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# Evaluation Of Seasonal Effects On Subgrade Soils - PowerPoint PPT Presentation

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

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

• 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

• 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

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

Volumetric Water ContentAnd Depth to Water Table (PCC Section)

Volumetric Water ContentAnd Depth to Water Table (AC Section)

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

• 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

• Equation for weighting factors

• Weighting factors are computed using the mean resilient modulus

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