Pavement performance analysis considering the influence of suction and temperature on subgrade soil modulus

Subgrade soils can experience varying suction (equivalent to moisture) and temperature, which could affect the modulus of subgrade soil and the response of flexible pavements. The influence of these two factors on pavement performance has not been explored on purpose despite their importance in a changing climate. In this study, a simple approach was proposed for analyzing pavement performance with consideration of suction and temperature effects on soil modulus. Modulus values at different conditions of suction and temperature are calculated using a semi-empirical equation. Then, they are utilized in the numerical software KENLAYER to evaluate the stress and strain distributions in pavements composed of an asphalt layer, base layer, and subgrade layer based on linear elastic theory. The computed results are used to predict the rutting and fatigue cracking using some field-calibrated semi-empirical equations. In parametric studies using this method, the suction and temperature-dependent modulus of a clayey soil determined from laboratory experiments was applied. The results reveal that an increase in subgrade soil modulus due to drying and cooling can reduce the total rut depth mainly due to a reduction of the vertical compressive strain in the subgrade layer. For instance, a change in suction from 0 to 150 kPa (equivalent to optimum moisture content of the clayey soil) can lead to a 34% decrease in the total rut depth. However, the effects of an increase in soil subgrade modulus on fatigue cracking are influenced by the asphalt thickness. A reduced subgrade modulus because of wetting and heating decreases horizontal tensile strain (less susceptible to fatigue cracking) at the lowest section of relatively thinner asphalt but increases horizontal tensile strain for thicker asphalt.