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Non-Destructive Evaluation of a Deep Foundation Test Section at the
Northwestern University National Geotechnical Experimentation Site
A Report Submitted to the Federal Highway Administration
Dr. Richard J. Finno
Sarah L. Gassman
Peter W. Osborn
Northwestern University
Evanston, Illinois
June 1997
List of Figures Figure 2.1. Wavefronts of Compression, Shear and Rayleigh Waves Produced by a Point Impact on a Surface.
Figure 2.2. Theoretical Variation of the Two Compression-Wave Velocities and the Shear-Wave Velocity with Confining Pressure, as Calculated from the Biot (1956) Theory (from Hardin, 1961), (after Richart et. al., 1970).
Figure 2.3. Force-Time Function of Elastic Impact of a Sphere on a Solid (after Sansalone and Carino, 1986)
Figure 2.4. Frequency Spectrum of Force-Time Function (after Sansalone and Carino, 1986)
Figure 2.5. Reflection and Transmission of a Stress Wave at an Impedance Change
Figure 2.6. Reflection and Refraction of an Incident Compression Wave at an Interface
Figure 2.7. Mode Conversion of an Incident Compression Wave at an Interface
Figure 2.8. Testing Setup for Surface Reflection Techniques: Accessible-Head and Inaccessible Head
Figure 2.9. Response Curve for SM-6 Digital Grade Geophone (adapted from Sensor Nederland b.v Literature)
Figure 2.10. Ideal Impulse Response Result
Figure 2.11. Electric Analogue of a Pile Segment (after Davis & Dunn, 1974)
Figure 2.12. Electric Analogue for a Defective Pile (after Davis & Dunn, 1974)
Figure 2.13. Ideal Resolution Chart
Figure 2.14. Ideal Sonic Echo Result: Velocity versus Time
Figure 2.15. Typical Testing Arrangement for Parallel Seismic Testing (adapted from Stain, 1982)
Figure 2.16. Idealized Parallel Seismic Profile
Figure 3.1. Plan of the National Geotechnical Experimentation Site (NGES) at Northwestern University
Figure 3.2. Soil Profile with CPT Data
Figure 3.3. Geotechnical Characteristics of NGES Soils
Figure 3.4. NDE Test Section, Plan View
Figure 3.5. Shear and Compression Wave Velocities of NGES Soils
Figure 3.6. Profile View of NGES Test Section
Figure 3.7. Detailed Schematic of Shaft 1 - Accessible Head Condition
Figure 3.8. Detailed Schematic of Shaft 2 - Accessible Head Condition
Figure 3.9. Detailed Schematic of Shaft 3 - Accessible Head Condition
Figure 3.10. Detailed Schematic of Shaft 4 - Accessible Head Condition
Figure 3.11. Detailed Schematic of Shaft 5 - Accessible Head Condition
Figure 3.12. Detailed Schematic of Shaft 1 - Inaccessible Head Condition
Figure 3.13. Detailed Schematic of Shaft 2 - Inaccessible Head Condition
Figure 3.14. Detailed Schematic of Shaft 3 - Inaccessible Head Condition
Figure 3.15. Detailed Schematic of Shaft 4 - Inaccessible Head Condition
Figure 3.16. Detailed Schematic of Shaft 5 - Inaccessible Head Condition
Figure 3.17. Unconfined Compression Test Results on Concrete Cylinders
Figure 3.18. Correlation between Propagation Velocity and Compressive Strength of Typical Concrete (after Davis and Robertson, 1975)
Figure 3.19. Change in Propagation Velocity with Concrete Age - Determined from UC and UPV Tests
Figure 4.1. Impulse Response Result - Shaft 3: Time Domain and Frequency Spectrum
Figure 4.2. Impulse Response Result - Shaft 3: Mobility Plot up to 2000 Hz
Figure 4.3. Impulse Response Result - Shaft 3: Mobility Plot up to 1000 Hz
