Quality Control of Drilled Piles (Drilled Shafts, Bored Piles, Augercast piles) Garland Likins, P.E. Pile Dynamics, Inc. August 2015 2015, Pile Dynamics, Inc.
For a pile to successfully carry the required load it must have: good structural integrity adequate bearing capacity - we cannot afford failures -
Why Test?? How to test Structural Integrity Low Strain Integrity Testing Cross-hole Sonic Logging Calipers Thermal Integrity Profiling Q R? How to test Geotechnical Capacity Inspection devices Static Load Testing Bi-directional Load Testing Dynamic Load Testing
Structural Integrity Evaluations
Low Strain Integrity Testing ASTM D5882
Pile Preparation Remove fractured or contaminated concrete Grind a flat spot to attach accelerometer
Small hammer impact device Pile Integrity Testing (PIT) looks for major defects Accelerometer measures response (defect) 10
Free-End Free-Body Diagram Pile Forces Pile Velocities +F C T -F +v +v Equilibrium Continuity F=0 +2v
Basic Interpretation Good Pile Bad Pile
Low Strain Integrity Testing looks for major defects (PIT) PIT finds structural defect 350 mm CFA Static test failed to hold design load ( S.F. < 1 ) Failed static test prompts testing
Defect sometimes further down pile We excavated and I could stick my hand all the way to the middle of the pile and pull out handfuls of soil. 15
Classification of Results AA Good pile, clear toe ABx No defect to Depth x, no toe signal (long pile, high resistance, major bulges) PFx Probable Flaw at Depth x, toe apparent PDx Probable Defect at Depth x, no toe signal IVx Inconclusive below Depth x due to Vibrations (machinery, reinforcement) IR Inconclusive Record 17
Pile Profile in ideal conditions may estimate pile shape -0.04 0.00 0.04 0.08 in/s 0 0 5 5 10 10 15 15 20 20 25 25 30 30 x 2 40.00 ft (12700 ft/s) 35 40 45 35 40 45 50 50 55 55 60 Magn V 0.076 in/s (0.080) 60 ft diam
Tests : pile length 54 ft Testing pile in structure
Low Strain Integrity Testing Advantages Cost Effective even apply to all concrete piles Finds MAJOR defects Limitations / Disadvantages Limited to 30 to 50 L/D on concrete piles Difficult interpretation if highly non-uniform Cannot locate defect quadrant 20
Cross-hole Sonic Logging (CSL) ASTM D6760
Tubes (Perimeter & Major Diagonals) Tubes Paths Measurements required to define geometry 4 6 5 5 10 7 6 15 9 7 21 11 8 28 13 9 36 15 10 45 17 Detail required for good wavespeeds and tomography computed
Use an encoder (350 counts per rev.) Measure tube length Pull probe full length of tube Proportion counts to depth Depth calibration 24
Pull Probes From Bottom To Top Cross-hole Sonic Logging CSL Top view of shaft with 4 access tubes Fill Tubes with water Test all paths Transmit Receive 25
How to find defects? Good Defect 1. Reduced signal strength ( lower energy ) 2. Delayed FAT - First Arrival Time (low wavespeed)
Cross-hole Analyzer Signal Defect Arrival Arrival Defect Defect
Good/Satisfactory (G) FAT increase 0 to 10% and Energy Reduction < 6 db Questionable (Q) FAT increase 11 to 20% or Energy Reduction < 9 db Poor/Flaw (P/F) FAT increase 21 to 30% or Energy Reduction of 9 to 12 db Poor/Defect FAT increase >31% CSL rating guide (P/D) or Energy Reduction > 12 db
Repaired by pressure grouting 1 31
extracted shaft 32 32
CSL Tomography 1-2 Results should be compared with waterfall data. 33
ASTM D6760 suggests test after 3 days French norm requires 7 day wait 10 DAYS 13 DAYS
Initial test 30 min later Debonding Test after flooding top of shaft
