1. INTRODUCTION TO STATIC ANALYSIS
Reference Manual Chapter 9

2. Lesson 2 – Learning Outcomes
You will be able to:
List 3 reasons why a static analysis is performed.
Discuss what makes a “good” static analysis method.
Calculate effective overburden pressure versus depth.
Review that objective was achieved.

3. CHAPTER 9 - STATIC ANALYSIS
● Single pile design issues
● Group design issues
● Special design considerations
● Additional design and construction considerations

4. STATIC ANALYSIS METHODS
Static analysis methods and computer solutions are used to:
● Calculate pile length for loads
● Determine number of piles
● Determine most cost effective pile type
● Calculate foundation settlement
● Calculate performance under uplift and lateral loads

5. STATIC ANALYSIS METHODS
Static analysis methods and computer solutions are an integral part of the design process.
Static analysis methods are necessary to determine the most cost effective pile type.
For a given pile type:
- calculate capacity
- determine pile length
Bid Quantity
- determine number of piles

6. STATIC ANALYSIS METHODS
Foundation designer must know design loads and performance requirements.
Many static analysis methods are available.
- methods in manual are relatively simple
- methods provide reasonable agreement with full scale tests
- other more sophisticated methods could be used
Designer should fully know the basis for, limitations of, and applicability of a chosen method.

7. BASICS OF STATIC ANALYSIS
Static capacity is the sum of the soil/rock resistances along the pile shaft and at the pile toe.
Static analyses are performed to determine ultimate pile capacity and the pile group response to applied loads.
The ultimate capacity of a pile and pile group is the smaller of the soil rock medium to support the pile loads or the structural capacity of the piles.

8. BASICS OF STATIC ANALYSIS
Static analysis calculations of deformation response to lateral loads and pile group settlement are compared to the performance criteria established for the structure.
Static analyses are performed using geotechnical evaluation of soil properties from laboratory test, standard penetration test results, or in-situ test data.
On many projects, multiple static analyses are required.

9. Qu = (Design Load x FS) + “other”
ULTIMATE CAPACITY
Qu = (Design Load x FS) + “other”
“Other” could be the resistance provided by scourable soil
“Other” could be the resistance provided by Liquefiable soil
“Other” is soil resistance at the time of driving
not present later during the design life of the pile

10. TWO STATIC ANALYSIS ARE OFTEN REQUIRED
First analysis with scourable soil
removed, this will give us required
pile length for the given ultimate capacity.
Second analysis with scourable soil
in place and with pile length from first
analysis, this will give us our ultimate
static resistance at time of driving
Liquefaction ?

11. TWO STATIC ANALYSIS REQUIRED

12. COHESIONLESS SOILS s b 3 – 5.5b 3 – 5b b = pile diameter
s = settlement

13. COHESIVE SOILS H
H = heave
high pore water pressure zone b 3b

14. LOAD TRANSFER
The ultimate pile capacity is typically expressed as the sum of the shaft and toe resistances:
Qu = Rs + Rt
This may also be expressed in terms of unit resistances:
Qu = fs As + qt At
The above equations assume that the ultimate shaft and toe resistances are simultaneously developed.

15. Soil Resistance vs Depth
LOAD TRANSFER Qu
Axial Load vs Depth
Soil Resistance vs Depth
Rs = 0 Rs Rt Rt
Uniform Rt Rs
Triangular Rt Rs

16. EFFECTIVE OVERBURDEN PRESSURE
The effective overburden pressure at a given depth is the vertical stress at that depth due to the weight of the overlying soils.
A plot of the effective overburden pressure versus depth is called a po diagram and is used in many static analysis methods.

17. EFFECTIVE OVERBURDEN PRESSURE
The total overburden pressure at a given depth is obtained from summing the product of the total unit weight times the layer thickness versus depth.
pt =  (depth)
The pore water pressure is summed versus depth by multplying the unit weight of water times the water height
u = w (depth)

18. EFFECTIVE OVERBURDEN PRESSURE
The effective overburden pressure at a given depth is the total pressure minus the pore water pressure.
po = pt - u

19. EFFECTIVE OVERBURDEN PRESSURE
158.1
(614 lb/ft2)
(2683 lb/ft2)
275.7
187.5

20. EFFECTIVE OVERBURDEN PRESSURE
185.1
302.7
(2456 lb/ft2)
(1406 lb/ft2)
67.5
126.3
(2736 lb/ft2)
176.4

21. STUDENT EXERCISE #1
Figure 9.7 on page 12 shows the effect of water table location on effective stresses. Low water table results in higher effective stresses, higher shear strength, and therefore higher driving resistances

