Nondestructive Evaluation of Pavements A New Tool, The Rolling Dynamic Deflectometer RDD

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Nondestructive Evaluation of Pavements A New
Tool,The Rolling Dynamic Deflectometer (RDD)
byJames A. Bay, Utah State University jim.bay_at_usu
.eduKenneth H. Stokoe, II, The University of
Texas WASHTO Annual Meeting June 16-18,
2003 Salt Lake City, Utah
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Outline

• Description of the RDD
• Typical RDD Deflection Profiles
• Conclusions
• Engineering Geophysical Measurements for
  Earthquake Design

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Description of the RDD

• Applies large cyclic loads to the pavement as it
  travels
• Measures induced deflections
• Highly modified Vibroseis truck used for oil
  exploration

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The RDD
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Basic Systems of the RDD
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RDD Loading Systems
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Rolling Deflection Sensor
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Plan View of RDD Deflection Sensors
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RDD Specifications

• Dynamic Force 0-70 kips(0-310 kN) p-p
• Static Force 0-50 kips (0-224 kN)
• Testing Velocity 0-2 ft/sec (0-0.6 m/s)
• Operating Frequency 5 -100 Hz

Soon to increase to about 4 ft/sec with new
generation of rolling deflection sensor
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Forcing Function Applied to Pavement by RDD
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• All moving deflection measurements are inherently
  noisy because of pavement roughness
• The RDD eliminates the effects of noise by
  tuning in the operating frequency exactly like
  you tune your radio to a specific station

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Typical RDD Deflection Profiles
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Rigid Airport PavementDFW Runway 17R-35L
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DFW Runway Construction

• Dowelled Transverse Joints Every 15.2 m (50 ft)
• Sawn Joints Midway Between Dowelled Joints

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Expanded Deflection Profile
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Note limited region Not effected by joint
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Flexible Highway Pavement,IH-35, Near Hillsboro,
TX
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Asphalt Overlaid Rigid Airport Pavement, Main
North-South Taxiway, Majors Field, Greenville,
Texas

• Rigid Pavement Constructed in the 1940s
• Overlaid with Asphalt around 1990
• Recently Constructed Pavements at Cross-Taxiways

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Expanded Deflection Profile
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RDD Deflection Basins
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Conclusions

• The RDD is a powerful tool for assessing the
  condition of flexible and rigid pavements
• Continuous deflection profiles give a much more
  complete picture of pavement behavior than
  discrete measurements
• Continuous deflection profiles show the
  performance critical features such as joints and
  cracks
• There is little danger of missing critical
  pavement regions with a continuous profile
• Continuous profiles show regions where 1-D
  back-calculation should and should not be used

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IBC 2000 Requires VS30 (average shear wave
velocity in top 30 m of soil profile) For Seismic
Design

• Determine design response spectra (base shear)
• Shear wave velocity profile can also be used in
  assessment of liquefaction susceptibility
• Spectral-Analysis-of-Surface-Waves (SASW) is a
  powerful method for measuring shear wave velocity
  profiles

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SASW
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SASW

• Requires no boreholes
• Quick and inexpensive
• Measures shear wave velocity profile
• Detects soft layer beneath stiff layers
• Measures average properties of large volume of
  soil
• Cannot resolve thin, deep layers

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USU SASW Drop Weight Source
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USU SASW Source

• 4500-lb drop weight
• Optimized to measure shear wave velocity profile
  at any site
• Works well in urban environments using very low
  (1-2 in.) drop heights

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Example of SASW Measurement
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Experimental Dispersion Curve
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Experimental and Theoretical Curves
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Shear Wave Velocity Profile
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NEHRP Shallow Profiling Project

• Use SASW to measure Vs30 (and deeper) at 45 sites
  in poorly characterized site response units in
  Salt Lake Valley
• Utah State University (James Bay)
• Utah Geological Survey (Francis Ashland)
• Utah Seismograph Station (Kris Pankow)

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Thank you