2. Discussion topics Background When is ggl required? How does it work?
Interpreting results
System requirements
Operator requirements
Limitations of the test
Frequent reasons for test delays

3. BACKGROUND Caltrans early 1990’s
INCREASED USE OF SLURRY DISPLACEMENT METHOD OF CIDH CONSTRUCTION
METHOD Required a NON-DESTRUCTIVE INTEGRITY test for quality assurance OF CONCRETE PLACEMENT

4. BACKGROUND
TEST WOULD measure a characteristic of in-place concrete to assess PILE integrity
OPTIONS INCLUDED SONIC ECHO, CROSSHOLE SONIC LOGGING AND GAMMA-GAMMA LOGGING

5. BACKGROUND
GGL CHOSEN AS PRIMARY TEST
CALIFORNIA TEST 233 SINCE 2005

6. BACKGROUND Advantages of ggl method
DEEP ANOMALIES NOT MASKED BY SHALLOW ANOMALIES
NO LIMITATION WHEN TEST NEEDS TO OCCUR
PVC PIPES INEXPENSIVE AND READILY AVAILABLE
NOT AFFECTED BY DEBONDING
EXPEDIENT TESTING AND ANALYSIS
HIGHLY REPEATABLE RESULTS
3 CALTRANS FTB LOGS FROM SAME PIPE

7. BACKGROUND Advantages of ggl method HIGHLY REPEATABLE RESULTS
Private Tester
Caltrans FTB

8. BACKGROUND
TWO METHODS FOR PILE ACCEPTANCE IN THE STANDARD SPECIFICATIONS
GGL PRIMARY AND CORING SECONDARY
CORING FOR CASES OF BLOCKED OR MISSING INSPECTION PIPES
CSL TO FURTHER EVALUATE REJECTED PILES
REFER TO [ Ss a(4)(D) ]

9. WHEN IS GGL REQUIRED?

10. WHEN IS GGL REQUIRED? ACCEPTANCE TESTING APPLIES TO ALL PILES, except:
TWO EXCEPTIONS:
PILES LESS THAN 24 INCHES IN DIAMETER
PILES CONSTRUCTED IN:
DRY HOLES, OR …
HOLES DEWATERED WITHOUT USE OF TEMPORARY CASING TO CONTROL GROUND WATER.

11. WHEN IS GGL REQUIRED?
BCM Att. No. 1.2

12. GGL NOT REQUIRED! DRY HOLE DEWATERED HOLE DRY PLACEMENT REQUIRES:
No work to achieve < 3” water across bottom at pour time
DEWATERED HOLE
DRY PLACEMENT REQUIRES:
< 3” WATER ACROSS BOTTOM
< 12” PER HOUR
Typically firm soils and lower groundwater table.
Drilled hole is generally stable and bottom of hole and concrete placement can be visually inspected from working grade.
Likelihood of defects is low.

13. GGL REQUIRED! WET HOLE, OR… ‘SLURRY Displacement’ method 10’
Typically unstable soils and/or high groundwater table.
Require placement under slurry by tremie.
Excavation of the hole and placement of reinforcing all occur under slurry. Following flocculation of suspended solids, bottom cleaning and/or recirculation of drill slurry, full length tremie pipe placed to bottom of hole. Concrete is deposited at the bottom of the hole and slurry is displaced at the top in a process referred to as “slurry displacement”. The tremie is slowly raised during placement while the bottom of tremie is maintained a minimum of 10’ into the concrete keeping what is referred to a the “tremie seal”.
Risk that drilled hole can collapse during reinforcement or concrete placement.
Added risk of contamination or degradation of concrete from mixing with drill slurry or loss of tremie seal.
Poor bottom cleaning prior to concrete placement.
Excessive sediment load in drill fluid column settles out during concrete placement.
Intermixing between drill fluid and concrete within the tremie pipe (leaking tremie or insufficient barrier or ‘pig’).
Loss of tremie seal either through raising bottom of tremie above concrete or parting the tremie pipe.
Concrete material properties not producing a fluid mix with delayed set that readily displaces slurry and maintains adequate pressure against walls of shaft.
Interruption to concrete placement and stiffening of concrete within the hole.
Failure to discharge sufficient concrete volume at end of pour to purge deleterious concrete carried at top of column.