22. Soil Profile

23. Unit Weight of Soil Layer
STUDENT EXERCISE #1
Depth
(m)
Layer Thickness t
Unit Weight of Soil Layer 
(kN/m3)
Overburden
Pressure
from Layer,
t ()
(kPa)
Total
at Depth
pt=∑ t ()
Unit Weight
of Water w
Pore Water
from Layer
t w
Total Pore
Water
u=G t (w)
Effective
po=pt-u
15.0
- - - 5 75 10
150
9.8 49
101 20
17.5
175
325 98
147
178 35 15
20.0
300
625
294
331

27. DESIGN SOIL STRENGTH PARAMETERS
Most of the static analysis methods in cohesionless soils use the soil friction angle determined from laboratory tests or SPT N values.
In coarse granular deposits, the soil friction angle should be chosen conservatively.
What does this mean ??

28. DESIGN SOIL STRENGTH PARAMETERS
In soft, rounded gravel deposits, use a maximum soil friction angle, , of 32˚ for shaft resistance calculations.
In hard, angular gravel deposits, use a maximum friction angle of 36˚ for shaft resistance calculations.

29. DESIGN SOIL STRENGTH PARAMETERS
In cohesive soils, accurate assessments of the soil shear strength and consolidation properties are needed for static analysis.
The sensitivity of cohesive soils should be known during the design stage so that informed assessments of pile driveability and soil setup conservatively can be made.

30. DESIGN SOIL STRENGTH PARAMETERS
For a cost effective design with any static analysis method, the foundation designer must consider time dependent soil strength changes.

31. FACTOR OF SAFETY SELECTION
Historically, the range in factor of safety has depended upon the reliability of a particular static analysis method with consideration of :
● Level of confidence in the input parameters
● Variability of soil and rock
● Method of static analysis
● Effects of, and consistency of proposed pile installation method
● Level of construction monitoring

32. Construction Control Method
FACTORS OF SAFETY
The factor of safety used in a static analysis should be based on the construction control method specified.
Construction Control Method
Factor of Safety
Static load test with wave equation analysis
2.00
Dynamic testing with wave equation analysis
2.25
Indicator piles with wave equation analysis
2.50
Wave equation analysis
2.75
Gates dynamic formula
3.50
9-14

33. EXAMPLE SOIL PROFILE

34. EXAMPLE SOIL PROFILE Ultimate Capacity: Qu = Rs1 + Rs2 + Rs3 +Rt
Design Load: Qa = (Rs3 + Rt) / FS
Soil Resistance to Driving:
SRD = Rs1 + Rs2 + Rs3 +Rt
(with no soil strength changes)
SRD = Rs1 + Rs2 / 2 + Rs3 +Rt
(with clay soil strength change)

35. Lesson 2 – Learning Outcomes
You will be able to:
List 3 reasons why a static analysis is performed.
Discuss what makes a “good” static analysis method.
Calculate effective overburden pressure versus depth.
Review that objective was achieved.

36. Static Analysis - Single Piles
Methods for estimating static resistance of soils

37. Lesson 7 – Learning Outcomes
You will be able to:
Identify the FHWA recommended static analysis methods in cohesionless and cohesive soils.
Calculate, by hand, the axial compression capacity of a single pile in cohesionless, cohesive, and layered soils.
Review that objective was achieved.

38. Lesson 7 – Learning Outcomes
You will be able to:
Determine when the axial compression capacity is controlled by the structural pile capacity.
Discuss the DRIVEN software for axial compression capacity calculations.
Review that objective was achieved.

39. STATIC CAPACITY
OF PILES IN
COHESIONLESS SOILS

40. Pushing Force
Resistance

41. Cohesionless Soils, Drained Strength
Normal Force, N
Friction Force, F
F = N μ
μ = coefficient of friction between
material 1 and material 2 1 2 F N 
Tan () = F/N
F = N TAN ()
phi = angle such that TAN ()
is coefficient of friction between
material 1 and material 2
Soil on Soil, we use 
Soil on Pile, we use δ

42. METHODS OF STATIC ANALYSIS FOR PILES IN COHESIONLESS SOILS
Approach
Design
Parameters
Advantages
Disadvantages
Remarks
Meyerhof Method
Empirical
Results of SPT tests.
Widespread use of SPT test and input data availability. Simple method to use.
Non reproducibility of N values. Not as reliable as the other methods presented in this chapter.
Due to non reproducibility of N values and simplifying assumptions, use should be limited to preliminary estimating purposes.
Brown Method
Results of SPT tests based of N60 values.
N60 values not always available.
Simple method based on correlations with 71 static load test results. Details provided in Section b.
Nordlund Method.
Semi‑
empirical
Charts provided by Nordlund. Estimate of soil friction angle is needed.
Allows for
increased shaft resistance of tapered piles and includes effects of pile-soil friction coefficient for different pile materials.
No limiting value on unit shaft resistance is recommended by Nordlund. Soil friction angle often estimated from SPT data.
Good approach to design that is widely used. Method is based on field observations. Details provided in Section c.
Experience N
Part Theory Part Experience
FHWA
9-19