Bleed water channel effect Know the situation of the test shaft
Canary Wharf Testing Pile 448 - large shell defect 41
Cross-hole Sonic Logging Advantages Access tubes inspire better construction Checks concrete inside cage by depth & quadrant Limitations / Disadvantages Wait 3 to 7 days prior to test Cannot evaluate concrete outside cage Debonding, bleeding are issues leads to unnecessary coring
Advantages Gamma Density Logging Gives data on concrete cover Compliments CSL testing Disadvantages Very local range (maybe 4 inch - 100 mm) near PVC tubes Radioactive materials
Advantages Calipers Estimates shape and volume required Measures verticality Limitations / Disadvantages Slurry sometimes obscures testing Assumes no further change before concreting
Thermal Integrity Profiling Use temperature vs. depth vs. quadrant Strength Shaft Serviceability Durability Cement Quantity Cover Concrete Temperature versus depth during curing at cage ASTM D7949
THERMAL WIRE cable Installation TAP Data Logger Thermal Wire
Thermal Wire cables installed in reinforcing cage
Shaft Heat Signature 80 Temperature 70 60 50 40 30 S46 S37 S28 20 S19 1 4 7 10 13 16 19 22 25 28 31 4 7 0S1 S10 59
Shaft Heat Signature 80 Temperature 70 60 50 40 30 S46 S37 S28 20 S19 1 4 7 10 13 16 19 22 25 28 31 4 7 0S1 S10
8.4 ft 8 ft 17 ft 17 ft 16.1 ft
Temperature roll-off in top and bottom one 1 63
End Effect Correction 80 Temperature (F) 70 80 90 100 110 120 130 140 85 90 avg toe tanh Depth (ft) 95 100 105 110
Method Shaft Temperature (deg F) No Correction for Over-pour Concrete 70 90 110 130 150 0 10 20 30 Average Grnd Surf TOS WT 40 BOC Depth (ft) 50 60 70 80 90 100 TOLime TOR BOS Effective Diam. Theoretical Diam. Truck volume and depth after each truck can establish the effective diameter for each shaft segment. 0 2 4 6 8 10 Shaft Diam (ft) No Correction for Tremie filling / volume
Method Shaft Temperature (deg F) No Correction for Over-pour Concrete 70 90 110 130 150 0 10 20 30 Average Grnd Surf TOS WT 40 BOC Depth (ft) 50 60 TOLime TOR 70 80 90 BOS Effective Diam. Theoretical Diam. Average temperature is related to average radius 100 0 2 4 6 8 10 Shaft Diam (ft) No Correction for Tremie filling / volume
March 2012 drilling Cleveland Shaft 3 66 inch shaft (R = 33 in) cage (R = 27 in) 180 ft length Volume Theoretical Actual 158 cu yd 191 cu yd (121%) Temp casing 84 inch dia. (R = 42 in) 28 ft length attach Thermal cables
TIP can look outside cage also and estimate the shaft profile
Iowa test shaft August 2014 Concrete prisms 5% of X-section Clay spoils 7% of X-section Tube 6 1.83 m (72 inch) nominal diameter
Optimum time to see defects Iowa test shaft Top 15 ft 78 Rest is 72 6 6 Cage alignment 11:12 hrs 19:33hrs Peak temperature
South Carolina test shaft - Sept 2014 Defects planned at Depth below top 4 ft (soil bags 15% of section) 21 ft (soil bags 15% of section) 58 66 Dia. 1.68 m dia. 1 44.5 60 Dia. 1.52 m dia. 5 SC DOT Sumpter SC
South Carolina test shaft
16 hours after end of pour clearly see planned defects 5 & 1 5 & 1 South Carolina test shaft
16 hours after end of pour also see unplanned defect! 4 South Carolina test shaft
About 34 hours after end of pour Max temperature 58 66 Dia. 44.5 60 Dia. South Carolina test shaft
4 ft dia shafts Michigan 4.5 dia bad good 4 83
11.5 Hours 25 Hours (Peak) 48 Hours Center West near cage Defect found best at early time 350 shafts tested by TIP in SC 6 shafts found with defects near top 1.22 m shaft (48 inch)
22 inch augercast x 16 ft depth