kd = Layer coefficient = 1.15

T = 2 x 1.15 x 0.426

= 0.98m

Adopt 1.25m thick armour layer

CREST WIDTH

The crest width depends on the maximum of the following

Minimum number of stones required

Width depends on the degree of over topping

The functional aspect during the construction and afteruse which may be equal to the width of the wheel.

CREST WIDTH

B =

WhereB = Crest width in mN = number of quarry stone (n=2)Kd = Layer co-efficientW = Mass of Armour unit.Wr = Mass density of Armour unit Kg/m3

B = = 0.98m

Provide a crest width of 1.5m

3

1

r

dW

WnK

3

1

2650

5.20615.12

x

CORE LAYERThe core layer supports the protective armour cover and any

other under layer.

It prevents sediments passing thought the breakwater.

The size of stone in core would be w/100, however for thepractical limitations as well as to serve the purpose of the coreand to avoid silt passing a wider range is suggested.

Provide stones of weight 50kg to 125kg.

BEDDING LAYERBedding layer act as foundation to support the entire structure.

The stones of 1Kg to 50Kg can be provided as bedding layer to athickness of 150mm.

TOE MOUND (GABBION BOX)

Toe mound width should be maximum of 2x(Wave Height) or 0.4x(water depth)

2x(Height of breakwater) = 2(0.975) = 1.95m

0.4x(water depth) = 0.4(2.0)= 0.8m

Width of toe mound = 2.5m

Height of toe mound= 1.5m

Note: A toe mound is to be placed on side of the break water for preventing the sliding of thestones and protecting the slope failure. A toe mound of 2.5m top width and 1.5m height isprovided. Toe mound is provided with stones of size 150mm.

SEAWALL CROSS SECTION