Resilient modulus of subgrade is often necessary for pavement design anddetermined by cyclic triaxial tests or correlation with other laboratory or insitu testresults (such as CBR and DCP data). Cyclic plate loading tests were conducted inthis study to determine the resilient modulus of a weak subgrade. The weaksubgrade was made of 75% Kansas River sand and 25% kaolin and compacted atwet of optimum in a large geotechnical testing box (2m x 2.2m x 2m). Thissubgrade was first evaluated by DCP tests and then tested under a 30-cm diameterrigid plate at four different magnitudes of cyclic loading. During the tests, thedeformations of the plate and the subgrade surface were monitored. The testresults showed that the plate deformation increased with the number of cycles. Anelastic solution was used based on the rebound deformation of the plate to calculatethe resilient modulus of the subgrade. The calculated resilient modulus of thesubgrade decreased and approached a stable value with the number of cycles underdifferent magnitudes of cyclic loading. The calculated resilient modulus from thecyclic plate loading tests was compared with that determined based on thecorrelation with the CBR value of the subgrade.
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