1. 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 aheyding@eng.utoledo.edu

2. 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

3. ODOT SHRP Test Road

4. Test Sections Test Sections

5. General Expression Based on Fourier transform of the time series: F(t) = A 0 + B 1 sin[  (t-  )] t = time expressed as the day of the year A 0 = mean value B 1 = the amplitude  the normalized frequency (=2π/365.25)  = time shift in days

6. Measured and Computed Mean Daily Air Temperatures T(t) = 10.70 + 12.39 sin[2π/365.25 (t -  )]

7. Mean Daily Temperatures (PCC Section)

8. Mean Daily Temperatures (AC Section)

9. Volumetric Water Content and Precipitation (AC Section)

10. Volumetric Water Content And Depth to Water Table (PCC Section)

11. Volumetric Water Content And Depth to Water Table (AC Section)

12. Volumetric Water Content and Average Soil Temperature (PCC Section)

13. Volumetric Water Content and Average Soil Temperature (AC Section) VMC(t) = 37.1 + 1.66 sin[2π/365.25 (t -  )]

14. Calculation of Seasonal Variation Of Subgrade Soil Resilient Modulus Equation for M r from lab tests on subgrade soil M r (psi) = 77235.54 - 639.121S(%) - 5418.33  d Used mean values of VMC for each month and n = 40% to compute mean monthly S(%) Used mean monthly S(%) and  d = 1.2 psi to compute mean monthly M r

15. Calculation of Weight Factors for Resilient Modulus Equation for weighting factors Weighting factors are computed using the mean resilient modulus

16. Example Calculation for Resilient Modulus Weighting Factors (AC Section)

17. 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