43. METHODS OF STATIC ANALYSIS FOR PILES IN COHESIONLESS SOILS
Approach
Design
Parameters
Advantages
Disadvantages
Remarks
Effective Stress Method.
Semi-empirical
Soil classification and estimated friction angle for β and Nt selection.
β value considers pile-soil friction coefficient for different pile materials. Soil resistance related to effective overburden pressure.
Results effected by range in β values and in particular by range in Nt chosen.
Good approach for design. Details provided in Section
Methods based on Cone Penetration Test (CPT) data.
Empirical
Results of CPT tests.
Testing analogy between CPT and pile. Reliable correlations and reproducible test data.
Limitations on pushing cone into dense strata.
Good approach for design. Details provided in Section
9-19

44. Nordlund Data Base Pile Types Pile Sizes Pile Loads
Timber, H-piles, Closed-end Pipe, Monotube, Raymond Step-Taper
Pile Types
Pile Sizes
Pile Loads
Pile widths of 250 – 500 mm ( in)
Ultimate pile capacities of kN ( tons)
Nordlund Method tends to overpredict capacity of piles greater than 600 mm (24 in)
9-25

45. Nordlund Method Considers: 1. The friction angle of the soil.
2. The friction angle of the sliding surface.
3. The taper of the pile.
4. The effective unit weight of the soil.
5. The pile length.
6. The minimum pile perimeter.
7. The volume of soil displaced.
9-25

46. 9-27

47. Nordlund Method Qu = (KδCFpd(sinδ)CdD) + (αtN’qAtpt) RS RT
For a pile of uniform cross section (=0) and embedded length D, driven in soil layers of the same effective unit weight and friction angle, the Nordlund equation becomes: RS RT
Qu = (KδCFpd(sinδ)CdD) + (αtN’qAtpt)

48. Nordlund Shaft Resistance
K = coefficient of lateral earth pressure
CF = correction factor for K when  ≠ 
pd = effective overburden pressure at center of layer
= friction angle between pile and soil
Cd = pile perimeter
D = embedded pile length
Figures
Figure 9.15
Figure 9.10

49. Nordlund Toe Resistance
RT = T N’q pT AT
Lesser of
RT = qL AT
T = dimensionless factor
N’q = bearing capacity factor
AT = pile toe area
pT = effective overburden pressure at pile toe ≤ 150 kPa
qL = limiting unit toe resistance
Figure 9.16a
Figure 9.16b
Figure 9.17

50. FS based on construction control method as in 9-14
Nordlund Method
Ru = RS + RT
and
Qa = RU / FS
FS based on construction control method as in 9-14

51. Nordlund Method Procedure
Steps 1 through 6 are for computing shaft resistance and steps 7 through 9 are for computing the pile toe resistance
STEP 1 Delineate the soil profile into layers and determine the  angle for each layer
Construct po diagram using procedure described in Section 9.4.
Correct SPT field N values for overburden pressure using Figure 4.4 from Chapter 4 and obtain corrected SPT N' values. Delineate soil profile into layers based on corrected SPT N' values.
Determine  angle for each layer from laboratory tests or in-situ data.
In the absence of laboratory or in-situ test data, determine the average corrected SPT N' value, N', for each soil layer and estimate  angle from Table 4-5 in Chapter 4.
9-28

52. Nordlund Method Procedure
STEP 2 Determine , the friction angle between the pile and soil based on the displaced soil volume, V, and the soil friction angle, .
Compute volume of soil displaced per unit length of pile, V.
Enter Figure 9.10 with V and determine / ratio for pile type.
Calculate  from / ratio.
9-28

53. Relationship Between Soil Displacement, V, and /
0.25
0.75
/ = 0.70
a – closed-end pipe and non-tapered Monotube piles
b – timber piles
c – pre-cast concrete piles
d – Raymond Step-Taper piles
e – Raymond uniform piles
f – H-piles
g – tapered portion of Monotube piles

54. Relationship Between Soil Displacement, V, and /
/ = 0.65
a – closed-end pipe and non-tapered Monotube piles
b – timber piles
c – pre-cast concrete piles
d – Raymond Step-Taper piles
e – Raymond uniform piles
f – H-piles
g – tapered portion of Monotube piles

