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

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 (MR) and soil suction. AASHTO 2002 Design guide MR predictive model was used and evaluated for its reliability in predicting MR values. Findings from MR and soil suction tests showed that MR increased as total and matric suctions increased. The variation of MR with both suctions revealed the same trends. Additionally, an existing MR-stress-suction model was modified to evaluate the variation of MR with suction and stresses. The modified model was a reliable predictor of MR values of unsaturated subgrade soils.