Kentledge Design Spreadsheet

PROJECT: MICROSOFT - 1200mm dia. WTP (WL 715T)

Sheet No: 1Date: 08-04-23

GROUND ENGINEERING PTE LTDDesigned by: Utaya KumarChecked by: Jeffrey Yu

Bearing capacity check on Top SoilBH = 15 Test Pile diameter: 1200 mm

Length of Supporting Kentledge Leg on Each Side = 12 m Working Load = 715 ton Plus 10 % ; Test to 2 timesWidth of Supporting Kentledge Leg on Each Side = 4.5 m Total test load = 15730 kNHeight of Supporting Kentledge Leg on Each Side H₁ = 2.25 m Use 20 nos of Secondary Beam & 2 nos of Main BeamLength of Steel Plate in Contact with Ground on Each Side = 12 mWidth of Steel Plate in Contact with Ground on Each Side B₂ = 4.5 m = 23 kN/m3 for Concrete Kentledge Legs B.S. 648: 1964Area of Direct Bearing on Soil A₁ = 54 m2 A₁ = L₂ x B₂Bearing Pressure on Soil q₁ = 183.61 kN/m2 q₁ =

Estimated Unit Weight of Top Soil (Estimated) = 19 kN/m3 Based on Relevant Borehole from SI ReportEstimated cohesion of Top Soil (Estimated) Cu₁ = 9 kN/m2 Estimated Unit Weight, Cohesion and Friction of SoilEstimated Internal Friction of Top Soil (Estimated) f = 0 ⁰Bearing Capacity Factor Nc₁ = 5.7Bearing Capacity Factor = 1Bearing Capacity Factor = 0Ultimate Bearing Capacity = 55.148 kN/m2 = Terzaghi's EquationGeotechnical Factor of Safety Provided F.O.S. = 0.30 <1.5 NOT OK! F.O.S. = qu/q₁

Bearing Capacity Check on Underlying Soft Soil

Depth of Soft Soil from Ground Level (Estimated) Ds = 4.5 mDepth of Water Table from Ground Level (Estimated) Dw = 2.2 mLength of Spread of Load onto Soft Soil on Each Side = 16.5 m = L₂ + DsWidth of Spread of Load onto Soft Soil on Each Side B₃ = 9 m B₃ = B₂ + DsArea of Spread of Load Bearing on Underlying Soft Soil A₂ = 148.5 m2 A₂ = L₃ x B₃Bearing Pressure on Underlying Soft Soil q₂ = 66.768 kN/m2 q₂ =

Estimated Unit Weight of Soft Soil (Estimated) = 19 kN/m3 Based on Relevant Borehole from SI reportEstimated Cohesion of Soft Soil (Estimated) Cu₂ = 11 kN/m2Estimated Internal Friction Angle of Soft Soil = 0 ⁰Effective Surcharge at Underlying Soft Soil Level = 62.94 kN/m2 =Bearing Capacity Factor Nc₂ = 5.7Bearing Capacity Factor = 1Bearing Capacity Factor = 0Ultimate Bearing Capacity qu₂ = 132.48 kN/m2 qu₂ = Terzaghi's EquationGeotechnical Factor of Safety Provided F.O.S. = 1.98 > 1.5 OK! F.O.S. = qu₂/q₂

L₁B₁

L₂Note: gc

{ [( 1+%add)xN] + (S.W.₁ x nc x LT)+(B₁ x H₁ x L₁ x gc)}/(2 x A₁)

g₁

Nq₁Ng₁qu₁ qu₁ Cu₁Nc₁ x (1+ 0.2B₂/L₂)+q₀Nq₁ + 0.4B₂g₁Ng₁

L₃ L₃

{ [( 1+%add)xN] + (S.W.₁ x nc x LT)+(B₁ x H₁ x L₁ x gc)}/(2 x A₂)

g₂

f₂q₀₂ q₀₂ (g₁ x Dw)+ (g₁ -gw)x (Ds-Dw)

Nq₂Ng₂

Cu₂Nc₂ x (1+ 0.2B₃/L₃)+q₀₂Nq₂ + 0.4B₃g₂Ng₂

Note: Stiffeners were Ignored in Web Buckling & Crushing Check as Design is Governed by Bending Therefore, provide casing as shown in Figure 1.




