Resilient behavior of stabilized subgrade soils

The purpose of this thesis was to study the behavior of stabilized subgrade soils under the short duration repeated loads simulating those applied by traffic to pavement structures. The resilient modulus and unconfined compressive strength were used to describe this behavior.;For the study, five typical North Carolina soils having AASHTO classifications A-4 to A-7 were mixed with 3%, 4%, and 5% lime and 8%, 10%, and 12% cement at different water contents and tested. Specimens measuring 2" of diameter and 4" of height were prepared by kneading compaction for the tests. The lime-stabilized specimens were mellowed for one hour before compacting and cured for 48 hours at 77;The results of the study indicate that lime and cement stabilization significantly increased both the resilient modulus and unconfined compressive strength of the soils tested. These properties varied randomly within the tested water content range from optimum moisture content (OMC), to OMC + 4%. Different patterns of resilient modulus vs. applied deviator stress were observed in different tests. Six different graph types were defined to describe the behavior. Both lime and cement stabilization had optimum additive levels that gave a maximum resilient modulus and a maximum unconfined compressive strength.;The test results were used to calculate the structural layer coefficients of stabilized subgrades. The analyses showed that layer coefficients increase with increasing subgrade resilient modulus and decrease with increasing base course resilient modulus.;A separate study using two other soils blended with aggregate indicated aggregate stabilization is more effective for soils having less than 50% fines when they are compacted dry of optimum.