55. Nordlund Method Procedure
STEP 3 Determine the coefficient of lateral earth pressure K for each soil friction angle, .
Determine K for each  angle based on displaced volume V, and pile taper angle, ω, using appropriate procedure in steps 3b, 3c, 3d, or 3e.
If displaced volume is , 0.093, or m3/m and the friction angle is 25, 30, 35, or 40, use Figures 9.11 to 9.14.
If displaced volume is given but  angle is not. Linear interpolation is required to determine K for  angle.
9-28

56. K versus ω
 = 25◦
Figure 9.11
9-33

57. K versus ω
 = 30◦
Figure 9.12
9-34

58. Nordlund Method Procedure
STEP 3 Determine the coefficient of lateral earth pressure K for each soil friction angle, .
If displaced volume is not given but  angle is given, log linear interpolation is required to determine K for displaced volume V.
If neither the displaced volume or  angle are given, first use linear interpolation to determine K for  angle and then use log linear interpolation to determine K for the displaced volume, V.
See Table 9-4 for K as function of  angle and displaced volume V
9-29

59. Table 9-4(a) Design Table for Evaluating K for Piles when ω = 0˚ and
V = to m3/m (0.10 to 1.00 ft3/ft) N
Displaced Volume -V, m3/m, (ft3/ft)
0.0093
(0.10)
0.0186
(0.20)
0.0279
(0.30)
0.0372
(0.40)
0.0465
(0.50)
0.0558
(0.60)
0.0651
(0.70)
0.0744
(0.80)
0.0837
(0.90)
0.0930
(1.00) 25
0.70
0.75
0.77
0.79
0.80
0.82
0.83
0.84
0.85 26
0.73
0.78
0.86
0.87
0.88
0.89
0.90
0.91 27
0.76
0.92
0.94
0.95
0.96
0.97 28
0.93
0.98
0.99
1.01
1.02
1.03 29
1.05
1.06
1.08
1.09 30
1.10
1.12
1.14
1.15 31
1.13
1.16
1.19
1.21
1.24
1.25
1.27 32
1.17
1.22
1.26
1.30
1.32
1.35
1.37
1.39 33
1.40
1.44
1.46
1.49
1.51 34
1.42
1.47
1.55
1.58
1.61
1.63 35
1.33
1.57
1.62
1.66
1.69
1.72
1.75 36
1.48
1.71
1.78
1.84
1.89
1.93
1.97
2.00 37
1.79
1.90
1.99
2.05
2.11
2.16
2.21
2.25 38
2.09
2.19
2.27
2.34
2.40
2.45
2.50 39
1.59
1.94
2.14
2.29
2.49
2.57
2.64
2.70
2.75 40
1.70
2.32
2.48
2.61
2.71
2.80
2.87
2.94
3.0

60. Nordlund Method Procedure
STEP 4 Determine the correction factor CF to be applied to K if  ≠ .
Use Figure 9.15 to determine the correction factor for each K. Enter figure with  angle and / ratio to determine CF.
9-29

61. Correction Factor for K when   
Figure 9.15

62. Nordlund Method Procedure
STEP 5 Compute the average effective overburden pressure at the midpoint of each soil layer.
STEP 6 Compute the shaft resistance in each soil layer. Sum the shaft from each layer to obtain the ultimate shaft resistance, RS.
9-30

63. Nordlund Method Procedure
STEP 7 Determine the αt coefficient and the bearing capacity factor, N'q, from the  angle near the pile toe.
a. Enter Figure 9.16(a) with  angle near pile toe to determine αt coefficient based on pile length to diameter ratio.
Enter Figure 9.16(b) with  angle near pile toe to determine, N'q.
c. If  angle is estimated from SPT data, compute the average corrected SPT N' value over the zone from the pile toe to 3 diameters below the pile toe. Use this average corrected SPT N' value to estimate  angle near pile toe from Table 4-5.
9-30

64. Nordlund Method Procedure
STEP 8 Compute the effective overburden pressure at the pile toe.
NOTE: The limiting value of pt is 150 kPa
STEP 9 Compute the ultimate toe resistance, Rt.
Use lesser of:
RT = T N’q pT AT
Figure 9-16a and 9-16b
RT = qL AT
Figure 9-17
9-30

65. αt Coefficient versus 
 (degrees)
Figure 9.16a

66. Figure 9.16 Chart for Estimating αt Coefficient and Bearing Capacity Factor N'q (Chart modified from Bowles, 1977)
Figure 9.16b

