CW Pipe Thrust Block 1

KORBA WEST THERMAL POWER PROJECT - 1 x 500 MW (EXTENSION – STAGE III)

DESIGN CALCULATION FOR THRUST BLOCK (CW PIPES) 0802-FCE-DO-C0132

ANNEX B‐1.0 DESIGN OF CW PIPES THRUST BLOCK TYPE ‐ 1

Calculation of Total Anchor forces:

(For Anchor forces, Refer BHEL drg PE‐DG‐312‐611‐C028 ‐ PHB (A‐B BAY) GA OF COOLING WATER PIT)

X Y Z Fx Fy Fz Mx My Mz Mxi Myi Mzi(m) (m) (m) kN kN kN kNm kNm kNm kNm kNm kNm

1 A1 0.000 0.000 ‐8.270 210.00 ‐240.00 60.00 165.00 65.00 439.00 2149.80 1801.70 439.00

2 A2 0.000 0.000 ‐2.760 196.00 ‐100.00 8.00 43.00 130.00 45.00 319.00 670.96 45.00

3 A3 0.000 0.000 1.720 194.00 ‐100.00 2.00 13.00 32.00 45.00 ‐159.00 ‐301.68 45.00

4 A4 0.000 0.000 7.230 200.00 ‐240.00 ‐56.00 ‐162.00 ‐42.00 439.00 ‐1897.20 ‐1488.00 439.00

5 Rail load 1225.00 1225.00

800.00 ‐680.00 14.00 412.60 682.98 2193.00

Size of Thrust block: 2.500 2.500

Length of thrust block = 19.46 m

Width of thrust block = 5.00 m 1.460 m

Depth of thrust block = 4.20 m 9.730

Gross volume of concrete = 19.46 x 5 x 4.2 19.460 m 5.510 m

5.000 m

TOTAL FORCES

Sl.No

Moments about C.G. of Thrust BlockDistance from C.G. of Thrust Block Forces at AnchorsAnchor points

CG of Thrust block

Anchor Points

A2

A1

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= 408.66 m3

Deduction for Pipe penetration: 4.480 m

Type‐1 Type‐2

Dia of pipe = 2.2 m 3.2 m 5.510 m

Area of pipe = PI() x 2.2^2 / 4 PI() x 3.2^2 / 4 9.730

= 3.8 m2 8.04 m2

Length of pipe (appx.) = 10 m 10 m

Volume occupied by pipe = 3.8 x 10 8.04 x 10 2.500 m

= 38 m3 80.40 m3

X (+)

Z(+)

CG of Thrust block

CG of Thrust block

Anchor Points

THRUST BLOCK (PLAN)

Y(+)Upwards

A2

A3

A1

A4


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Note:

Rail track load is not considered for check against sliding, because additional rail track load will counter the Pipe sliding forces, hence it is not considered.

Moment induced due to eccentric rail track load is considered for check against onerturning, because this adiitonal moment is additive to the pipe moments.

Rail track load is considerd for check against bearing pressure, because this additional load is additive to the pipe forces.

Additional wheel loads due to Rail track loads transporting the Stator equipment.

A maximum of 10 axles ‐ each axle spaced at 2.0m, shall pass in the total length (20.5m) of the thrust block at any given period of time.

Assuming 25 Tonne per axle, total load acting over the thrust block

250 x 10 = 2500 kN

Additional Moment due to eccentric rail track load wrt the CG of thrust block

Eccentricity of rail track loadf from the CG of the thrust block = 0.49 m

Moment induced due to eccentric rail track load = 2500 x 0.49

= 1225 kNm

Design Data:

Unit weight of water = 10 kN/m3

Unit weight of soil = 18 kN/m3

Unit weight od submerged soil = 8 kN/m3

Unit weight of RCC = 25 kN/m3

Coefficient of friction = 0.5


Total volume of concrete excluding pipe = 408.66 ‐ (38 + 80.4)

= 290.26 m3

Weight of concrete (submerged) excluding pipe = 290.26 x (25 ‐ 10)

= 4353.90 kN

Weight of water in pipe = (38 + 80.4) x 10

= 1184.00 kN

Total weight of thrust block = 4353.9 + 1184

= 5537.90 kN


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Check for Sliding in X‐direction:

