1.
0 GENERAL
1.1 General
This calculation is prepared to check the Bored Pile Capacity for Cinyemeh River, Cilacap
1.2 Design Code and references
- ACI-318 2014: Building Code Requirement for Reinforec Concrete
- Principles of Foundation Engineering, 6th Edition, Braja M. Das, Thomson Learning, 2007
- FHWA-IF-99-025: Drilled Shafts: Construction Procedures and Design Methods
1.3 Design Data
1) Pile
- Type = Bored Pile
- Dimension, D = 600 mm
- Modulus of Elasticity, Ec = 25000 Mpa
2
- Pile Section, Ap = 0.28 m
2) Concrete
- Compressive strength of concrete, fc' = 35 Mpa
3
- Specific gravity of RC concrete, γc = 25 kN/m
- Modulus of Elasticity, Ec = 25000 Mpa
3) Reinforcing Steel Bar
- Use deformed rebar conform to SNI 07-2052-2002 BJTD 40
- Yield strength, fy = 460 Mpa
- Modulus of Elasticity, Es = 2.E+05 Mpa
- Cover for concrete protection, C = 60 mm
1.4 Design Criteria
- Factor of Safety for End Bearing, Fsbearing = 3.0
- Factor of Safety for Skin Friction, Fsfriction = 3.0
- Factor of Safety for Lateral Load, Fslateral = 3.0
2.0 GEOTECHNICAL PILE CAPACITY
2.1 BH-08A (Refer to Soilens' Report)
2.1.1 Subsoil Condition
BH-8A Pile Length = 30 m G.W.T (m) = -3.3
Depth of Layer (m) γ2) N3) N604) Su5)
from to center Soil Type1) (kN/m3) (blow) (blow) (kPa)
0.00 -4.15 -2.08 Cohesionless 16.70 11 11 48.40
-4.15 -8.15 -6.15 Cohesionless 19.20 14 14 61.60
-8.15 -18.15 -13.15 Cohesive 15.80 5 5 22.00
-18.15 -22.15 -20.15 Cohesive 16.20 20 20 88.00
-22.15 -28.15 -25.15 Cohesive 15.80 34 34 149.60
-28.15 -32.15 -30.15 Cohesive 15.20 52 52 228.80
-32.15 -36.15 -34.15 Cohesive 16.20 43 43 189.20
-36.15 -46.15 -41.15 Cohesive 16.20 44 44 193.60
-46.15 -50.15 -48.15 Cohesive 16.20 62 62 272.80
-50.15 0.00
Cohesive 16.20 1254.00
Note:
1) "Cohesive" = clay or plastic sily, "Cohesionless" = sand, gravel or non-plastic silt
2) SPT N-value obtained from the field test
3) Corrected for hammer energy without overburden pressure correction
N60 = (ER/60) x N where, ER = SPT energy ratio = 60%
4) Cohesion of sc(take minimum value from following two equations)
K x N, where K = 4.4 kPa (Stroud, 1974)
29 x N0.7 (Hara et al, 1971)
2.1.2 Allowable Compression Capacity (Reese and O'Neill, 1999)
1) Base Resistance for Compression Loading
a) Cohesive soil
qmax = Nc* x su = 1722.6 kpa
where, Nc* = bearing capacity factor = 9
6.50 at su = 24 kPa
8.00 at su = 48 kPa
9.00 at su > 25 kPa
su = average undrained shear strength between the base of the pile and
an elevation 2B below the base
= 191.40 kPa
b) Cohesionless soil
qmax = 57.5 N60 = 0 kPa
where, N60 = average SPT blow count between the base of the pile and
an elevation 2B below the base for condition which approximately
60 percent of the potential energy of hammer is transferred
2) Side Resistance for Compression Loading
a) Cohesive soil
fmax = α x su
where, α = a dimensionless correction coefficient defined as follows:
α= 0 between the ground surface and a depth of 1.5 m or to the
depth of seasonal moisture change, whichever is deeper
α= 0 for a distance of B (the diameter of the base) above the base
α = 0.55 for su / pa < 1.5 (Mpa)
α = 0.55 - 0.1 (su/ Pa - 1.5) for 1.5 < su / pa < 2.5 (Mpa)
Pa =the atmospheric pressure in the units being used
(e.g., 101 kPa in the SI system).
b) Cohesionless soil
fmax = ϐ x σ'v
where, σ'v = vertical effective stress at the middle of layer
ϐ = dimensionless correction factor defined as follows:
in sands
ϐ = 1.5 - 0.245 z0.5 for N60 > 15B / 0.3 m
0.5
ϐ = (N60/15) x (1.5 - 0.245 z ) for N60 < 15B / 0.3 m
in gravelly sands or gravels
ϐ = 2.0 - 0.15 z0.75 for N60 > 15B / 0.3 m
0.5
ϐ = (N60/15) x (1.5 - 0.245 z ) for N60 < 15B / 0.3 m
where, z = vertical distance from the ground surface to the middle
Layer N60 Su σ'v fmax Thick 1) As Qs
No. (blow) (kPa) ϐ (kPa) α (kPa) (m) (m2) (kN)
1 11 48.40 0.84 34.7 0.55 29.1 3.00 5.7 164.8
2 14 61.60 0.83 90.1 0.55 75.1 4.00 7.5 566.0
3 5 22.00 0.20 111.1 0.55 12.1 10.00 18.8 228.1
4 20 88.00 0.53 161.1 0.55 48.4 4.00 7.5 364.9
5 34 149.60 0.27 183.0 0.55 82.3 6.00 11.3 930.6
6 52 228.80 0.15 194.9 0.47 108.3 4.00 7.5 816.8
7 43 189.20 0.07 250.6 0.51 97.0 3.00 5.7 548.5
8 44 193.60 -0.07 295.3 0.51 98.4
9 62 272.80 -0.20 340.1 0.43 117.3
SUM 3619.7
1)
Note: Thickness of layer
3) Allowable compression capacity
Qall = (qmax x Ap)/ Fsbearing + Qs/ Fsfriction = 1368.9 kN
2.1.3 Allowable Tension Capacity (Reese and O'Neill, 1999)
1) Base Resistance for Uplift Loading
a) Cohesive soil
qmax uplift 1) = 0 kpa
Note: 1) qmax should be taken as zero for uplift loading unless experience or load testing at
the construction site can show that suction between the bottom of the drilled shaft
and the soil can be predicted reliably or the drilled shaft has a bell.
