20061804 Ver 23_Buoyancy Resistance Calcs_20180619

Buoyancy Resistance Calculations for SCM
Assumptions:
Unit Weight of Saturated Soil [gsat] = 120 pcf
Unit Weight of Concrete [gconc] = 147 pcf
Unit Weight of Water [g,,] = 62.4 pcf
Base Length [L] = 5 feet
Base Width [W] = 4 feet
Known:
Inside Diameter of Wetwell (ft) =
ID
Outside Diameter of Wetwell (ft) =
OD
Depth of Structure (ft) =
D
Minimum Base Slab Thickness (in) =
T
Minimum Top Slab Thickness (in) =
Tts
Average Invert Thickness (in) =
Ti
Base Slab Area (ft) =
A
Displacement Volume, Wetwell (ft) =
Vw
Displacement Volume, Base Slab (ft) =
Vbs
Buoyant Force =
B
Effective Weight of Soil Over Slab Extension =
S
Structure Weight, Walls =
Ww
Structure Weight, Invert =
Wi
Structure Weight, Top Slab =
Wts
Structure Weight, Base Slab =
Wbs
Structure Weight, Total =
W
Table of Calculations:
A
WW
Wi
Wts
Wbs
W
(ft)
(lbs)
(lbs)
(lbs)
(lbs)
1
(lbs)
19.63
2368.60
445.9094
0.00
1442.438
4256.9446
Same if Extended Moorbase
Same if Extended Moorbase
2.78
3.44
5
6
0
6
2'X3' Box
2'X3' Box
(L x W) or pi(L/2)`
pi(OD/2)2D
A(T/12)
(Vw + Wbs) x gw
(gsat - gw) x (A-pl(OD/2)2)D
(pi(OD/2)2 - pl(ID/2)2)Dgconc
pi(ID/2)2Tigconc
pi(OD/2)2(Tts/12)gconc
A(T/12)gconc
Ww+WI+Wts +Wbs
Vw Vbs B S W+S=l 7233.60
(ft3) (ft3) (lbs) (lbs) B =1 3510.59 FOS
46.45 9.81 3510.59 2976.66 Is W + S > B? YES 2.06
Conclusion:
Since the weight of the structure and the base slab is greater than the buoyancy for of the wetwell,
the resistance to buoyant force is provided.