1. Lateral Statnamic Load Testing of Large Diameter Drilled Shafts and Piers
Deep Foundation Institute
Bay Area Rapid Force Pulse Seminar
Don Robertson, P.E. – Applied Foundation Testing

2. Lateral Set-up
Instrumentation
Concept of Lateral Statnamic Analysis
Results
Lateral Statnamic Load Testing of Large Diameter Drilled Shafts and Piers

3. Lateral Statnamic Load Testing Key Points
Capable of Loads Ranging From less than 100 kips to Over 3000 kips
Relatively Easy Setup – No Reaction Pile Required
Long load pulse width provides a good model of ship impact, earthquake, and other extreme event loads
Analysis method provides excellent correlation with static response
Has been done simultaneously with liquefied soils
Very flexible - Has been used on single drilled shafts, single piles, piers founded on pile groups, piers founded on drilled shafts, auger cast-in-place piles, and ship hull testing

6. Lateral Statnamic Setup
Hemispherical Bearing
LVDTs
Reference Beam H
Accelerometers
Lateral Sled
Strain Gages
Foundation
Downhole Accelerometers

7. Lateral Statnamic Setup
Same Concept and Theory as Axial
Reaction masses on sled (friction is used to stop sled)
Hemispherical bearing between shaft and piston to transfer load without restraining the test rotation and to reduce eccentricity

8. Lateral Statnamic Setup

9. Instrumentation Load Cell Strain Gages
LVDT opposite load point on ref. beam
Accelerometer on ref. beam
Accelerometers on shaft opp. Load point to measure lateral acceleration
String of 8 Downhole accelerometers in inclinometer casing embedded in shaft or foundation element
2,000 samples/sec recorded for 3+ sec. (longer duration to measure any shaft oscillations)

10. Instrumentation

11. Instrumentation

12. Instrumentation

13. Instrumentation

14. Analysis…Lateral
Double integration of Accel. and direct measurement of displacement from LVDT
Measure Statnamic lateral load with Load Cell
Back calculate LPILE model for design from initial soil parameters and adjusted to match observed load/deflection and deflection/depth response of shaft, pile or pier

15. Analysis…Lateral
Model Shaft using single degree of freedom, model includes
Non-linear static spring resistance
Inertia of the shaft rotating about a hinge pt.
Viscous Damping
FStatnamic=Finertia+Fdamping+FStatic
Finertia = inertial resistance from effective mass of foundation, includes some passive earth pressure wedge of surrounding soil
Fdamping=effective viscous damping resistance
Fstatic=effective static soil resistance

16. Results From Lateral Load Test

17. Results…Lateral Load Test
Four Cycles of increasing load applied to shaft

18. Results…Lateral Load Test
LVDT and integrated accelerometer data similar

19. Results…Lateral Load Test
Effective mass in calculations only top 16’, shaft yielded in bending about 9 feet below grade

20. Results…Lateral Load Test
Gage at 75’, clipped in tension, likely much higher

21. Results…Lateral Load Test
Soil criteria used to model test condition in LPILE

22. Results…Lateral Load Test
LPILE model yields much earlier than observed, conservative
Otherwise model captures shaft behavior well within general range

23. Results of Load Test Program
Use of Statnamic load testing results by the designers allow the reduction of significant amounts of the drilled shaft quantities for this project:
952 lf of drilled shaft excavation
634 Cubic yards of concrete
Total project savings on the order of $230,000.00
Future projects will benefit from these test results
Reduced quantities allowed for more efficient equipment setup during production drilled shaft installation (shorter holes = smaller equipment)

24. Results…Lateral Load Test
Four Cycles of increasing load applied to shaft

25. Results…Lateral Load Test
Top of shaft displacement

26. Results…Lateral Load Test
Downhole acceleration and displacement

27. Results…Lateral Load Test
Peak displacement for four load cycles

28. Results…Lateral Load Test
Strain measurements for four load cycles

29. Results…Lateral Load Test
Peak strain measurements for four load cycles

30. Results…Lateral Load Test
Initial shaft stiffness

31. Results…Lateral Load Test

32. Results…Lateral Load Test

33. Results…Lateral Load Test

34. Results…Lateral Load Test

36. Questions???

37. Applied Foundation Testing