Maximum lateral force in = 800.0 kN

X‐direction

Maximum possible friction = m*W

= 0.3 x 5537.9

= 1661.37 kN

Factor of safety against = 1661.37 / 800

sliding in x direction

= 2.1 > 1.5

HENCE SAFE

Check for Sliding in Z‐direction:

Maximum lateral force in = 14 kN

Z‐direction

Maximum possible friction = m*W

= 1661.37 kN



sliding in z direction

= 118.7 > 1.5

HENCE SAFE


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Check for Twisting moment:

Passive resisting force = gs kp.H2/2 kN

Passive resisting moment = (Fp/2) x (Lb/2) x (2/3 x Lb/2) x 2

Passive resisting moment = Fp x Lb2 / 6 kNm

Fp = gs x kp x H2/2

Angle of repose = 30 degree

Kp = 3

Density of soil gs (bouyant dens = 10 kN/m3

H = 4.2 m

Lb = 19.46 m

Resisting LA = 4.865 m

Fp = 10 x 3 x 4.2^2 / 2

= 264.6 kN/m

Passive resisting moment = 264.6 x 9.73 x 4.865

= 12525.22 kNm

Maximum twisting moment 682 98 kNm


Maximum twisting moment = 682.98 kNm

Factor of safety against = 12525.22/682.98

twisting

= 18.3 > 1.5

HENCE SAFE


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Check for Overturning Moment about X‐axis:

Resisting moment = 5537.9 x 5/2

about X axis = 13844.75 kNm

Overturning Moment Mx = 412.6 kN


Overturning about X direction = 33.6 > 1.5

HENCE SAFE

Check for Overturning Moment about Z‐axis:

Resisting moment = 5537.9 x 19.46/2

about Z axis = 53883.77 kNm

Overturning Moment Mz = 2193


overturning in z direction = 24.6 > 1.5

HENCE SAFE

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Calculation of Base pressure:

Weight of Concrete = 290.26 x 25

(excluding pipe) = 7256.5 kN

Weight of water = 1184.00 kN

Total vertical load, P = 680 + 7256.5 + 1184 = 9120.50 kN

Total vertical load acting over the trust block, = 9120.50 + 2500 = 11620.50 kN

including rail track load

Total moment about X‐axis, Mx = 412.6 kNm

Total moment about Z‐axis, Mz = 2193 kNm

Maximum Base pressure = P/A + Mx / Zx + Mz / Zz

Base area, A = 19.46 x 5

= 97.30 m2

Zx 19 46 x (5 x 5) / 6


Zx = 19.46 x (5 x 5) / 6

= 81.08 m3

Zz = 5 x (19.46 x 19.46) / 6

= 315.58 m3

Maximum Base pressure, qmax = P / A + Mx / Zx + Mz / Zz

= (9120.5/97.3)+(413/81.08)+(2193/315.58)

= 131.47 kN/m2

Additional load from RCC foundation laid to support the rail track


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700mm thk concrete is provided as support for the rail track. Load from this concrete portion on the thrust block (Ref drg no: PE‐DG‐312‐622‐C001)

0.7 x 25 = 17.5 kN/m2 Hence take 20 kN/m2 conservatively

Total base pressure = 131.47 + 20

= 151.47 kN/m2

Allowable net SBC = 130 kN/m2

Gross SBC = 130+ (18 x (4.2 + 0.78)

= 206.38 kN/m2

Check for Bearing Pressure = 151.47 kN/m2 < 206.38 kN/m2

HENCE SAFE

Reinforcement details:

Provide 12 mm diameter bars @ 200 mm c/c at 75 mm distance from the surface all around the thrust block.

Also provide 12mm dia. bars @ 600mm c/c for inner mesh reinforcement of thrust block.


Summary of Stability Checks:

FOS Allowable Check

Sliding in X‐axis 2.1 > 1.5 Safe

Sliding in Z‐axis 118.7 > 1.5 Safe

Twisting Moment 18.3 > 1.5 Safe

Overturning about X‐axis 33.6 > 1.5 Safe

Overturning about Z‐axis 24.6 > 1.5 Safe

Base pressure 151.5 < 206.38 Safe


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CW Pipe Thrust Block 1