67. Limiting Unit Toe Resistance – (SI)
Figure 9.17

68. Limiting Unit Toe Resistance – (US)
Figure 9.17

69. Nordlund Method Procedure
STEP 10 Compute the ultimate capacity, Qu.
Qu = Rs + Rt
STEP 11 Compute the allowable design load, Qa.
Qa = Qu / Factor of Safety
9-31

70. STATIC CAPACITY OF PILES IN COHESIVE SOILS
9-42

71. Cohesive Soils, Undrained StrengthF N c
 = zero
F = Friction resistance ; N = Normal force (stress)
C is independent of overburden pressures
c = cohesion, stickiness, soil / soil
a = adhesion, stickiness, soil / pile

72. METHODS OF STATIC ANALYSIS FOR PILES IN COHESIVE SOILS
Approach
Method of Obtaining
Design Parameters
Advantages
Disadvantages
Remarks
α-Method
(Tomlinson Method).
Empirical, total stress analysis.
Undrained shear strength estimate of soil is needed. Adhesion calculated from Figures 9.18 and 9.19.
Simple calculation from laboratory undrained shear strength values to adhesion.
Wide scatter in adhesion versus undrained shear strengths in literature.
Widely used method described in Section a.
Effective Stress Method.
Semi-Empirical, based on effective stress at failure.
β and Nt values are selected from Table 9-6 based on drained soil strength estimates.
Ranges in β and Nt values for most cohesive soils are relatively small.
Range in Nt values for hard cohesive soils such as glacial tills can be large.
Good design approach theoretically better than undrained analysis. Details in Section
Methods based on Cone Penetration Test data.
Empirical.
Results of CPT tests.
Testing analogy between CPT and pile. Reproducible test data.
Cone can be difficult to advance in very hard cohesive soils such as glacial tills.
Good approach for design. Details in Section
FHWA
9-43

73. Tomlinson or α-Method Unit Shaft Resistance, fs: fs = ca = αcu Where:
ca = adhesion (Figure 9.18)
α = empirical adhesion factor (Figure 9.19)
9-42

74. Tomlinson or α-Method Shaft Resistance, Rs: Rs = fs As Where:
As = pile surface area in layer (pile perimeter x length)
H piles use “box” area – 4 sides, pg 45

75. Tomlinson or α-Method (SI)
9-43
Figure 9.18
Concrete, Timber, Corrugated Steel Piles
Smooth Steel Piles
b = Pile Diameter
D = distance from ground surface to bottom of clay layer or pile toe, whichever is less

76. Tomlinson or α-Method (US)
Figure 9.18
Concrete, Timber, Corrugated Steel Piles
Smooth Steel Piles
b = Pile Diameter
D = distance from ground surface to bottom of clay layer or pile toe, whichever is less

77. Tomlinson or α-Method
Sand or
Sandy Gravels D
Stiff Clay b

78. Tomlinson or α-Method (SI)
D = distance into stiff clay layer
b = Pile Diameter
Figure 9.19a
9-44

79. Tomlinson or α-Method (US)
D = distance into stiff clay layer
b = Pile Diameter
Figure 9.19b
9-48

80. Tomlinson or α-Method
Soft Clay D
Stiff Clay b

81. Tomlinson or α-Method (SI)
D = distance into stiff clay layer
b = Pile Diameter
Figure 9.19b
9-44

82. Tomlinson or α-Method (US)
D = distance into stiff clay layer
b = Pile Diameter
Figure 9.19b
9-48

83. Tomlinson or α-Method D
Stiff Clay b

84. Tomlinson or α-Method (SI)
D = distance into stiff clay layer
b = Pile Diameter
Figure 9.19c
9-44

85. Tomlinson or α-Method (US)
D = distance into stiff clay layer
9-48
b = Pile Diameter
Figure 9.19b

86. HIGHLY OVERCONSOLIDATED CLAYS
In highly overconsolidated clays, the undrained shear strength may exceed the upper limits of Figures 9.18 and 9.19.
In these cases, the adhesion factor should be calculated according to API procedures based on the ratio of the undrained shear strength of the soil, cu, divided by the effective overburden pressure, po’. The ratio of cu / po’ is .
For  ≤ 1.0, α = 0.5 -0.5
For  > 1.0, α = 0.5 -0.25

87. Tomlinson or α-Method Unit Toe Resistance, qt: qt = cu Nc Where:
cu = undrained shear strength of the soil at pile toe
Nc = dimensionless bearing capacity factor
(9 for deep foundations)

88. Tomlinson or α-Method Toe Resistance, Rt: Rt = qt At
The toe resistance in cohesive soils is sometimes ignored since the movement required to mobilize the toe resistance is several times greater than the movement required to mobilize the shaft resistance.

