1. Soil-Pile Interaction in FB-MultiPier
Dr. J. Brian Anderson, P.E.
Developed by: Florida Bridge Software Institute
Dr. Mike McVay, Dr. Marc Hoit, Dr. Mark Williams

2. Session Outline Identify and Discuss Soil-Pile Interaction Models
Precast & Cast Insitu Axial T-Z & Q-Z Models
Torsional T- Models
Lateral P-Y Models
Nonlinear Pile Structural Models
FB-MultiPier Input and Output
Example #1 Single Pile

3. Session Outline Identify and Discuss Soil-Pile Interaction Models
Precast & Cast Insitu Axial T-Z & Q-Z Models
Torsional T- Models
Lateral P-Y Models
Nonlinear Pile Structural Models
FB-MultiPier Input and Output
Example #1 Single Pile

4. Soil-Structure Interaction
Vertical Nonlinear Spring
Torsional Nonlinear Spring
Lateral Nonlinear Spring
Nonlinear Tip Spring

5. Driven Piles - Axial Side Modelz r  to
(Randolph & Wroth) d z s q r + D / t dr s

6. Driven Piles - Axial Side Modelrm
Also: Z z
Substitute: r
Rearrange:
Previous
Substitute:
Also:
Substitute:

7. Driven Piles - Axial Side Model
f = 1000psf
Gi = 3 ksi

8. Driven Piles - Axial Tip Model
(Kraft, Wroth, etc.)
Where:
P = Mobilized Base Load
Pf = Failure Tip Load
ro = effective pile radius
 = Poisson ratio of Soil
Gi = Shear Modulus of Soil
Pf = 250 kips
Gi = 10 ksi
 = 0.3
r0 = 12 inches

9. Driven Piles - Axial Properties
Ultimate Skin Friction (stress), Tauf , along side of pile (input in layers).
Ultimate Tip Resistance (Force), Pf , at pile tip .
Compressibility of individual soil layers, I.e. Shear Modulus, Gi , and Poisson’s ratio, n .

10. Driven Piles - Axial Properties
From Insitu Data:
Using SPT “N” Values run SPT97, DRIVEN, UNIPILE, etc. to Obtain: Tauf , and Pf
Using Electric Cone Data run PL-AID, LPC, FHWA etc. to Obtain: Tauf , and Pf
Determine G or E from SPT correlations, i.e. Mayne, O’Neill, etc.

11. Florida: SPT 97 Concrete Piles
Skin Friction, tf (TSF)
Plastic Clay:
f= 2N(110-N)/4006
Sand, Silt Clay Mix:
f = 2N(110-N)/4583
Clean Sand:
f = 0.019N
Soft Limestone
f = 0.01N
Ultimate Tip, Pf/Area(tsf)
Plastic Clay:
q = 0.7 N
Sand, Silt Clay Mix:
q = 1.6 N
Clean Sand:
q = 3.2 N
Soft Limestone
q = 3.6 N

12. Cast Insitu Axial Side and Tip Models
For soil (sands and clays)
Follow FHWA Drilled Shaft Manual For Sands and Clays to Obtain Tauf and Pf (g and cu)
Shape of T-Z cuve is given by FHWA’s Trend Lines.
User has Option of inputting custom T-z / Q-z curves

13. Cast Insitu - Sand (FHWA):
L/2
sv’ = g L/2 L
b = (L/2) > b >0.25 D
Qs = p D L b sv’
Qt = 0.6 NSPT p D 2 / NSPT < 75

14. Cast Insitu - Clay (FHWA):
Qs = 0.55 Cu p D (L-5’-D) L D
Qt = 6 [1+0.2(L/D) ] Cu (p D 2 / 4)

15. Cast Insitu trend line for Sand

16. Cast Insitu trend line for Clay

17. Session Outline Identify and Discuss Soil-Pile Interaction Models
Precast & Cast Insitu Axial T-Z & Q-Z Models
Torsional T- Models
Lateral P-Y Models
Nonlinear Pile Structural Models
FB-MultiPier Input and Output
Example #1 Single Pile

18. Torsional Model (Pile/Shaft)
Hyperbolic Model
G and Tauf
Custom T-q

19. Torsional Model (Pile/Shaft)
T (F-L)
(dT/dq)=1/a  Gi
Tult =1/b
Tult = f Asurf r
Tult = 2p r2 D L tult
ult = Ultimate Axial
Skin Friction
(stress)
T = q / ( a + b q )
q (rad)

20. Session Outline Identify and Discuss Soil-Pile Interaction Models
Precast & Cast Insitu Axial T-Z & Q-Z Models
Torsional T- Models
Lateral P-Y Models
Nonlinear Pile Structural Models
FB-MultiPier Input and Output
Example #1 Single Pile

21. Lateral Soil-Structure InteractionY
Active State
Passive State

22. Near Field: Lateral (Piles/Shafts)

23. P-y Curves - Reese’s Sand
Pu is a function of
, , and b k m
b/60
3b/80
x = 0
x = x1
x = x2
x = x3
x = x4 u p y yu P
ks x
Y is a function of b (pile diameter)