Figure 4.4. Impulse Response Result - Shaft 4: Time Domain and Frequency Spectrum
Figure 4.5. Impulse Response Result - Shaft 4: Mobility Plot
Figure 4.6. Impulse Response Result - Shaft 5: Time Domain and Frequency Spectrum
Figure 4.7. Impulse Response Result - Shaft 5: Mobility Plot
Figure 4.8. Impulse Response Result - Shaft 1: Time Domain and Frequency Spectrum
Figure 4.9. Impulse Response Result - Shaft 1: Mobility Plot
Figure 4.10. Impulse Response Result - Shaft 2: Time Domain and Frequency Spectrum
Figure 4.11. Impulse Response Result - Shaft 2: Mobility Plot
Figure 4.12. Effect of Soil-Filled Joint on Mobility Plot: Comparison of Shafts 1 & 3
Figure 4.13. Effect of Neck Defect on Mobility Plot: Comparison of Shafts 2 & 4
Figure 4.14. Experimentally Determined Low-Strain Stiffness, K' as a Function of (a) Soil Conditions at Shaft Toe, and (b) Shaft Diameter
Figure 4.15. Impulse Response Result - Shaft 3 with Pile Cap: Time Domain and Frequency Spectrum
Figure 4.16. Impulse Response Result - Shaft 3 with Pile Cap: Mobility Plot
Figure 4.17. Impulse Response Result - Shaft 4 with Pile Cap: Time Domain and Frequency Spectrum
Figure 4.18. Impulse Response Result - Shaft 4 with Pile Cap: Mobility Plot
Figure 4.19. Impulse Response Result - Shaft 5 with Pile Cap: Time Domain and Frequency Spectrum
Figure 4.20. Impulse Response Result - Shaft 5 with Pile Cap: Mobility Plot
Figure 4.21. Impulse Response Result - Shaft 1 with Pile Cap: Time Domain and Frequency Spectrum
Figure 4.22. Impulse Response Result - Shaft 1 with Pile Cap: Mobility Plot
Figure 4.23. Impulse Response Result - Shaft 2 with Pile Cap: Time Domain and Frequency Spectrum
Figure 4.24. Impulse Response Result - Shaft 2 with Pile Cap: Mobility Plot
Figure 4.25. Center of Pile Cap Test - Pile Cap 1
Figure 4.26. Center of Pile Cap Test - Pile Cap 3
Figure 5.1. Propagation Velocity from Velocity-Time Plots versus Concrete Age
Figure 5.2. Propagation Velocity from Mobility Plots versus Concrete Age
Figure 5.3. Propagation Velocity from Embedded Geophone vs. Concrete Age
Figure 5.4. Propagation Velocity from All Field and Laboratory Tests as a Function of Concrete Age
Figure 5.5. Average Shaft Mobility versus Concrete Age
Figure 5.6. Low-Strain Stiffness versus Concrete Age
Figure 5.7. Resolution versus Concrete Age
Figure 5.8. Comparison of Rycon and Epoxy Couplants - Shaft 3
Figure 5.9. Comparison of Rycon and Epoxy Couplants - Shaft 5
Figure 5.10. Temperature Effects on Rycon Grease - Shaft 4
Figure 5.11. Comparison of Rycon and Duct Seal Couplants - Shaft 3
Figure 6.1. "Best Estimate" Numerically-Simulated and Experimental Mobilities: Shaft 3
Figure 6.2. "Best Estimate" Numerically-Simulated and Experimental Mobilities: Shaft 4
Figure 6.3. "Best Estimate" Numerically-Simulated and Experimental Mobilities: Shaft 5
Figure 6.4. "Best Estimate" Numerically-Simulated and Experimental Mobilities: Shaft 1
Figure 6.5. "Best Estimate" Numerically-Simulated and Experimental Mobilities: Shaft 2
Figure 6.6. "Best Fit" Numerically-Simulated and Experimental Mobilities: Shaft 3
Figure 6.7. "Best Fit" Numerically-Simulated and Experimental Mobilities: Shaft 4
Figure 6.8. "Best Fit" Numerically-Simulated and Experimental Mobilities: Shaft 5
Figure 6.9. "Best Fit" Numerically-Simulated and Experimental Mobilities: Shaft 1
Figure 6.10. "Best Fit" Numerically-Simulated and Experimental Mobilities: Shaft 2