89. Tomlinson or α-Method
Ru = RS + RT
and
Qa = RU / FS

90. STUDENT EXERCISE #2
Use the α-Method described in Section a and the Nordlund Method described in Section c to calculate the ultimate pile capacity and the allowable design load for a inch O.D. closed end pipe pile driven into the soil profile described below. The trial pile length for the calculation is 63 feet below the bottom of pile cap excavation which extends 3 feet below grade. The pipe pile has a pile-soil surface area of 3.38 ft2/ft and a pile toe area of 0.89 ft2. Use Figure 9.18 to calculate the shaft resistance in the clay layer. The pile volume is 0.89 ft3/ft. The effective overburden at 56 feet, the midpoint of the pile shaft in the sand layer is 3.73 ksf, and the effective overburden pressure at the pile toe is 4.31 ksf. Remember, the soil strengths provided are unconfined compression test results (cu = qu / 2).

91. Soil Profile 3 ft Silty Clay = 127 lbs / ft3 qu = 5.46 ksf
Set-up Factor = 1.75
Dense, Silty F-M Sand
= 120 lbs / ft3
 = 35˚
Set-up Factor = 1.0
3 ft

92. Solution
We will discuss this solution during the DRIVEN workshop (ie steps 1-9)
STEP 10
Qu = Rs + Rt
= = 1875 kN

93. Calculate the Shaft Resistance in the Clay Layer Using α-Method
STEP 1 Delineate the soil profile and determine the pile adhesion from Figure 9.18.
Layer 1: qu = 260 kPa so cu =
D/b =
Therefore ca from Figure 9.18 =
130 kPa
14 m / 324 mm = 43

94. Tomlinson or α-Method (SI)70
9-45
Figure 9.18
Concrete, Timber, Corrugated Steel Piles
Smooth Steel Piles
b = Pile Diameter
D = distance from ground surface to bottom of clay layer or pile toe, whichever is less

95. Calculate the Shaft Resistance in the Clay Layer Using The α-Method
STEP 1 Delineate the soil profile and determine the pile adhesion from Figure 9.18.
Layer 1: qu = 260 kPa so cu =
D/b =
Therefore ca =
130 kPa
14 m / 324 mm = 43
70 kPa

96. Calculate the Shaft Resistance in the Clay Layer Using α-Method
STEP 2 Compute the unit shaft resistance, fs, for each soil layer.
STEP 3 Compute the shaft resistance in the clay layer.
Layer 1: Rs1 = ( fs1 )( As )( D1) =
Rs1 = (70 kPa)(1.02 m2/m)(13 m) = 928 kN

97. Calculate the Shaft Resistance in the Sand Layer Using the Nordlund Method
STEP 1 The po diagram, soil layer determination, and the soil friction angle, N, for each soil layer were presented in the problem introduction.
STEP 2 Determine *.
a. Compute volume of soil displaced per unit length of pile, V.
V = m3/m (per problem description)
b. Determine */N from Figure 9.10.
V = m3/m 6 */N = or * = N

98. Relationship Between Soil Displacement, V, and /
0.25
0.75
/ = 0.62
a – closed-end pipe and non-tapered Monotube piles
b – timber piles
c – pre-cast concrete piles
d – Raymond Step-Taper piles
e – Raymond uniform piles
f – H-piles
g – tapered portion of Monotube piles

99. Calculate the Shaft Resistance in the Sand Layer Using the Nordlund Method
STEP 1 The po diagram, soil layer determination, and the soil friction angle, , for each soil layer were presented in the problem introduction.
STEP 2 Determine *.
a. Compute volume of soil displaced per unit length of pile, V.
V = m3/m (per problem description)
b. Determine */N from Figure 9.10.
V = m3/m 6 */N = or * = N =
0.62
0.62
0.62 (35˚ ) = 21.7˚

100. Calculate the Shaft Resistance in the Sand Layer Using the Nordlund Method
STEP 3 Determine K* for each soil layer based on displaced volume, V, and pile taper angle, .
Layer 2: For  = 35˚, V = m3/m and  = 0˚
From Figure 9.13: K = for V = m3/m
K = for V = m3/m
Using log linear interpolation K = for V = m3/m
STEP 4 Determine correction factor, CF, to be applied to K when  ≠ . (Figure 9.15.)
Layer 2:  = 35˚ and / = CF =
0.62

101. Correction Factor for K when   
CF = 0.78
 = 35˚
Figure 9.15

102. Calculate the Shaft Resistance in the Sand Layer Using the Nordlund Method
STEP 3 Determine K* for each soil layer based on displaced volume, V, and pile taper angle, .
Layer 2: For  = 35˚, V = m3/m and  = 0˚
From Figure 9.13: K = for V = m3/m
K = for V = m3/m
Using log linear interpolation K = for V = m3/m
STEP 4 Determine correction factor, CF, to be applied to K when  ≠ .
Layer 2:  = 35˚ and / = CF =
0.62
0.78

