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 (419) 530-8133 Voice (419) 530-8116 Fax [email protected] Purpose of Presentation.

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Evaluation of seasonal effects on subgrade soils

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

(419) 530-8133 Voice

(419) 530-8116 Fax

[email protected]


Purpose of presentation
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




General expression
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 (=2π/365.25)

    f = time shift in days


Measured and computed mean daily air temperatures
Measured and Computed Mean Daily Air Temperatures

T(t) = 10.70 + 12.39 sin[2π/365.25 (t - 109)]





Volumetric water content and depth to water table pcc section
Volumetric Water ContentAnd Depth to Water Table (PCC Section)


Volumetric water content and depth to water table ac section
Volumetric Water ContentAnd Depth to Water Table (AC Section)



Volumetric water content and average soil temperature ac section
Volumetric Water Content and Average Soil Temperature(AC Section)

VMC(t) = 37.1 + 1.66 sin[2π/365.25 (t - 130)]


Calculation of seasonal variation of subgrade soil resilient modulus
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


Calculation of weight factors for resilient modulus
Calculation of Weight Factors for Resilient Modulus Modulus

  • Equation for weighting factors

  • Weighting factors are computed using the mean resilient modulus



Conclusions
Conclusions (AC Section)

  • 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


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