24. Matlock’s Soft Clay Pu is a function of Cu, , and b
Y is a function of
y50 (50)

25. Reese’s Stiff Clay Below Water
Pc is a function of
C, , ks and b
Y is a function of
y50 (50)

26. O’Neill’s Integrated Clay
Pu is a function of
c, and b
Fs is a function of 100
Yc is a function of b and 50

27. Soil Properties for Standard Curves
Sand:
Angle of internal friction, f
Total unit weight, g
Modulus of Subgrade Reaction, k
Clay or Rock:
Undrained Strength, Cu
Total Unit Weight, g
Strain at 50% of Failure Stress, e50
Optional: k, and e100

28. Soil Information
Help Menu
EPRI (Kulhawy & Mayne)

29. P-y Curves from Insitu Tests
Cone Pressuremeter
Marchetti Dilatometer

30. Insitu PMT & DMT Testing

31. Cone Pressuremeter

32. (Robertson, Briaud, etc.)
Cone Pressuremeter
(Robertson, Briaud, etc.)

33. Marchetti Dilatometer

34. PMT P-y Curves - Auburn

35. DMT P-y Curves - Auburn

36. Auburn Predictions

37. PMT P-y Curves Pascagoula

38. DMT P-y Curves Pascagoula

39. Pascagoula Predictions
500
1000
1500
2000
2500
3000
3500
4000
4500 10 20 30 40 50
Deflection (mm)
Load (kN)
DMT
PMT
Actual

40. Instrumentation & Measurements
Strain gages
Measure strain
Calculate bending moment, M = ε(EI/c), if EI of section known
“high tech”
Slope inclinometer
Measures slope
Relatively “low tech”

41. Theoretical Pile Behavior

42. Strain Gages  Bending Moment

43. Bending Moment versus Depth

44. Bending Moment vs. Depth

45. Two Integrals to Deflection

46. Two Derivatives to Load

47. Non-linear Concrete Model

48. P-y Curves from Strain Gages

49. Slope Inclinometer  Slope

50. Deflection versus Depth

51. Slope Inclinometer → Slope vs. Depth

52. One Integral to Deflection

53. Three Derivatives to Load

54. P-y Curves from Slope Inclinometer

55. Comparison of P-y Curves

56. Prediction of Pile Top Deflection

57. P-y Curves Available in FB-Pier
Standard
Sand
O’Neill
Reese, Cox, & Koop
Clay
Matlock Soft Clay Below Water Table
Reese Stiff Clay Below Water Table
Reese & Welch Stiff Clay Above Water Table

58. P-y Curves Available in FB-Pier
User Defined
Pressuremeter
Dilatometer
Instrumentation
Strain Gages
Slope Inclinometer

59. Session Outline Identify and Discuss Soil-Pile Interaction Models
Precast & Cast Insitu Axial T-Z & Q-Z Models
Torsional T- Models
Lateral P-Y Models
Nonlinear Pile Structural Models
FB-MultiPier Input and Output
Example #1 Single Pile

60. Pile Discrete Element Model

61. Curvature-Strain-Stress-Moment

62. Stress-Strain Curves for Concrete & Steel

63. Strains -> Stress -> Moments
dFi=si*dAi

64. Stiffness of Cross-Section: Flexure, AxialM q

65. Failure Ratio Calculation
Actual Length P
Failure Ratio =
Surface Length Mx
Pactual
Mxo My
Myo

66. Pile Material Properties

67. References:
Robertson, P. K., Campanella, R. G., Brown, P. T., Grof, I., and Hughes, J. M., "Design of Axially and Laterally Loaded Piles Using In Situ Tests: A Case History,“ Canadian Geotechnical Journal, Vol. 22, No. 4, pp , 1985.
Robertson, P. K., Davies, M. P., and Campanella, R. G., "Design of Laterally Loaded Driven Piles Using the Flat Dilatometer," Geotechnical Testing Journal, GTJODJ, Vol. 12, No. 1, pp , March 1989.
Reese, L. C., Cox, W. R. and Koop, F. D (1974). "Analysis of Laterally Loaded Piles in Sand," Paper No. OTC 2080, Proceedings, Fifth Annual Offshore Technology Conference, Houston, Texas, (GESA Report No. D-75-9).
Hoit, M.I, McVay, M., Hays, C., Andrade, P. (1996). “Nonlinear Pile Foundation Analysis Using Florida Pier." Journal of Bridge Engineering. ASCE. Vol. 1, No. 4, pp
Randolph, M. and Wroth, C., 1978, “Analysis of Deformation of Vertically Loaded Piles, ASCE Journal of Geotechnical Engineering, Vol. 104, No. 12, pp
Matlock, H., and Reese, L., 1960, “Generalized Solutions for Laterally Loaded Piles,” ASCE, Journal of Soil Mechanics and Foundations Division, Vol. 86, No. SM5, pp

68. Session Outline Identify and Discuss Soil-Pile Interaction Models
Precast & Cast Insitu Axial T-Z & Q-Z Models
Torsional T- Models
Lateral P-Y Models
Nonlinear Pile Structural Models
FB-MultiPier Input and Output
Example #1 Single Pile