the use of pile in deep foundation_3

7/30/2019 The Use of Pile in Deep Foundation_3

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3.3.2 Pile alternative design 2 - Precast concrete pile

Table 3.6 Soil Design Parameters

Soil Layer SPT Friction Data of Soil Design

Layer From To Depth N Angle Parameters were

(m) (m) (m) taken from Tables2-7, 3-4, Foundation

Analysis & Design,

(Bowles, J.E., (1989))

Design Considerations:

1. The pile foundation that will be designed is for an assumed bridge structure.

3. Water level is being assumed to be at or just below ground surface.

4. Initial and draft calculations were performed and a preliminary number of piles and

pile section was selected and the final design calculations will be presented here.

Table 3.7 Summary of LoadsLoad Axial

Case Load

# (Kn)

1

Max.

Axial

Load

2

Max.

Over

turning

3

Max.

Horiz.

Load

Medium

Dense Sand

150

SLS 6300 5180 200 1900 40

ULS 6480 6900 600 2800

ULS 0 3000

SLS 6400 5120 200 1900

79206640

ULS

SLS

8350 0 3000

2006400

(Kn)

1900

Mx My Py

Lateral Load

5182

40

SLS

(Kn-m)

Moment

about Y - Dir.

(Kn-m)

Px

0

40

along Y - Dir.

3.3.2.2 Foundation loads and load combinations

ULS Moment Lateral Load

150000-29.5 -40.5

Very

50 47

2

3

4 22

about X - Dir.

Dense Sand

13

10

11

Dense Sand

long X - Dir

(Kn)

8010

0 -6.5

-19.5 -29.5 39

-6.5

0

Loose Sand

Code/ReferenceCalculation/Discussion

3.3.2.1 Subsurface conditions and geotechnical descriptions

Soil

6.5

Bulk

1

Soil Elev. Modulus

Density of Elasticity

sat, (Kn/m3)

4

18 35 6250-19.5

E, (Kn/m2)

80000

12

20

Description

40

25 4750

10

62


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Y-Axis Ps PsyMsy

Psx

Msx

L B

Note: Direction of Traffic is along Y-axis.

Figure 3.5 Schematic Diagram of Foundation Loads

Presumed bearing value of loose sand = 30 KPa (1995))

Maximum Axial Service Load, Ps => = 6400 KN B= 4.75 m

Length of Foundation, L => L= 15.3 m

Afd= BxL => Afd= 72.7 m2

Depth of Underside of footing, Df= 2.5 m

3.3.2.3 Verify the requirement of a pile foundation

X-Axis

Afd =

63


3/23


Maximum Allowable Eccentricity of Loads

eallow = 0.3B => = 1.425 m Supplement to CHBDC S6-00

Section 6.7.3.4

Actual Load Eccentricity (Factored Loading from Load Case 2)

Mux The actual eccentricity is less than

Pu the allowable, eccentricity

requirement is complied.

Check for the Footing Settlement

qo(')(1-2)IsIf


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Calculate for shape Factor, Is, => (2-)F2(1-)

For: = 0.7976

m'= 3.221 F1

= 0.66


5/23


Design Consideration:

1. Preliminary Pile Size 450 450 Grade 50

b= 450 mm Ag= 2.E+05 mm2

d= 450 mm Sx= 2E+07 mm3

2. Initial No. of H-Piles => 22 Piles

2. Pile Cap Dimension 4.75 15.3 1.5 m

3. Minimum pile spacing 3xPile Dia. = 1.35 m


6/23


Maximum Design Load For a Single Pile

b Pu

Mux

o

a

R1 R2

Figure 3.7 Sectional View of Footing

From Summary of Loads; From preliminary footing dimensions,

Pu= 8010 KN a= 2.95 m

Mux= 8350 KN-m b= 1.475 m

@ Point "o" =0 Calculate for R2

(R2 x a) - Mx - Pu x b = 0 Mux + Pu x b

a

= 6836 KN

F =0 Calculate for R1

R2 + R1 - Pu = 0 R1= 1174 KN

Axial Load per single pile,

R2

No of Piles

= 621.4 KN

R2=

Ru=

67


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Check the Adequacy of Preliminary RC Pile Size

Capacity of Pile;

For a 450 450 Grade 50 concrete section with, = 1.50%

Pr,max= 4.5 MN 621.4 KN OK Concrete Design

Handbook - Part 2

(MacGregor, J.G.,

Longitudinal steel reinforcement requirement; et al, (2006))

1% t 4% 13.00 z= Segments of Pile embedment Length, L

2= 18 At= Pile toe cross sectional area

qt= Soil bearing stress at pile toe.

