pile capacity

1.0 Input

1.1 Design Soil Parameters

c f gSub k d a

From To From To kN/m2

deg. kN/m3

deg.

1 Fill 0 -2 0.0 2.0 0 0 6 0

2 Silty Clay -2 -7 2.0 7.0 15 0 7 0 0 0.3

3 Silty Sand -7 -11 7.0 11.0 0 30 8 2 30 0

4 Silty Sand -11 -16 11.0 16.0 0 32 8 2 32 0

5 Sand -16 -20 16.0 20.0 0 30 9 2 30 0

6 Silty Sand -20 -25 20.0 25.0 10 28 9 1.5 28 0.3

1.2 Pile Details

Existing ground level = 0 m

Pile Diameter, D = 0.4 m

Pile Cut-off level = -1.4 m

Dredge level = -1.4 m

Scour level = -1.4 m

Pile Founding level = -13.4 m

Depth from G.L.corresponding to F.L. = 13.4 m

Pile Embedment length = 12.0 m

Total Pile Length, L = 12.0 m

Pile Density = 25.0 kN/m3

Factor of Safety = 2.5

Pile Fixity condition at top = fixed (Fixed or Free)

Grade of Concrete = 25 N/mm2

Modulus of subgrade reaction at fixity zone = 4000 kN/m3

Type of soil in fixity zone = Sand (Sand or Clay)

Unsupported Length of Pile, L1 = 0.0 m

Allowable displacement of pile at head = 7.0 mm

(For Horizontal capacity)

1.3 Sketch0 m, EBL

-1.4 m Cut-Off Level

-13.4 m, Found. Level

Reduced

Level

Depth of layer

from ground

Soil Parameters Interaction Parameters

Sl.No. Description

2.0 Calculation of Vertical Capacity

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

Whetre, Qb = Ultimate End Bearing

Qs = Ultimate Skin Resistance

Wp = Self weight of Pile

Qsafe = Qult / FOS

Where, FOS = Factor of Safety

2.1 Calculation of Skin Resistances

2.1.1 Layer-1:

Layer thickness, L1 = 2 m

Pile embedment in the layer, h1 = 0.6 m

Ultimate Skin Resistance, Qs1 = (a * c1 + K * Pd1 * tand ) x As1

Where, Reduction factor, a = 0

Cohesion, c1 = 0 kN/m2

Coefficient of Lateral earth pressure, K = 0

Unit weight of soil , g1 = 6 kN/m3

Effective Overburden Pressure at middle of layer, Pd1

Pd1 = h1/2 *g1 = 6 kN/m2

Angle of wall friction, d = 0 deg.

