Environmental influences on the engineering behavior of unsaturated undisturbed subgrade soils: effect of soil suctions on resilient modulus

Abstract This study evaluated the effect of soil suction on resilient modulus of undisturbed subgrade soil specimens collected from a section located on I-40 in Canadian County, Oklahoma. A total of 18 undisturbed specimens were tested for resilient modulus (<i>M_R</i>) and soil suction. AASHTO 2002 Design guide <i>M_R</i> predictive model was used and evaluated for its reliability in predicting <i>M_R</i> values. Findings from <i>M_R</i> and soil suction tests showed that <i>M_R</i> increased as total and matric suctions increased. The variation of <i>M_R</i> with both suctions revealed the same trends. Additionally, an existing <i>M_R</i>-stress-suction model was modified to evaluate the variation of <i>M_R</i> with suction and stresses. The modified model was a reliable predictor of <i>M_R</i> values of unsaturated subgrade soils.