L= 27.03 m Wp = Weight of pile

w= Unit weight of water (9.81 kN/m3)

Dense

Sand

L3=> 10 For shaft resistance of pile

3= 20

@ Loose sand layer

Very L4=> 11 qs= v'


8/23


Thus, at Loose sand layer; = 0.3


9/23


So, pile point bearing resistance, Rt

Rt= At qt

= 8647 KN

Therefore:

R= Rt Rs Wp = 11340 KN

4536 KN where; The value of R > 621.4 KN OK!

= 0.4


10/23


Discussion:

1. The Canadian Foundation Engineering Manual recommends the use of wave

equation analysis for all calculation of pile driving capacity. This analysis gives

a more reliable results than the conventional dynamic equations. However, the

use of wave equation analysis involves the use of commercially available

computer software. In the absence of the wave equation software, a modified

Gates dynamic formula will be used to estimate the pile driving capacity.

2. The research paper, Recent advances in the design of piles for axial loads,

dragloads, downdrag, and settlement, B.H. Fellenius, 1998, it stated that

" regardless of whether of not the settlement of the ground surface is of

noticeable magnitude all piles will develop skin friction and dragloads"

3. A downdrag force will be included in the calculation. In the absence of


11/23


Using Delmag D55 Hammer

W= 11900 Lbs.

= 5.95 Ton

H= 9 Ft

= 108 inches

For a pile driving resistance, R= 421.7 Ton and calculating the value of S;

S= 0.073 inch/Blow

From the modified Gates dynamic formula, it can be shown that;

Let : 1

9 efWH N

where, N= Number of Hammer blows per inch of penetration

Further simplifying the above equation, gives;

Table 3.8: 1/set and Pile driving capacity

N

10N= 10 Ton KN

1 198 1761

Note: Values tabulated in Table 3.8 for Pile 3 292 2598

driving resistance is obtained using the 5 336 2989

above equation. 7 364 3238

9 386 343411 403 3585

13 418 3719

15 430 3825

Maximum permissible stress during pile driving

max= 0.85f'c = 1.00


12/23


Calculate for factored axial resistance during pile driving,

R= ( R - 75 % of Rs ) From Table 3.8, R= 3825.3 KN

= 0.4 621 KN Canadian Foundation

Engineering Manual

2006

Pu Muxeb MuyeL


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Table 3.9 Load per pile @ Load Case 1 in ULS loading

Pile Pu

No. n

(m.) (m.) (KN)1 1.475 2.1756 6.75 45.6 364.1

2 1.475 2.1756 5.4 29.2 364.1

3 1.475 2.1756 4.05 16.4 364.1

4 1.475 2.1756 2.7 7.29 364.1

5 1.475 2.1756 1.35 1.82 364.1

6 1.475 2.1756 0 0 364.1

7 1.475 2.1756 1.35 1.82 364.1

8 1.475 2.1756 2.7 7.29 364.1

9 1.475 2.1756 4.05 16.4 364.1

10 1.475 2.1756 5.4 29.2 364.1

11 1.475 2.1756 6.75 45.6 364.1

12 -1.48 2.1756 -6.8 45.6 364.1

13 -1.48 2.1756 -5.4 29.2 364.1

14 -1.48 2.1756 -4.1 16.4 364.1

15 -1.48 2.1756 -2.7 7.29 364.1

16 -1.48 2.1756 -1.4 1.82 364.1

17 -1.48 2.1756 0 0 364.1

18 -1.48 2.1756 -1.4 1.82 364.1

19 -1.48 2.1756 -2.7 7.29 364.1

20 -1.48 2.1756 -4.1 16.4 364.1

21 -1.48 2.1756 -5.4 29.2 364.1

22 -1.48 2.1756 -6.8 45.6 364.1

e2 => 47.864 401

eb2

() ()

eL2eL

eL2

257.3

Muxeb MuyeL Load/pile

KNeb2

eb

257.3

257.3

257.3

257.3

()

257.3

257.3

257.3

257.3

257.3

257.3

-257.3

-257.3

-257.3

-257.3

-257.3

-257.3

-257.3

-257.3

-257.3

-257.3

-257.3

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

621.4

621.4

621.4

621.4

621.4

106.8

106.8

621.4

621.4

621.4

621.4

621.4

621.4

106.8

106.8

106.8

106.8

106.8

106.8

106.8

106.8

106.8

+

74


14/23


Calculate the axial load for each pile at various load cases, and tabulating the summary;

Table 3.10 Summary of pile axial load for load cases 1, 2, & 3 in ULS and SLS loadings

Load

Case

P=

Mx=

My=

Pile

No.

