What is Pile Integrity Test ?

This slideshare provides geotechnical engineers and nondestructive testing professional with information on low strain impact integrity testing of deep foundations and piles.

1. A quick review of low strain impact tests for deep foundations What is Pile Integrity?

2. In This Video What is Pile Integrity How To Evaluate Pile Integrity Low Strain Impact Integrity Test Practical Considerations Analysis and Reporting 2

3. “Pile integrity is the qualitative evaluation of the physical dimensions, continuity of a pile, and consistency of the pile material.” 3

4. Why do we need to test? 4

5. Sound pile Major Defect Bulging Necking

6. How to Evaluate Pile Integrity The theory behind the low strain impact integrity test 6

7. Low Strain Impact Integrity Test – ASTM D 5882 High Strain Dynamic Testing – ASTM D 4945 Crosshole Sonic Logging – ASTM D 6760 Parallel Seismic Method Thermal Integrity Profiling – ASTM D7949 7 Methods for Testing

8. The Sonic-Echo Method 8 Low Strain Impact Integrity Test

9. The Test in a Nutshell Evaluate integrity of deep foundation by “measuring and analyzing the velocity response of the pile induced by an impact device usually applied axially and perpendicularly to the pile head surface.” Motion transducer        

10. What tools are needed for testing? Hammer Motion Transducer Velocity or acceleration sensor Data Recording Unit Motion transducer Materials Needed

11. How it Works

12. Motion transducer   Time                     The Theory

13. Evaluate integrity and consistency of pile material Evaluate unknown length of piles or shafts Evaluate pile cross-sectional area and length 13 Applications

14. Pile preparation is relatively easy The process of testing and data collection is rapid and inexpensive PIT can identify major defects 14 Advantages

15. Can not be used to determine the load bearing capacity of piles Interpretation of test results need experience Can’t be conducted over the pile cap Sensitive length (L) to pile diameter (D) ratio. Piles with highly variable cross-section or multiple discontinuities/anomalies may be difficult to evaluate 15 Disadvantages

16. Practical Considerations Some things to consider when testing. 16

17. You can test 7 days after casting or after concrete achieve 75% of its design strength. 17 Timing

18. Make sure the pile head is: Accessible, Above water, Clean of loose concrete, or soil 18 Surface Preparation

19. You will need bonding material to attach the motion transducer. Use a thin layer wax, petroleum jelly, or putty. 19 Bonding material Bonding Material

20. 20 Pile Diameter < 500 mm Pile Diameter > 500 mm Place sensor at center Place sensor at 3 different locations Pile Placement Location of impacts

21. 21 300 mm Impactor Distance

22. 22 90° Motion Transducer Position When testing, ensure that The device is perpendicular to the pile axis The impacts are applied parallel to the motion transducer

23. If individual impacts are recorded, collect at least 10 impacts per pile; Rule of thumb: perform 3 blows and use the average for each record. General: The more hammer blows recorded, the greater reduction in the effects of random noise. The background noise can be reduced by a factor of √n , where n is the number of superimposed signals from the same pile. 23 Number of Records

24. Light Hammer Use for piles less than 1 m Less than 1kg Heavy Hammer Use for larger piles, more than 1m in diameter Should be 1.5 – 6 Kg Type of Hammer

25. Data Analysis Some things to consider when testing. 25

26. 26 Bottom echo impulse Pile Integrity Test Record

27. 27 Motion Transducers collect acceleration or velocity induced by arriving echoes from the impact to the pile head If an acceleration transducer is used, measurements should be integrated and displayed in velocity format Given the stress wave speed, the time stamp, or horizontal axis can be converted to depth Pile Integrity Test Record

28. Operators shall monitor the velocity from several impact events for consistency. Do not use the records of impacts that cause the measurement device to overload (saturated signal with flat tip). Results should be repeatable. If they are not repeatable, do not use the data. Check sensor placement and attachment to pile head. 28 Data Quality Check

29. Stress wave speed depends on the quality of pile material. Stress wave speed in concrete is approximately 3,600 m/s (medium strength) to 4,400 m/s (high quality). In most cases, 4,000 m/s (13,000 ft/s) is a good first guess. 29 Stress Wave Speed

30. Filtering minimizes noise caused by: High frequency reflections from boundary High frequency noise from sudden or sharp changes in cross section High frequency noise induced by careless hammer blow A Low Pass filter can be used to reduce/remove the effect of high frequency noise 30 Filtering

31. Amplification is used to amplify low energy echoes. An exponential amplification function is applied to amplify the reflections from pile toe or defects in deep depths Low Pass filter can be used to reduce/remove the effect of high frequency noise.   31 Amplification function Amplification

32.   Sound Pile Pile with Defect

33. 33 toe toe Potential defect The Good, The Bad, & …

34. Concrete strength (samples/cores) Record pile diameter Initial estimation of pile length Initial estimation of wave speed in concrete Soil profile (soil stratigraphy) Construction record, observation 34 Other Information to Record

35. Email: [email protected] Tel: [phone] For more information: www.fprimec.com/ipile FPrimeC Solutions Inc. 300 – 2 Simcoe St. S. Oshawa, ON, L1H 8C1 35 Have Questions ?