Caisson Study

7/28/2019 Caisson Study

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Sl. No. Parameter Unit Value

1 Inside Dia, Din m 21.984

2 Outside Dia, Dout m 25.016

3 Total Height, H m 16

4 Sea Water density, ρseawater kg/m3 1020

5 Concrete Mass T 230.39953

6 Caisson Mass T 319.7

7 Outer Shell Mass T 74.4027878 Inner Shell Mass T 65.384989

9 Top Shell Mass T 29.082189

10 Total Mass of Caisson T 718.96949

11

Height of water column inside Caisson,

Hsubmerged m 6.6885639

12 Height of Caisson above sea level, Htop m 9.3114361

13 Height of Caisson base from sea bed m 3.6514361

14

Height of water column inside annular

region, x m 5.791073

15

Corresponding submersion of Caisson,

y m 3.6514361

3. Caisson Condition after Height raising, Ballast Valve Closed full an

Caisson Floating and Sinking Study

1. Caisson Condition during Floating (Water inside inner sheel and an

2. Caisson Condition during Grounding (Ballast Valve opened and An



Remarks

As per drawing As per drawing

Concrete build-up of 1m height at the inside triangular annular base of Caisson was

done to enable floating.

As per available drawings

Applying archmedies principle: Weight of water Volume displaced by Caisson =

Buoyancy Force = Wt. of caisson

To ground the caisson

Let us assume that, if Caisson has to be sunk for y m, the water should be filled inannular space to x m. Applying the same principle, Additional weight of water in

annular space = Addittional Weight of volume of water displaced

This desired level had to be such that the Caisson legs should have touched the

ground. But, as the ballast valve opened hurriedly and the dewatering pump

failed, the annular space fiiling was uncontrolled and it filled full.

f f C

annular space dewatered full as planned for lifting

nular space empty)

ular Space started filling)



Caisson During Floating

Triangular

Height, Htri,

2380 mm

1500m

m

D, out = 25

D, in

α

H, concrete,

1000mm

T o t a l H e i g h t , H ,1 6 0 0 0

m m

C y l i n d r i c a l

H e i g h t , H c y l ,1 3 6 2 0

m m

H , s u b m e r g e d

, 6 . 8 8 m

H , c o n e

H , c o n e2

H , c o n e 3

D, c

D, co



Water

Sand

No Fill Empty

Sea Water

Sand

Concrete

Caisson After Sinking in wrong Position

1500mm

D, out = 25016 mm

D, in = 21984 mm

1360mm

1 6 0 0 0 m m

1 3 6 2 0 m m

Bed

H , s e a b e d ,1 0 . 3 4 m

H , u n d e r b e d , 4 . 6 6 m

sea

Triangular

Height, Htri,

2380 mm



Sl. No. Parameter Unit Value Remarks

1 Wind Speed in KMPH km/hr 40 Assumed

2 Wind Speed in m/sec, Vair m/sec 11.111111

3 Air Density, ρair kg/m3 1

4 Equivalent Pressure, Peq N/m2 61.728395 1/2 * ρair * Vair

2

5 Accln due to gravity, g m/sec2 9.81

6 Outer Dia, Dout m 25.016

7 Eposed Height, Hexp m 9.3114361 H - Hsubmerged

8Total Surface Area equivalent to

exposed heightm

2 731.41554 2 * π * Dout/2 * Hexp

9 Exposed surface area, Aexp m2 365.70777 1/2 * 2 * π * Dout/2 * Hexp

10 Equivalent Force, Feq N 22574.554 Peq * Aexp

11 Force converted to mass, Fdrag air T 2.3011778 Feq / g

12 Water Speed in KMPH km/hr 3 Assumed

13 Water Speed in m/sec, Vwind m/sec 0.8333333

14 Water Density, ρweter kg/m3 1020

15 Equivalent Pressure, Peq N/m2 354.16667 1/2 * ρwater * Vwater

2

16 Eposed Height, Hexp m 6.6885639 Hsubmerged

17Total Surface Area equivalent to

exposed heightm

2 525.3883 2 * π * Dout/2 * Hexp

18 Exposed surface area, Aexp

m

2 262.69415 1/2 * 2 * π * Dout/2 * Hexp

19 Equivalent Force N 93037.511 Peq * Aexp

20 Force converted to mass, Fdrag water T 9.4839461 Feq / g

21 Total Force T 11.785124 Fdrag air + F drag water

Drag due to Wind

Drag due to Water

Drag Force Calculation



Gravitational Force,F(g) =M(total) * g

Buoyancy Force, F(B)=V(displaced) * ρ(seawater) *g

Bollard Pull Force, F(P)=P(Engine) / v(Caisson) Drag Force, F(D)

=F(Drag, water) + F (Drag, Air)




1 Vdisplaced m3

704.87205

2Mean Sea Level from Sea Bed,

Hseam 10.34

3 Caisson Base from mean sea bed m 3.6514361

4

Additional Water Required to be

displaced for Caisson Grounding,Vadditional

m3

488.74341

5

Annular and Central Space Water

Colum Height to Ground Caisson,

Hground caisson

m 5.791073

(Vannular cylinder / m + Vcentral / m)* (Hsea - Hsubmerged)