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

1718

19

20

21

22

1

ULS SLS

2

ULS SLS

3

ULS SLS

8010

8350

0

6400

5182

200

6640

0

6400

5120

200

6480

6900

600

6300

5180

200

621.4 454.0 545.9 452.1 517.3 449.4

7920

621.4 453.3 545.9 451.4 515.3 448.7

621.4 452.6 545.9 450.7 513.2 448.0

621.4 451.9 545.9 450.0 511.2 447.3

621.4 451.3 545.9 449.4 509.2 446.7

621.4 450.6 545.9 448.7 507.2 446.0

621.4 451.3 545.9 449.4 509.2 446.7

621.4 451.9 545.9 450.0 511.2 447.3

621.4 452.6 545.9 450.7 513.2 448.0

621.4 453.3 545.9 451.4 515.3 448.7

621.4 454.0 545.9 452.1 517.3 449.4

106.8 127.9 57.8 129.8 71.8 123.4

106.8 128.5 57.8 130.4 73.8 124.0

106.8 129.2 57.8 131.1 75.9 124.7

106.8 129.9 57.8 131.8 77.9 125.4

106.8 130.5 57.8 132.5 79.9 126.1

106.8 131.2 57.8 133.1 81.9 126.7106.8 130.5 57.8 132.5 79.9 126.1

106.8 129.9 57.8 131.8 77.9 125.4

106.8 129.2 57.8 131.1 75.9 124.7

57.8 129.8 71.8 123.4

106.8 128.5 57.8 130.4 73.8 124.0

106.8 127.9

75


15/23


Lateral capacity of piles in soils by Brom's Method


16/23


Calculate for Qu at xo= 10 mm

0.93Qu


17/23


Calculate for elastic deformation of pile shaft, Sp ;

QL 454.0 KN

L= Total embedment length of pile => 27.03 m

Ag= Cross section of pile => 0.203 m2

E= Modulus of elasticity of material => 3E+07

Calculate,

Sp= 1.43 mm

Calculate settlement due to load at pile shaft,

Qsa where


18/23


Calculate ultimate lateral passive resistance of a pile group;

Qu= 0.5BL2Kp 2.95 m (Tomlinson, M.J.,

= Submerged density of soil => 1.10 (1977))

Kp= Coeff of passive pressure => 3.6902

L= Pile embedment => 27.03 m

Calculate ultimate lateral passive resistance, Qug

Qu= 42898 KN So, Quallow = 17159 2.5

Quallow = 17159 KN > 1900 KN OK!

Calculate settlement of a pile group;

B 2.091 mm

B= width of pile group => 2.95 m

D= Diameter of single pile => 0.45 m

5.35 mm < 25 mm OK!

Allowable settlement for a pile group, Sgroup = 25.00 mm


19/23


where

n1= No. of columns in plan => 11

n2= No. of rows in plan => 2

d= Spacing of pile => 1.35 m

D= Pile Dia. => 0.45 m

p= section perimeter of pile => 1.8 m

calculate for the value of n,

n= 0.7955

Pu= n R

= 79379 KN > 8010 KN OK!

Calculate pile section bending moment capacity

Estimate the steel reinforcement requirement for axial and bending resistance;

Consider Load Case 1

Loads per single pile,

Mux= 379.55 KN-m => 0.38 MN-m

Muy= 0.00 KN-mRu= 621.4 KN => 0.621 MN

= 3.069 MPa

thus, = 0.032


20/23


Try actual = 0.037 , For a value of = 0.037 Kr= 9.50 5828 mm2

; Try 8 - 30mm rebars Handbook - Part 2

Actual, As= 5600 mm2

say OK! (MacGregor, J.G.,Actual = 0.036 < b OK et al, (2006))

Calculate bending moment capacity, Mrx

where, d= h - cover - ds - => 350.00 mm

b= 450 mm

cover= 75 mm

ds= 10 mm

db= 30 mm

Mrx= Krbd2 x 10-6 KN-m => 524 KN-m


21/23


Consider Load Case 3;

Mux= 313.64 KN-m Mrx= 523.7 KN-m

Muy

= 27.27 KN-m Mry

= 523.7 KN-m

Ru= 517.3 KN Pucap= 4231 KN

Ru Mux Muy

R Mrx Mry

517.3 314 27.27

4231 524 523.7

0.122 + 0.60 + 0.05 = 0.77 < 1 OK!

Single pile maximum factored shear force; Vf

Vf= 136.36 KN

Concrete section shear resistance;

Vc= c f'c bwdv


22/23


Section area provided by one stirrup, Av

Av= 200.0 mm2

Calculate the spacing of 10M stirrups, s;

sAvfydvcot


23/23


Minimum tie spacing requirement;

the use of pile in deep foundation_3

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