14. GGL REQUIRED! SLURRY DISPLACEMENT and…
TEMPORARY CASING extending BELOW GROUNDWATER

15. GGL REQUIRED! Dewatered hole Temporary casing below groundwater
Condition most likely to result in failure to include inspection pipes

16. HOW DOES IT WORK?

17. HOW DOES IT WORK? 2 INCH ID Pvc inspection pipes
attached TO HOOPS OR SPIRALS
Number and spacing per plans
AT TIME OF TEST:
PIPES COMPLETELY dry, or..
completely filled with water
3 inches clear of vertical rebar
At a spacing not to exceed 33”
GGL is a homogeneity test so important to maintain constant influence of steel reinforcement.
Maintain vertical alignment so radioactive tool passes freely through length of pipe and during initial sounding with dummy probe.

18. HOW DOES IT WORK? Gamma-Gamma Probe Cable and Winch with depth encoder
1” Diameter Rigid Cylinder
Cesium 137 Source 3” From Tip
Gamma Particle Detector 15” Above Source
Cable and Winch with depth encoder
Readout / record Device (Laptop)
Gamma Count rate, Density, Sample Time

19. HOW DOES IT WORK? count rate calibrated to density
Calibrated using manufactured concrete blocks
Radiation emitted from the source in all directions. A shield within the probe between the source and detector prevents direct transmission. Radiation is simultaneously absorbed and backscattered by the concrete and steel surrounding the inspection pipe.

20. HOW DOES IT WORK? Density reading Logging rate measurement Location
every 0.1 foot
up or down direction
Logging rate
15 feet per minute.
measurement Location
mid-point between source-detector.
Source and Detector located within the same probe. Not a direct transmission method. That would require too large a radioactive source.
Backscatter method. Radiation emitted from the source in all directions. A shield within the probe between the source and detector prevents direct transmission.
Radiation is simultaneously absorbed and backscattered by the concrete and steel surrounding the inspection pipe. Gamma particles reflected back to the detector are counted over an interval of time.
Denser material surrounding return a lower count. Inverse relationship between count rate and density.

21. Interpreting results

22. Interpreting results
determination of anomalies based on established statistical methods
affected pile cross-section based on representative sample
Established statistical methods for the determination of anomalies.
Concrete within a drilled shaft is homogeneous on a bulk scale that we can apply a normal distribution to density readings.
Based loosely on X-Control Charts.
Likelihood of two consecutive density readings beyond 3 standard deviation is statistically very low unless outside factor contributes to the measured value.
Research indicates a 0.05% chance exiss of two consecutive points indicating density lower than 2 standard deviations below the mean.

23. Interpreting results Mean density for each inspection pipe
Excluding anomalous DATA and top 1’
SEPARATE MEANS FOR change in horizontal reinforcing schedule
Each data reading subtracted from mean
Plot variation from mean for each inspection pipe

24. Interpreting results Standard deviation for data set
All pipes Excluding anomalous sections
Plot 3rd standard deviation
Identify ANOMALY
0.5’ consecutive readings below the mean minus 3 standard deviation line
Compare anomalies to construction records!
Coupler logs
Assign area to anomaly
May Recommend additional testing

25. SYSTEM REQUIREMENTS

26. Requirements of the system
5 MAIN SYSTEM REQUIREMENTS SPECIFIED IN CT 233:
QUALIFIED STANDARD REFERENCE BLOCK
Established functionality limits
Calibration to density
Radius of detection ” < Rd < 4.5”
Density precision Pd< 1 lbs. / cu. ft.

27. Requirements of the system1 3 2 4 5

28. Requirements of the system
QUALIFIED STANDARD REFERENCE BLOCK
FUNCTIONALITY LIMITS
LOWER-UPPER FUNCTIONALITY LIMITS (LFL-UFL)
LFL-UFL DETERMINED ANNUALLY (decay)
Daily functionality evaluation, per site

29. Requirements of the system1 3 2 4 5

30. Requirements of the system
CALIBRATION
measure gamma count rate (cps)
count rate calibrated to density
Calibrated against density barrels
Wet and dry calibration
Calibration determined annually
195.0
147.5
115.1
Density (lbs. / cubic foot)
Concrete Calibration Samples Located at Translab

31. Requirements of the system1 3 2 4 5

32. Requirements of the system
Radius of Detection, rd
3.0” < Rd < 4.5”
Verified every 4 years
Radius of Detection
Vertical Reinforcing
Inspection Pipe

33. Requirements of the system
2” PVC Pipe
Lightweight Concrete
Normal Weight Concrete
12:1 Transition Slope
Influence Determination Unit (IDU) for determining Radius of Detection of GGL Probe

34. Requirements of the systemRd
12:1 Slope
Transition Zone

35. Requirements of the system1 3 2 4 5

36. Requirements of the system
Random scatter due to variability of gamma emission and detector response.
METHOD TO VERIFY random scatter of GGL data is small compared to anomaly CRITERIA.
CT 233 establishes a minimum level of precision FOR GIVEN SAMPLE TIME (DENSITY PRECISION)
Density Precision < 1.0 lbs/cu. ft. at Max. 4 year
Less PRECISION WITH ENERGY DECLINE (DECAY) AND smaller SAMPLE TIMEs (HIGHER PROBE SPEED)

37. Requirements of the operator

38. Requirements of the operator
Testing organization must be an approved lab
approval by Caltrans Independent Assurance Program (IAP).
includes Private companies testing on Caltrans project.

