Project :

Client :
Title: Pile Capacity (Compression )
Pile Details:
Existing Bed level = 0.0 m
Design Water Level = 0.0 m Safe Vertical Capacity of pile = 190 kN
Pile Diameter, D = 0.30 m Safe Uplift Capacity of pile = 143 kN
Pile Cut-off level from EGL = 1.0 m
Pile Cut-off Level = 1.0 m
Pile Founding level = 16.0 m
Total Length of Pile from EGL = 16.0 m
Pile Embedment length = 15.0 m
Pile Density = 25.0 kN/m3
Factor of Safety = 3
Critical Pile Length = 4.5

Design Soil Profile and Parameters:

Design Soil Parameters Co-efficients
Reduced Level, m Layer th.
Sl.No. Soil type SPT N c f g g' a K
m
2 3 3
From To kN/m deg. kN/m kN/m
1 Silty clay OR Sandy clay 0.0 4.0 4.0 8 15.0 26 18.0 8.0 1.00 1.00

2 Clayey silt 4.0 15.0 11.0 20 35.0 26 20.0 10.0 1.00 1.00

Calculation of Vertical Capacity:

Ultimate Capacity of Pile , Qult = Qb + Qs - W p
Where, Qb = Ultimate End Bearing
Qs = Ultimate Skin Resistance
Wp = Self weight of Pile Qsafe = Qult / FoS
Skin friction resistance, Qf = KPtanδ As + αCAs
K = Coefficient of earth pressure
P = Effective overburden pressure
δ = Angle of wall friction between pile and soil
As = Surface area of pile shaft
α = Adhesion factor
C = Average cohesion throughout the length of the pile

End bearing resistance in granular soils, Qe = Ap x PdxNq

Ap = Cross sectional area of the pile toe
D = Pile Diameter
ϒ = Effective unit weight of soil at pile toe
Pd = Effective overburden pressue at pile toe
Nϒ and Nq are the bearing capacity factors depending upon the angle of internal friction φ at toe.

End bearing resistance in Cohesive soil, Qe = Ap x CPxNC

Ap = Cross sectional area of the pile toe
CP = Avg. Cohesion at the pile tip
NC = Bearing capacity factor usually taken as 9
Calculation of Skin Resistances:
Layer-1: Layer thickness, L1 = 4.0 m
Pile embedment in the layer,h1 = 3.0 m
Ultimate Skin Resistance, Qs1 = (K1*P1*tanδ1+a1*c1 ) x As1
Earth pressure co-efficient K1 = 1.0
Overburden pressure P1 = 12 kN/m2
Reduction factor, a = 1.00
Cohesion, c1 = 15 kN/m2
Friction Angle, δ1 = 26 Deg
Surface area of Pile in layer 1, As1 = π * D * h1 = 2.83 m2
Ultimate Skin Resistance, Qs1 = = 59 kN

Layer-2: Layer thickness, L2 = 11.0 m

Pile embedment in the layer,h2 = 11.0 m
Ultimate Skin Resistance, Qs2 = (K2*P2*tanδ2+a2*c2 ) x As2
Earth pressure co-efficient K2 = 1.0
Overburden pressure P2 = 39.0 kN/m2
Reduction factor, a = 1.0
Cohesion, c2 = 35 kN/m2
Friction Angle, δ2 = 26 Deg
Surface area of Pile in layer 2, As2 = π * D * h2 = 10.4 m2
Ultimate Skin Resistance, Qs2 = = 560 kN

Layer-3: Layer thickness, L3 = 0.0 m

Pile embedment in the layer,h3 = 0.0 m
Ultimate Skin Resistance, Qs3 = (K3*P3*tanδ3+a*c3 ) x As3
Earth pressure co-efficient K3 = 0.0
Overburden pressure P3 = 39.0 kN/m2
Reduction factor, a = 0.00
Cohesion, c3 = 0 kN/m2
Friction Angle, δ1 = 0 Deg
Surface area of Pile in layer 3, As3 = π * D * h3 = 0.0 m2
Ultimate Skin Resistance, Qs3 = = 0 kN

Layer-4: Layer thickness, L4 = 0.0 m

Pile embedment in the layer,h4 = 0.0 m
Ultimate Skin Resistance, Qs4 = (K4*P4*tanδ4+a*c4 ) x As4
Earth pressure co-efficient K4 = 0.0
Overbuden pressure P4 = 39.0 kN/m2
Reduction factor, a = 0.00
Cohesion, c4 = 0 kN/m2
Friction Angle, δ4 = 0 Deg
Surface area of Pile in layer 4, As4 = π * D * h4 = 0.0 m2
Ultimate Skin Resistance, Qs4 = = 0 kN
Layer-5: Layer thickness, L5 = 0.0 m
Pile embedment in the layer,h5 = 0.0 m
Ultimate Skin Resistance, Qs5 = (K5*P5*tanδ5+a*c5 ) x As5
Earth pressure co-efficient K5 = 0.0
Overbuden pressure P5 = 39.0
Reduction factor, a = 0.00
Cohesion, c5 = 0 kN/m2
Friction Angle, δ5 = 0 Deg
Surface area of Pile in layer 5, As5 = π * D * h5 = 0.0 m2
Ultimate Skin Resistance, Qs5 = = 0 kN

