Evaluation Of Seasonal Effects On Subgrade Soils

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Evaluation Of Seasonal Effects On Subgrade Soils

•  TRB PAPER 03-03801
•  Andrew G. Heydinger
• Mail Stop 307
• Department of Civil Engineering
• University of Toledo
• Toledo, OH 43606-3390
• [phone] Voice
• [phone] Fax
• aheyding_at_eng.utoledo.edu

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Purpose of Presentation

• Present general expressions for the seasonal
  variations of air temperature and subgrade soil
  temperature and moisture
• Discuss effects of precipitation and depth to
  ground water table on the subgrade soil
• Use seasonal variations of subgrade soil moisture
  to determine the mean monthly variations of
  resilient modulus and weighting factors

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ODOT SHRP Test Road
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Test Sections
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General Expression

• Based on Fourier transform of the time series
• F(t) A0 B1 sin?(t-f)
•  
• t time expressed as the day of the
  year
•  
• A0 mean value
•  
• B1 the amplitude
•  
• ? the normalized frequency
  (2p/365.25)
•  
• f time shift in days

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Measured and Computed Mean Daily Air Temperatures

• T(t) 10.70 12.39 sin2p/365.25 (t - 109)

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Mean Daily Temperatures (PCC Section)
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Mean Daily Temperatures (AC Section)
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Volumetric Water Content and Precipitation (AC
Section)
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Volumetric Water ContentAnd Depth to Water Table
(PCC Section)
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Volumetric Water ContentAnd Depth to Water Table
(AC Section)
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Volumetric Water Content and Average Soil
Temperature (PCC Section)
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Volumetric Water Content and Average Soil
Temperature(AC Section)

• VMC(t) 37.1 1.66 sin2p/365.25 (t - 130)

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Calculation of Seasonal Variation Of Subgrade
Soil Resilient Modulus

• Equation for Mr from lab tests on subgrade soil
• Mr(psi) 77235.54 - 639.121S() - 5418.33sd
• Used mean values of VMC for each month and n
  40 to compute mean monthly S()
• Used mean monthly S() and sd 1.2 psi to
  compute mean monthly Mr

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Calculation of Weight Factors for Resilient
Modulus

• Equation for weighting factors
• Weighting factors are computed using the mean
  resilient modulus

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Example Calculation for Resilient Modulus
Weighting Factors (AC Section)
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Conclusions

• Data from Ohio SHRP Test Pavement was analyzed
  for seasonal variations
• Subgrade soil VMC was not correlated to
  precipitation or depth to the GWT
• Fourier transform analyses were used to express
  seasonal variations using mean daily values
• Subgrade soil VMC was used to predict mean
  monthly variations of resilient modulus and
  weighting factors