103. Calculate the Shaft Resistance in the Sand Layer Using the Nordlund Method
STEP 5 Compute effective overburden pressure at midpoint of each soil layer, pd.
From problem description, pd for layer 2 is 177 kPa.
STEP 6 Compute the shaft resistance for each soil layer.
Rs2 = K CF pd sin  Cd D
= (1.72) (0.78) (177 kPa) (sin 21.7˚) (1.02 m2/m) (6m)
= 537 kN

104. Compute the Ultimate Shaft Resistance, Rs
Rs = Rs1 + Rs2
Rs = 928 kN kN
Rs = 1465 kN

105. Compute the Ultimate Toe Resistance, Rt
STEP 7 Determine αt coefficient and bearing capacity factor N'q from  angle of 35˚ at pile toe and Figures (a) and 9.16(b)
At pile toe depth D/b =
From Figure 9.16(a) αt =
From Figure 9.16(b) N'q =
20 / .324 = 62

106. αt Coefficient versus 
0.67 t
 = 35˚
 (degrees)
Figure 9.16a

107. Figure 9.16 Chart for Estimating αt Coefficient and Bearing Capacity Factor N'q (Chart modified from Bowles, 1977) 65
Figure 9.16b

108. Compute the Ultimate Toe Resistance, Rt
STEP 7 Determine αt coefficient and bearing capacity factor N'q from  angle of 35˚ at pile toe and Figures (a) and 9.16(b)
At pile toe depth D/b = 62
From Figure 9.16(a) αt = 0.67
From Figure 9.16(b) N'q = 65
STEP 8 Compute effective overburden pressure at pile toe.
pt =
150 kPa

109. Compute the Ultimate Toe Resistance, Rt
STEP 9 Compute the ultimate toe resistance, Rt.
a. Rt =αt N'q At pt
b. Rt = qL At (qL determined from Figure 9.17)
c. Use lesser value of Rt from Step 9a and 9b.
Therefore, Rt =
= (0.67)(65)(0.082 m2)(150 kPa) = 536 kN

110. Limiting Unit Toe Resistance – (SI)
5000
Figure 9.17

111. Compute the Ultimate Toe Resistance, Rt
STEP 9 Compute the ultimate toe resistance, Rt.
a. Rt =αt N'q At pt
b. Rt = qL At (qL determined from Figure 9.17)
c. Use lesser value of Rt from Step 9a and 9b.
Therefore, Rt =
= (0.67)(65)(0.082 m2)(150 kPa) = 536 kN
= (5000 kPa)(0.082 m2) = 410 kN
410 kN

112. Compute the Ultimate Pile Capacity, Qu
STEP 10
Qu = Rs + Rt
= = 1875 kN

113. DRIVEN COMPUTER PROGRAM
DRIVEN uses the FHWA recommended Nordlund (cohesionless) and α-methods (cohesive).
Can be used to calculate the static capacity of open and closed end pipe piles, H-piles, circular or square solid concrete piles, timber piles, and Monotube piles.
Analyses can be performed in SI or US units.
Available at:
9-53

114. DRIVEN COMPUTER PROGRAM
User inputs soil profile identifying soil statigraphy, soil type (cohesionless or cohesive), soil unit weight, soil strength parameters ( or cu) and percentage strength loss during driving.
Program analysis options include:
Soft compressible soils
Scourable soils
Pile plugging
9-53

115. DRIVEN COMPUTER PROGRAM
DRIVEN calculates the pile capacity at the time of driving using user input soil strength losses (Driving), the capacity after time dependent strength changes have occurred (Restrike), and the capacity after extreme events (Ultimate).
% Driving Strength Loss = 1 – [1 / setup factor]
DRIVEN generates soil input file for GRLWEAP wave equation program.
9-61

116. DRIVEN COMPUTER PROGRAM Student exercise #4

117. 9-58

118. 9-59

119. 9-59

120. 9-60

121. 9-60

122. Go To
Tabular Output
9-62

123. 9-62

124. Go To
Graphical Output
9-62

125. 1482 kN
9-63

126. 1877 kN
9-63

127. GRLWEAP Driveability Analysis File
Create
GRLWEAP Driveability Analysis File
9-62

128. NIM

129. PILES DRIVEN TO ROCK
The capacity of piles driven to rock should be based on driving observations, local experience, and load test results.
RQD values from NX size rock cores can provide a qualitative assessment of rock mass quality.
What is RQD?
RQD
Rock Mass Quality
90 – 100
Excellent
75 – 90
Good
50 – 75
Fair
25 – 50
Poor
0 - 25
Very Poor
9-54

