Thermal Integrity Testing of Drilled Shafts

1. Thermal Integrity Testing of Drilled Shafts GMEC Conference April 30, 2009 Presented by: Gray Mullins, Ph.D., P.E.

2. Overview • Background • System Overview • New Modeling Developments • Hydration energy parameters • Soil temperature boundary conditions • Conclusions

3. Why Test Shaft Integrity? 1 - 4 & US 192

4. Why Test Shaft Integrity? 1 - 4 & SR 400

5. Why Test Shaft Integrity? 1 - 4 & SR 400

6. Thermal Integrity Testing System • Focused Infrared detectors (four per probe) • Depth encoded wheel • Computerized data acquisition • 3-D Signal matching program

7. Depth encoder Data acquisition Access Tubes Lead Wire to Infrared Probe

8. Single Shaft Heat Signature

9. Loss of Cover Necking in the shafts shows as lower than normal temperature.

10. Loss of Cover

11. CSL DOES NOT SHOW LOSS OF COVER

12. 3-D Image of Shaft underground with cover loss 2-D Thermograph of Shaft underground with cover loss

13. Sample Data

14. Over-pour / Bulging Excess concrete cover or bulging around the normal shaft shape shows as higher than normal temperature.

15. Measured Results Model Results Modeled Measured

16. Cage Misalignment An un-centered cage provides more cover on one side and less on the other. This shows as higher or lower than normal temperature as discussed earlier.

17. Cage Alignment

18. This part gets technical not for some audiences • We are good at predicting shaft shape underground due to very accurate concrete energy models • The next several slide discuss how energy is computed so we know how hot or cold a normal shaft should be.

19. Modeling Energy Production Cementitious composition Flyash composition Total cementitious concent Water cement ratio

20. Hydration Energy(Schindler, 2005) Cement Energy Production Total Energy Production

21. Hydration Energy(Schindler, 2005) Degree of Hydration Rate of Energy Production

22. Input Parameters(available from concrete supplier)

23. Normal shaft temp = 124F Shaft Size 42 inches Cast Shaft Test Shaft 28 hrs after casting Good Models Tell us what normal temperature should be

24. Ground Temperature Modeling MUST KNOW ORIGINAL GROUND TEMP Ground temperature not constant with depth Dependent on soil type, time of day, day of year, previous daily air temperature Long duration modeling used to condition the soil temperature boundary conditions

25. Historical Air Temperature(soil conditioning) Test Date

26. Daily Air Temperature(time of casting to testing) Time of Casting Time of Testing

27. February ‘08

28. March ‘08

29. April ‘08

30. May ‘08

31. June ‘08

32. July ‘08

33. September ’08 (hottest)

34. September ‘08

35. October ‘08

36. November ’08 (early)

37. November ’08 (cold snap)

38. December ‘08

39. January ‘09

40. Manual Soil Temperature Measurements Provide Model Calibration / Verification Modeled Cold Shaft Testing (4 year old test shaft)

41. Conclusions • Infra-red Thermal Integrity testing shows remarkable capability to detect anomalies outside the reinforcing cage (bulges, necks,) as well as misaligned cages • Advances in modeling energy production and soil temperature increase resolution of anomaly predictions.

42. 712 East Alsobrook Street, Suite 3  Plant City, FL 33563 Office: (813) 759-2426 Fax: (813) 759-2427  Email: engineering@foundations.cc Infrared Integrity Services available at http://foundations.cc/      Home         About FGE         Services           Projects           Contact