Resilient modulus of cohesive soils and the effect of freeze–thaw

Resilient modulus tests were performed on five cohesive soils sampled from the subgrades of in-service pavements. The stress at 1% strain in the unconfined compression test (Su1.0%) was found to be a good indicator of the resilient modulus (MR), and an empirical relationship between MRand Su1.0%was obtained. The proposed relationship itself is not affected by the changes in subgrade after construction and, therefore, is applicable to as-compacted and in-service subgrade conditions. Closed-system freeze–thaw tests were also performed and the effect of freeze–thaw on the resilient modulus was studied. There is a negligible effect of freeze–thaw, without ice lens formation, for soils having values of Su1.0%less than 8 psi (55 kPa), while the effect of freeze–thaw increases as the value of Su1.0%increases. For example, a soil with a value of Su1.0%greater than 15 psi (103 kPa) would exhibit more than 50% reduction in resilient modulus due to the effect of freeze–thaw. The resilient modulus of frozen cohesive soil is independent of the repeated deviator stress.