130. PILES DRIVEN TO ROCK
Except for piles driven to soft rock, the structural capacity of the pile will be lower than the geotechnical capacity of the rock to support a toe bearing pile. (Fair to excellent quality rock).
The structural capacity of the pile (Chapter 10) then governs the pile capacity.
9-54

131. METHODS BASED ON CPT DATA
Pages 9-65 through 9-80
Nottingham and Schmertmann
Laboratoire des Ponts et Chaussees (LPC)
Elsami and Fellenius

132. UPLIFT CAPACITY OF SINGLE PILES pg 9-81
Increasingly important design consideration
Sources of uplift loads include seismic events, vessel impact, debris loading and cofferdam dewatering.
The design uplift load may be taken as 1/3 the ultimate shaft resistance from a static analysis.

133. UPLIFT CAPACITY OF SINGLE PILES
Undrained clays – uplift = compression
Drained sands - uplift < compression

134. UPLIFT CAPACITY OF SINGLE PILES
The design uplift load may be taken as 1/2 the ultimate tension load test failure load defined in Section of Chapter 19.
A reduction in the design uplift load may be necessary under cyclic or sustained loading conditions.
Clays – peak strength to a residual strength
Sands – particle degradation or reorientation

135. Lesson 7 – Learning Outcomes
You will be able to:
Identify the FHWA recommended static analysis methods in cohesionless and cohesive soils.
Calculate, by hand, the axial compression capacity of a single pile in cohesionless, cohesive, and layered soils.
Review that objective was achieved.

136. Lesson 7 – Learning Outcomes
You will be able to:
Determine when the axial compression capacity is controlled by the structural pile capacity.
Discuss the DRIVEN software for axial compression capacity calculations.
Review that objective was achieved.

137. Lesson 7 – Learning Outcomes
You will be able to:
Determine when the axial compression capacity is controlled by the structural pile capacity.
Discuss the DRIVEN and LPILE software for axial compression and lateral capacity calculations.
Locate 3 lateral pile capacity design methods.
Review that objective was achieved.

138. Any Questions

139. STATIC ANALYSIS – SINGLE PILES LATERAL CAPACITY METHODS
Reference Manual Chapter 9.7.3
9-82

140. Lateral Capacity of Single Piles
Potential sources of lateral loads include vehicle acceleration & braking, wind loads, wave loading, debris loading, ice forces, vessel impact, lateral earth pressures, slope movements, and seismic events.
These loads can be of the same magnitude as axial compression loads.
Review that objective was achieved.

141. Lateral Capacity of Single Piles
Historically, prescription values were used for lateral capacity of vertical piles, or battered (inclined) piles were added.
Modern design methods are readily available which allow load-deflection behavior to be rationally evaluated.
Review that objective was achieved.

142. Lateral Capacity of Single Piles
Soil, pile, and load parameters significantly affect lateral capacity.
Soil Parameters
Soil type & strength
Horizontal subgrade reaction
Pile Parameters
Pile properties
Pile head condition
Method of installation
Group action
Lateral Load Parameters
Static or Dynamic
Eccentricity
Review that objective was achieved.

143. Lateral Capacity of Single Piles
Design Methods
Lateral load tests
Analytical methods
Broms’ method, 9-86, (long pile, short pile)
Reese’s COM624P method
LPILE program
FB-PIER
Review that objective was achieved.
9-85

144. Review that objective was achieved.
Figure Soil Resistance to a Lateral Pile Load (adapted from Smith, 1989)
9-83

145. NIM

146. Figure 9.44 LPILE Pile-Soil Model
Review that objective was achieved.
Figure LPILE Pile-Soil Model
9-101

147. NIM

148. NIM

149. Review that objective was achieved.
Figure Typical p-y Curves for Ductile and Brittle Soil (after Coduto, 1994)
9-102

150. Behavior versus Depth (after Kyfor et al. 1992)
Review that objective was achieved.
Figure Comparison of Measured and COM624P Predicted Load-Deflection
Behavior versus Depth (after Kyfor et al. 1992)
9-93

151. Figure 9.48 LPILE Main Screen
Review that objective was achieved.
Figure LPILE Main Screen
9-106

152. 9-107

153. 9-107

154. 9-109

155. 9-111

156. 9-114

157. Integrate Differentiate
Review that objective was achieved.
Figure Graphical Presentation of LPILE Results (Reese, et al. 2000)
9-92

158. ANY QUESTIONS ?