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 (S-u1.0%) was found to be a good indi cator of the resilient modulus (M(R)), and an empirical relationship b etween M(R) and S-u1.0% was obtained. The proposed relationship itself is not affected by the changes in subgrade after construction and, th erefore, is applicable to as-compacted and in-service subgrade conditi ons. Closed-system freeze-thaw tests were also performed and the effec t of freeze-thaw on the resilient modulus was studied. There is a negl igible effect of freeze-thaw, without ice lens formation, for soils ha ving values of S-u1.0% less than 8 psi (55 kPa), while the effect of f reeze-thaw increases as the value of S-u1.0% increases. For example, a soil with a value of S-u1.0% greater than 15 psi (103 kPa) would exhi bit more than 50% reduction in resilient modulus due to the effect of freeze-thaw. The resilient modulus of frozen cohesive soil is independ ent of the repeated deviator stress.