39. Requirements of the operator
GGL OPERATOR MUST BE certified TO PERFORM CT 233 parts 1 to 4
Certified by Caltrans Independent Assurance Program (IAP).
Annual certification
Includes ggl operators working for private companies
Tester

40. Requirements of the operator
Analysis and report by a civil engineer registered in the state of California
Requirement of ct 233

41. LIMITATIONS OF GGL

42. LIMITATIONS OF GGL RADIUS OF DETECTION
Readings skewed across ~top 1 foot (unless over-poured)
No readings for ~bottom 1 foot of inspection pipe
No readings below inspection pipe

43. Limitations of the method
RADIUS OF DETECTION
READINGS APPROXIMATELY 3” beyond inspection pipe
7% of cross-section evaluated by GGL for a 6’ diameter pile
Evaluating both inside and outside of pile reinforcing
Radius of Detection
Vertical Reinforcing
Inspection Pipe

44. Limitations of the method
Compared to CROSSHOLE SONIC LOGGING (CSL)
70% of cross-section evaluated by csl for a 6’ diameter pile.
Limited to inside pile reinforcing
Combined ggl-csl complements each test
Radius of Detection
Vertical Reinforcing
Inspection Pipe

45. Limitations of the method
Limitations at pile top and bottom
View the Idu as a 19 foot pile
Probe source at end (bottom) of pile
Probe exits in a similar boundary condition

46. Limitations of the method
TOP 1’ OF PILE
READINGS SKEWED AS DETECTOR APPROACHES TOP OF PILE
EFFECT CHANGES WITH BOUNDARY CONDITION

47. Limitations of the method
BOTTOM 1’ OF INSPECTION PIPE
SOURCE LOCATED ~3.5” ABOVE TIP OF PROBE
SOURCE-DETECTOR SPACING, 15”
1ST READING MID DISTANCE BETWEEN SOURCE AND DETECTOR
NO READINGS BELOW INSPECTION PIPE

48. Common reasons for test delays

49. frequent reasons for test delays
NO EXCLUSION ZONE
BLOCKED INSPECTION PIPES
PARTIALLY FILLED INSPECTION PIPES
ACCESS to inspection pipes
PIPES NOT PLACED CORRECTLY

50. frequent reasons for test delays
EXCLUSION ZONE around radioactive source
construction activities within 25 feet of radioactive source

51. frequent reasons for test delays
BLOCKED INSPECTION PIPES
ACCEPTANCE TESTING CANNOT BE COMPLETED
Risk of losing the radioactive source.
Year 2015
1,351 inspection pipes tested
7 INSPECTION PIPES BLOCKED

52. frequent reasons for test delays
PARTIALLY FILLED INSPECTION PIPES
CT 233 ANALYSIS CANNOT BE APPLIED TO DATA COLLECTED AS PROBE TRANSITIONS FROM WATER TO AIR

53. frequent reasons for test delays
ACCESS TO INSPECTION PIPES
SEPARATING REINFORCING ON TYPE 1 SHAFTS
SAFETY CONCERNS
GGL OPERATOR CARRYING PROBE UP LADDER OR CAGE
PRINCIPLE OF ALARA

54. frequent reasons for test delays
PIPES missing or NOT PLACED CORRECTLY
Extended review time by designers
Possible coring

55. Questions?

56. Obstructions to Pig

57. Obstructions to Pig

58. Broken Tremie Pipe

59. Cold Joints in CIDH Piles

60. Cold Joints in CIDH Piles

61. HOW DOES IT WORK? DIFFERENT FROM crosshole sonic logging (csL)
Csl uses a transmitter and receiver to evaluate pile concrete
MEASURES SONIC WAVE arrival time and energy
Csl Not A CALTRANS acceptance test
Access Tubes
Cast into Shaft
Read-out Unit
12,500 fps
Transmitter
Receiver
Sound Wave
Crosshole Sonic Transmitter / Receiver