Figure 6.11. Numerical Simulation of Shaft 1 with Varying Pile Cap Diameter
Figure 6.12. Numerical Simulation of Shaft 2 with Varying Pile Cap Diameter
Figure 6.13. Numerical Simulation of Shaft 3 with Varying Pile Cap Diameter
Figure 6.14. Numerical Simulation of Shaft 4 with Varying Pile Cap Diameter
Figure 6.15. Numerical Simulation of Shaft 5 with Varying Pile Cap Diameter
Figure 6.16. Factor to Determine "Effective" Area from Tributary Area of Pile Cap
Figure 6.17. Resolution of NGES Shafts Compared to Ideal Resolution Chart
Figure 6.18. Effect of Concrete Density Variation on Resolution
Figure 6.19. Effect of Soil Density Variation on Resolution
Figure 6.20. Effect of Embedment Layer Soil Stiffness of the Mobility Resolution
Figure 6.21. Resolution Chart for a Two-Layer Subsurface Profile, L/D = 10
Figure 6.22. Resolution Chart for a Two-Layer Subsurface Profile, L/D = 15
Figure 6.23. Resolution Chart for a Two-Layer Subsurface Profile, L/D = 20
Figure 6.24. Resolution Chart for a Two-Layer Subsurface Profile, L/D = 25
Figure 6.25. Resolution Chart for a Two-Layer Subsurface Profile, L/D = 30
Figure 6.26. Comparison of Cutoff Frequencies
Figure 7.1. Compiled Parallel Seismic Profile: Shaft 3 Access Hole 3
Figure 7.2. Compiled Parallel Seismic Profile: Shaft 1 Access Hole 1
Figure 7.3. Compiled Parallel Seismic Profile: Shaft 4 Access Hole 2
Figure 7.4. Compiled Parallel Seismic Profile: Shaft 5 Access Hole 2
Figure 7.5. First Arrival Times versus Depth: Shaft 1
Figure 7.6. First Arrival Times versus Depth: Shaft 2
Figure 7.7. First Arrival Times versus Depth: Shaft 3
Figure 7.8. First Arrival Times versus Depth: Shaft 4
Figure 7.9. First Arrival Times versus Depth: Shaft 5
Figure 7.10. First Arrival Time versus Distance from Shaft: Shaft 1
Figure 7.11. First Arrival Time versus Distance from Shaft: Shaft 2
Figure 7.12. First Arrival Time versus Distance from Shaft: Shaft 3
Figure 7.13. First Arrival Time versus Distance from Shaft: Shaft 4
Figure 7.14. First Arrival Time versus Distance from Shaft: Shaft 5
Figure 7.15. Comparison of Compression Wave Velocities from Results of Cross-Hole and Parallel Seismic Tests
Figure 7.16. Travel Path for Direct Wave
Figure 7.17. Travel Path for Refracted Wave
List of Tables
Table 2.1. Typical Propagation Velocities from Various Materials
Table 2.2. Range of Input Frequencies for Impulse Hammer Tips
Table 2.3. Analogous Relationships between Mechanical and Electrical Systems (after Richard, et al. (1970))
Table 3.1. Field Investigations at the Northwestern NGES
Table 3.2. NDE Test Section Details
Table 3.3. Summary of Casing and Liner Dimentions
Table 3.4. Length of Sonic Logging Access Tubes
Table 3.5. Spacing between Sonic Logging Access Tubes
Table 3.6. Cased Borehole Dimentions
Table 3.7. Dimensions of Pile Caps
Table 3.8. Average Density of Concrete Cylinders
Table 4.1. Summary of Impulse Response Results - Accessible-Head (Day 28)
Table 4.2. Summary of Accessible- and Inaccessible-Head Impulse Response Results
Table 6.1. Average Soil Parameters at NGES
Table 6.2. Summary of Shaft Parameter Changes for "Best Estimate" to "Best Fit" Simulations
Table 6.3. Summary of Soil Parameter Changes for "Best Estimate" to "Best Fit" Simulations
Table 6.4. Summary of "Best Estimate" Simulated and Experimental Mobility Results
Table 6.5. Summary of Resolution for Accessible-Head Impulse Response Tests