Layer-6: Layer thickness, L6 = 0.0 m

Pile embedment in the layer,h6 = 0.0 m
Ultimate Skin Resistance, Qs6 = (K6*P6*tanδ6+a6*c6 ) x As6
Earth pressure co-efficient K6 = 0.0
Overbuden pressure P6 = 39.0
Reduction factor, a6 = 0.00
Cohesion, c6 = 0 kN/m2
Friction Angle, δ6 = 0 Deg
Surface area of Pile in layer 6, As6 = π * D * h6 = 0.0 m2
Ultimate Skin Resistance, Qs6 = = 0 kN

Layer-7: Layer thickness, L7 = 0.0 m

Pile embedment in the layer,h7 = 0.0 m
Ultimate Skin Resistance, Qs7 = (K7*P7*tanδ7+a7*c7 ) x As7
Earth pressure co-efficient K7 = 0.0
Overbuden pressure P7 = 39.0
Reduction factor, a7 = 0.00
Cohesion, c7 = 0 kN/m2
Friction Angle, δ7 = 0 Deg
Surface area of Pile in layer 7, As7 = π * D * h7 = 0.0 m2
Ultimate Skin Resistance, Qs7 = = 0 kN

Layer-8: Layer thickness, L8 = 0.0 m

Pile embedment in the layer,h8 = 1.0 m
Ultimate Skin Resistance, Qs8 = (K8*P8*tanδ8+a8*c8 ) x As8
Earth pressure co-efficient K8 = 0.0
Overbuden pressure P8 = 39.0
Reduction factor, a8 = 0.00
Cohesion, c8 = 0 kN/m2
Friction Angle, δ8 = 0 Deg
Surface area of Pile in layer 8, As8 = π * D * h8 = 0.9 m2
Ultimate Skin Resistance, Qs8 = = 0 kN
Total Ultimate Skin resistance, Qs = Qs1+Qs2+Qs3+Qs4+Qs5+Qs6+Qs7+Qs8 = 619 kN
Calculation of Ultimate End Bearing Resistance:
Ultimate End bearing Resistance, Qb = ((CP*NC)+(Pd*Nq)) * Ap
Where, Cohesion at Pile Toe, c = 0 kN/m2
Bearing Capacity Factor, Nc = 9
Eff. Overburden pressure at pile toe, Pd = 39.0 kN/m2
Eff. Overburden pressure at pile toe, Pd = 0.00
Eff. Overburden pressure at pile toe, Pd = 0.07 m2
Ultimate End bearing Resistance, Qb = ((CP*NC)+(Pd*Nq)) * Ap = 0 kN

Self Weight of the Pile, Wp

Self weight of the Pile , W p = Ap * ( Lbw * g'p )
Where, Area of pile, Ap = 0.07 m2
Total Length of Pile , L = 15 m
Unit Weight of Pile material below water, g'p = 15 kN/m3
Self weight of the Pile , W p = 16 kN

Ultimate Capacity of the Pile , Qult = Qb + Qs - Wp

Ultimate End Bearing, Qb = 0 kN
Ultimate Skin Resistance, Qs = 619 kN
Self weight of the Pile, W p = 16 kN
Ultimate Capacity of the Pile , Qult = Qb + Qs = 619 kN

Safe Capacity of Pile, Qsafe = ((ΣQsf/FOSsf)+(Qb / FoSb)-Wp

Factor of Safety against skin friction = 3.0
Factor of Safety against end bearing = 3.0
Safe Capacity of Pile, Qsafe = Qult / FoS (without -ve skin friction) = 190 kN
Uplift Capacity of the Pile
The uplift capacity contributed by top clay layer of 4m thickness is neglected in the analysis.
Ultimate Uplift Capacity of Pile , Qu = Qs + W p
Safe uplift capacity of the pile, Qusafe = Qu / FOS
Ultimate skin resistance for layer 1, Qs1 = 59 kN
Ultimate skin resistance for layer 2, Qs2 = 560 kN
Ultimate skin resistance for layer 3, Qs3 = 0 kN
Ultimate skin resistance for layer 4, Qs4 = 0 kN
Ultimate skin resistance for layer 5, Qs5 = 0 kN
Ultimate skin resistance for layer 6, Qs6 = 0 kN
Ultimate skin resistance for layer 7, Qs7 = 0 kN
Ultimate skin resistance for layer 8, Qs8 = 0 kN
Total ultimate skin resistance, Qs = 619 kN
Self weight of pile, W p = 16 kN
Ultimate uplift capacity of the pile, Qu = 2/3 * Qs + W p
= 429 kN
FOS = 3.0
Safe uplift capacity of the pile = 143 kN