Htriangular + [{Vadditional - (Vfull triangle - Vfilled triangle)} / (Vannular

cylinder / m + V central / m)]

Remarks

Caisson Sinking Calculation

(Vannular cylinder / m + Vcentral / m)* (Hsubmerged - Htriangular ) +

Vfull traingle

Hsea - Hsubmerged




1

Additional Mass of the Raising

material, Madditional T 71.794965

2Composite Mass After Height

Raising, MfinalT 790.76446

3 Buoyancy Force Required T 790.76446

4Water Height available for

Buoyancy forcem 10.34

5 Buoyancy Force available T 1411.6854

6 Additional Buoyancy Force

AvailableT 620.92093

Equal to Mean Sea Water Height Available

ρseawater * Hsea * (Vannular cylinder / m + V central / m)If this additional force is capable enough to overcome

the frictional forces offered by sea bed on Caisson, it

shall float again.

Remarks

Caisson Refloating Calculation

(Hadditional / H) * (Mcaisson + Mouter shell + Minner shell)

Mtotal + Madditional

.




1 Din m 21.984

2 Dout m 25.0163 Annular Width, W m 1.5

4 Total Height, H m 16

5Triangular Scetion Height,

Htriangular m 2.38

6 Cylindrical Height, Hcyl m 13.62

7 Vinner cylinder m3 5167.2586

8 Vouter cylinder m3 6690.8686

9Height of concrete fill,Hconcrete

m 1.360567

10 Half Angle, Tan α 0.6302521

11 Hcone m 19.846027

12 Hcone2 m 18.846027

13 Dcone2 m 23.301

14 Vcone m3 3249.808

15 Vcone2 m

3 2677.425

16 Vtruncated cone m3 572.38307

17 Vconcrete cylinder m3 668.38288

18 Vfilled triangle m3 95.999802

19Density of Concrete,

ρconcrete

T/m3 2.4

20Mass of Concrete,

MconcreteT 230.39953

21 Hcone3 m 17.466027

22 Dcone3 m 21.984

23 Vcone3 m3 2208.7978

24 Vfull traingle m3 128.17233

25 Vannular cylinder m3 1523.61

26 Vannular cylinder / m m3 111.86564

Outer Shell Thickness

Remarks

As per Drawing

As per Drawing As per Drawing

Submerged Height Calculation

As per Drawing

πDin2/4* Hcyl

πDout2/4* Hcyl

Htriangular /W

Dout/2Tanα

Hcone - Hconcrete

Dout - (2* Hcone2 * Tanα)

1/3* π * Dout2/4 * H

1/3* π * Dcone2

2/4 * H

cone2Vcone - Vcone2

π * Dout2/4 * Hconcrete

Vconcrete cylinder - Vtruncated cone

Assumed

Vfilled triangle * ρconcrete

Hcone - Htriangular

Din

1/3* π * Dcone32/4 * Hcone3

π * Dout2/4 * Htriangular - (Vcone - Vcone3)

Vouter cylinder - Vinner cylinder

Vannular cylinder / Hcyl



35 Total Caisson Mass, Mtotal T 718.96949

36Central Section Arc

Length, Larcm 1

37Height of Central Scetion

Empty Arc, Harcm 13.62

38Volume of Central Section

/ m, Vcentral / mm

3 21.984

39Volume of Central Section

Arc Length, Vcentralm

3 299.42208

40 Hsubmerged m 6.6885639

41 Vdisplaced m3 704.87205

Larc * Din * Hcylinder (Approximating the section to rectangular)

Applying Archemedes Principle, Wt of water displaced = Total

Wt. of Caisson. This gives, [{(Hsubmerged - Htriangular ) * (Vannular

cylinder / m +Vcentral / m)}+ Vfull triangle] * ρseawater = Mtotal This gives,

Hsubmerged = [{(Mtotal / ρseawater )- Vfull triangle} / (Vannular cylinder / m +

Vcentral / m)]+ Htriangular

(Vannular cylinder / m + Vcentral / m)* (Hsubmerged - Htriangular ) + Vfull traingle

Mconcrete + Mcaisson + Mshellout + Mshellin + Mshelltop

Hcylinder

Larc * Din (Approximating the section to rectangular)



No Fill Empty

Sea Water

Caisson During Floating

Triangular

Height, Htri,

2380 mm

1500mm

D, out = 25016 mm

D, in = 21984 mm

α

H, concrete,

1360mm

T

o t a l H e i g h t , H ,1 6 0 0 0 m m

C y l i n d r i c a l H e i g h t , H

c y l ,1 3 6 2 0 m m

H , s u b m e r g e d , 6 . 7 m

H , a b o

v e ,

3 . 6 5 m

H , c o n e

H , c o n e2

H , c o n e 3

D, cone2

D, cone3



Empty

No Fill Sea Water

1m

Caisson Study

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