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

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

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

BACKGROUND GGL CHOSEN AS PRIMARY TEST CALIFORNIA TEST 233 SINCE 2005

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

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

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 49-3.02a(4)(D) ]

WHEN IS GGL REQUIRED?

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.

WHEN IS GGL REQUIRED? BCM 130-20 Att. No. 1.2

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.

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.

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

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

HOW DOES IT WORK?

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.

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

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.

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.

Interpreting results

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.

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

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

SYSTEM REQUIREMENTS

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 3.0” < Rd < 4.5” Density precision Pd< 1 lbs. / cu. ft.

Requirements of the system 1 3 2 4 5

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

Requirements of the system 1 3 2 4 5

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

Requirements of the system 1 3 2 4 5

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

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

Requirements of the system Rd 12:1 Slope Transition Zone

Requirements of the system 1 3 2 4 5

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)

Requirements of the operator

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.

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

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

LIMITATIONS OF GGL

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

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

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

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

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

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

Common reasons for test delays

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

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

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

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

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

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

Questions?

Obstructions to Pig

Obstructions to Pig

Broken Tremie Pipe

Cold Joints in CIDH Piles

Cold Joints in CIDH Piles

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