Table 6.6. Overconsolidation Ratio Exponent, K (after Hardin and Drnevich, 1972)
Table 6.7. Constant K2 as a Function of Void Ratio or Relative Density (after Seed and Idriss, 1970)
Table 6.8. Resolution Prediction from Two Layer Resolution Charts
Table 6.9. "Cutoff" Frequencies for Inaccessible Head Tests
Table 6.10. Cutoff Frequencies from Experimental and Empirical Methods
Table 6.11. Parameter Effects for Achieving "Best Fit Simulations
Table 7.1. Distance between Drilled Shafts and Access Holes (m)
Table 7.2. Summary of Results within 3 m of a Drilled Shaft
Table 7.3. Summary of Propagation Velocities in Concrete (m/s)
Table 7.4. Compression Wave Velocities from Parallel Seismic and Cross-Hole Seismic Tests
List of Symbols
Roman Letter Symbols
| A, Ac |
= |
cross-sectional area of concrete shaft |
| Ai |
= |
amplitude of normal incident stress wave |
| AR |
= |
amplitude of reflected stress wave |
| AT |
= |
amplitude of transmitted stress wave |
| B |
= |
depth of pile cap or grade beam |
| C |
= |
capacitance (electrical analogue) |
| d |
= |
travel distance |
| D |
= |
diameter |
| Dr |
= |
relative density |
| e |
= |
void ratio |
| E, Ec |
= |
Young's Modulus (elastic concrete modulus) |
| E' |
= |
apparent stiffness of pile head |
| f |
= |
frequency |
| fc |
= |
cutoff frequency |
| Df |
= |
change in frequency between resonant peaks |
| F |
= |
force |
| G |
= |
shear modulus |
| ic |
= |
critical angle of incidence |
| I |
= |
electrical current (electrical analogue) |
| K' |
= |
low-strain shaft head dynamic stiffness |
| L |
= |
length |
| LD |
= |
length to depth of anomaly |
| L, L', l |
= |
inductance (electrical analogue) |
| Mp |
= |
mass of shaft |
| m |
= |
point on mobility curve |
| N |
= |
mobility; mean value of V/F |
| P |
= |
maximum peak resolution |
| Q |
= |
minimum peak resolution |
| qu |
= |
unconfined compressive strength |
| qc |
= |
CPT tip resistance |
| r |
= |
radius |
| R |
= |
resistance (electrical analogue) |
| t |
= |
time |
| Dt |
= |
time increment |
| tc |
= |
contact time of impact |
| td |
= |
travel time for the direct wave |
| th |
= |
travel time for refracted wave |
| u |
= |
displacement |
| v |
= |
wave velocity |
| vvar |
= |
compression wave velocity in a rod |
| vc |
= |
compression wave velocity |
| vconc |
= |
propagation velocity in concrete |
| vo |
= |
partical velocity |
| vp |
= |
longitudinal wave velocity |
| vR |
= |
Rayleigh wave velocity |
| vs |
= |
shear wave velocity |
| V/F |
= |
modility (mechanical admittace) of shaft head |
| x |
= |
space |
| Dx |
= |
distance between shaft and access hole |
| Z |
= |
mechanical impedance |
Greek Letter Symbols
| α |
= |
angle of refraction |
| αp |
= |
refraced angle of compressive wave |
| αs |
= |
refraced angle of shear wave |
| αs |
= |
factor for pile cap plan area |
| αt |
= |
factor for relative thickness of pile cap |
 |
= |
damping factor |
 |
= |
Poisson's ratio |
| λ |
= |
wavelength |
| λc |
= |
wavelength where wave propagation in a rod is no longer one-dimensional |
| ρ |
= |
material density |
| ρc |
= |
concrete density |
| ρs |
= |
bulk density of soil surrounding shaft |
| σ |
= |
attenuation factor |
| σo' |
= |
mean normal effective stress |
| σv' |
= |
effective overburden stress |
 |
= |
angle of incidence |
| p |
= |
compression wave angle of incidence |
| s |
= |
shear wave angle of incidence |
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