2) Side Resistance for Uplift Loading
fmax uplift 1) = ψ x fmax compression
where, ψ = 1.00 for Cohesive soil
ψ = 0.75 for Cohesionless soil
Soil Type Qs ψ Ts
(kN) (kN)
Cohesionless 164.8 0.75 123.6
Cohesionless 566.0 0.75 424.5
Cohesive 228.1 1.00 228.1
Cohesive 364.9 1.00 364.9
Cohesive 930.6 1.00 930.6
Cohesive 816.8 1.00 816.8
Cohesive 548.5 1.00 548.5
sum = 3437.0
3) Allowable Tension Capacity
Tall = (Tp + Ts)/ Fsfriction = 1145.7 kN
2.1.4 Allowable Lateral Load Capacity (Broms' Method)
1) Coefficient of horizontal subgrade reaction
1)
a) General soil type : Cohesionless
Note: 1) Determine the general soil type within the critical depth below the ground
surface (about 4 or 5 pile diameters).
b) Average soil parameter with the critical depth
su = 48.40 kPa for Cohesive soil
φ = 29.8 deg for Cohesionless soil
1)
where, φ = Internal friction angle correleted by Ozaki's equation
Note: 1) φ = (20 N)0.5 + 15
c) Coefficient of horizontal subgrade reaction, Kh
Kh = n1 x n2 x 80 x qu / b = 5343.4 kN/m3 for Cohesive oil
where, qu = Unconfined compressive strength = 2 su = 96.8 kPa
b = Width or diameter of pile = 0.6 m
n1 = Empirical coefficients dependent on qu = 0.36
= 0.32 for less than 48 kPa
= 0.36 for 48 to 191 kPa
= 0.40 for more than 191 kPa
n2 = Empirical coefficient dependent on pile material = 1.15
= 1.00 for steel
= 1.15 for concrete
= 1.30 for wood
Kh = 1900 kN/m3 for Cohesionless oil
where, above ground water
Kh = 1900 kN/m3 for loose density
= 8143 kN/m3 for medium density
= 17644 kN/m3 for dense density
below ground water
Kh = 1086 kN/m3 for loose density
= 5429 kN/m3 for medium density
= 10857 kN/m3 for dense density
2) Pile Parameters
a) Modulus of elasticity, E = 25000 Mpa
b) Moment of inertia, I = 0.0064 m4
c) Section modulus, S = 0.0212 m3
d) Embedded pile length, D = 30 m
e) Diameter or width, b = 0.6 m
f) Ultimate compression strength for concrete, f'c = 35 Mpa
g) Eccentricity of applied load for free-headed piles, ec = 0
h) Resisting moment of pile for concrete piles, My = f'c S = 742.2 kN-m
3) Dimensionless length factor
a) Stiffness factor
βh = ( Kh b / 4EI )0.25 = 0.27 m-1 for Cohesive oil
-1
η = (Kh / EI)0.20 = 0.4125 m for Cohesionless oil
b) Length factor
βh D = 7.99 for Cohesive oil
ηD = 12.38 for Cohesionless oil
4) Determine if the pile is long or short
a) Cohesive soil: long pile
where, βh D > 2.25 (long pile)
βh D < 2.25 (short pile)
b) Cohesionless soil: long pile
where, η D > 4.0 (long pile)
η D < 2.0 (short pile)
2.0 < η D < 4.0 (intermediate pile)
→ Soil type: Cohesionless
→ Pile type: long pile
5) Soil parameters
cu = 48.40 kPa for cohesive soil
where, cu = cohesion for cohesive soil
Kp = 2.9798 for cohesionless soil
where, Kp = Rankine passive earth pressure coefficient = tan2(45+φ/2)
6) Ultimate lateral load (Cohesionless, long pile)
a) For Cohesive soil
My/cub3 = 70.994
ec/b = 0
Qu/cub2 = from the chart
Qu = 0 kN
b) For Cohesionless soil
My/Kpγb4 = 100.1
3
where, γ = 19.20 kN/m
=
ec/b 0
4 = 76.2 from the chart
Qu/Kpγb
Qu = 565 kN
Broms's solution for ultimate lateral resistance of long piles
(a) in sand (b) in clay
Reference: Braja M. Das (page 465)
7) Allowable lateral load capacity
Hu = 565.0 kN
Hall = Hu / FSlateral = 188.3 kN
2.1.5 Result for pile capacity
1) Pile Capacity for Axial Compression, Pall = 1300 kN
2) Pile Capacity for Axial Tension, Tall = 1100 kN
3) Pile Capacity for Lateral Force, Hall = 180 kN