Therefore, Provide casing as shown below:

Total Load = 19,830.11 kNLoading per kentledge leg = 9,915.06 kN

Geotechnical capacity provided by casings ( Acting as single pile):

(I) Kentledge Left Leg

Dia(m) Meter SPT Skin Friction (kN) Point Bearing - on completely weathered granite (kN) Totalα πD L α x πD x Cū x L A (π r²) Aq'

0.8

0 to 2.0 4 1 2.51328 172 2 864.57 0.502656 172 1548 778.1114882.0 to 5.0 5 1 2.51328 172 3 1296.85

Total 5 2161.42 778.111488 2,939.53

0.8

0 to 2.0 4 1 2.51328 172 2 864.57 0.502656 172 1548 778.1114882.0 to 5.0 5 1 2.51328 172 3 1296.85

Total 5 2161.42 778.111488 2,939.53

0.8

0 to 2.0 4 1 2.51328 172 2 864.57 0.502656 172 1548 778.1114882.0 to 5.0 5 1 2.51328 172 3 1296.85

Total 5 2161.42 778.111488 2,939.53

0.8

0 to 2.0 4 1 2.51328 172 2 864.57 0.502656 172 1548 778.1114882.0 to 5.0 5 1 2.51328 172 3 1296.85

Total 5 2161.42 778.111488 2,939.53

Total 11,758.13qu = ∑[πD(Cū)L] + [π(r²)q'N]

= 11,758.13 kN > 9,915.06 kN OK!

Cū Cū 9Cū (kN/m²)




(II) Kentledge Right Leg

Dia(m) Meter SPT Skin Friction (kN) Point Bearing - on completely weathered granite (kN) Totalα πD L α x πD x Cū x L A (π r²) Aq'

0.8

0 to 2.0 4 1 2.51328 172 2 864.57 0.502656 172 1548 778.1114882.0 to 5.0 5 1 2.51328 172 3 1296.85

Total 5 2161.42 778.111488 2,939.53

0.8

0 to 2.0 4 1 2.51328 172 2 864.57 0.502656 172 1548 778.1114882.0 to 5.0 5 1 2.51328 172 3 1296.85

Total 5 2161.42 778.111488 2,939.53

0.8

0 to 2.0 4 1 2.51328 172 2 864.57 0.502656 172 1548 778.1114882.0 to 5.0 5 1 2.51328 172 3 1296.85

Total 5 2161.42 778.111488 2,939.53

0.8

0 to 2.0 4 1 2.51328 172 2 864.57 0.502656 172 1548 778.1114882.0 to 5.0 5 1 2.51328 172 3 1296.85

Total 5 2161.42 778.111488 2,939.53

Total 11,758.13qu = ∑[πD(Cū)L] + [π(r²)q'N]

= 11,758.13 kN > 9,915.06 kN OK!

Cū Cū 9Cū (kN/m²)




** Each kentledge leg requires 4 numbers of 800mm diameter and depth of steel casing.Total 8 numbers steel casings are required for temporary setting up of kendledge. Refer to Figure below.

12 mDia 1200 mm

Working Test Pile

Dia 800mm5.0 m

Dia 800mm5.0 m

Dia 800mm5.0 m

Dia 800mm5.0 m

4.5m

2.25m

2.0 m

1.6m

1.6m

1.6m

2.0 m

2.25m

2.0 m

2.0 m

1.6m

1.6m

1.6m

12 m

Dia 800mm5.0 m

Dia 800mm5.0 m

Dia 800mm5.0 m

Dia 800mm5.0 m

4.5m

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Kentledge Design Spreadsheet