Surface area of Pile in layer 1, As1 = pi * D * h1 = 0.7536 m2

Ultimate Skin Resistance, Qs1 = (a*c1 + K*Pd1*tand ) x As1 = 0 kN

2.1.2 Layer-2:


Pile embedment in the layer, h1 = 5 m


Where, Reduction factor, a = 0.3



Unit weight of soil, g2 = 7 kN/m3


Pd2 = Pd1 + h1/2 *g1 + h2/2 *g2 = 29.5 kN/m2



Ultimate Skin Resistance, Qs2 = (a*c2 + K*Pd2*tand ) x As2 = 28.26 kN

2.1.3 Layer-3:


Pile embedment in the layer, h3 = 4 m







Pd3 = Pd2 + h2/2 *g2 + h3/2 *g3 = 63 kN/m2



Ultimate Skin Resistance, Qs3 = (a*c3 + K*Pd3*tand ) x As3 = 365.2526 kN

2.1.4 Layer-4:


Pile embedment in the layer, h4 = 2.4 m







Pd4 = Pd3 + h3/2 *g3 + h4/2 *g4 = 88.6 kN/m2



Ultimate Skin Resistance, Qs4 = (a*c4 + K*Pd4*tand ) x As4 = 334 kN

Total Ultimate Skin resistance, Qs = Qs1 +Qs2 +Qs3 +….. +Qsn = 727 kN

2.2 Ultimate End Bearing Resistance

Ultimate End bearing Resistance, Qb = (c* Nc + Pd * Nq ) * Ap

Where, Cohesion at Pile Toe, c = 0 kN/m2

Bearing Capacity Factor, Nc = 9

Effective overburden pressure at Pile tip, Pd

Pd = Pd6 + h6/2 *g6 = 98.2 kN/m2

Angle of internal friction at pile toe,f = 32

Bearing Capacity Factor, Nq = 30

Area of Pile at toe, Ap = 0.1256 m2

Ultimate End bearing Resistance, Qb = (c* Nc + Pd * Nq ) * Ap = 370 kN

2.3 Self Weight of the Pile, Wp

Self weight of the Pile , Wp = Ap * L * gp

Where, Area of pile, Ap = 0.1256 m2

Total Length of Pile , L = 12 m

Unit Weight of Pile material, gp = 15 kN/m3

Self weight of the Pile , Wp = Ap * L * gp = 23 kN

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

Where, Ultimate End Bearing, Qb = 370 kN

Ultimate Skin Resistance, Qs = 727 kN

Self weight of the Pile, Wp = 23 kN

Ultimate Capacity of the Pile , Qult = Qb + Qs - Wp = 1074 kN

2.5 Safe Capacity of Pile, Qsafe = Qult / FOS

Where, Ultimate Capacity of Pile, Qult = 1074 kN

Factor of Safety = 2.5

Safe Capacity of Pile, Qsafe = Qult / FOS = 430 kN

3.0 Tension Capacity of Pile

Ultimate Tension Capacity of the Pile , Qult(T) = 2/3 x Qs + Wp

Where, Ultimate Skin Resistance, Qs = 727 kN

Self weight of the Pile, Wp = 23 kN

Ultimate Tension Capacity of the Pile , Qult(T) = 2/3 x Qs + Wp = 507 kN

Safe Tension Capacity of the Pile , Qsafe(T) = Qult(T) / FoS

Where, FoS = Factor of Safety = 2.5

Safe Tension Capacity of the Pile , Qsafe(T) = Qult(T) / FoS = 203 kN

4.0 Fixity Depth Calculation

Pile fixity condition at top = fixed

Type of Soil in fixity zone = Sand

Modulus of subgrade reaction at fixity zone, K = 4000 kN/m3

Elastic modulus of concrete, Ec = 5000 * SQRT(fck)

Where, fck = Characteristic strength of concrete = 25 N/mm2

Elastic modulus of concrete, Ec = 5000 * SQRT(fck) = 25000 N/mm2

= 25000000 kN/m2

Moment of inertia of Pile, I = 3.14 /64 *D^4

where, D = Diameter of the pile = 0.4 m

Moment of inertia of Pile, I = 3.14 /64 *D^4 = 0.001 m4

Relative Stiffness factor, T = (EI/K)^(1/5) = 1.510 m

Unsupported length of pile, L1 = 0.0 m

Ratio of L1/T or L1/R = 0

Lf/T or Lf /R = = 2.18

Therefore, Fixity Depth , Lf = = 3.3 m

Fixity depth, in terms of diameter of pile = 8.23 times the dia

5.0 Minimum Pile Length for lateral Capacity

Minimum Pile Length for flexible pile, Lmin = > 4T

Where, T = Relative stiffness factor = 1.51 m

Let us consider a minimum length of pile , Lmin = 4.5 times T = 6.8 m

6.0 Horizontal Capacity of the Pile

Pile fixity condition at top = fixed

The horizontal capacity, H = 12*E*I*y / (L1+Lf)^3

Where, y = Diaplacement of pile at head = 0.007 m

E = Elastic modulus of pile material = 25000000 kN/m2

I = Moment of inertia = 0.001 m4

L1 = Unsupported length of pile = 0.00 m

Lf = Fixity length of pile = 3.29 m

The horizontal capacity, H = 12*E*I*y / (L1+Lf)^3 = 73.95 kN

7.0 Summary of Calculations

Pile Diameter = 0.40 m

Pile Cut-off level = -1.4 m

Pile Founding Level = -13.4 m

Safe Vertical Capacity = 430 kN

Safe Tension Capacity = 203 kN

Pile head Condition = fixed

Grade of Concrete = 25.00 N/mm2

Horizontal capacity for a Displacement of 7.0 mm = 74 kN

Minimum Pile length for Lateral Capacity = 6.8 m

Fixity Depth, Lf = 3.3 m

pile capacity

Documents