Subgrade Design Parameters from Samples Prepared with Different Compaction Methods

The standard and modified Proctor compaction tests have been widely used for evaluation of design properties and compaction characteristics of subgrade soils. However, different types of compaction roller equipment, each producing a different level of soil compaction, are used in the field for compaction of subgrade soils. The purpose of this paper is to evaluate the design properties of compacted subgrade soils using the gyratory compactor made by Servopac to simulate field compaction conditions. Field compaction data were collected from a road construction site in Pusan, Korea. After compaction of the subgrade soil in the field using a vibratory roller was concluded, block samples of the subgrade material were collected. Disturbed soil samples were collected for preparation of specimens in the laboratory using the Proctor compaction and gyratory compaction methods. Unconfined compression test results show that the peak strength, cohesion, and elastic modulus values of the specimens prepared from the field block samples and that of the specimens prepared using the Superpave gyratory compactor with a $600\mathrm{kPa}$ vertical pressure are similar. On the other hand, much higher values were obtained for these quantities for the laboratory specimens prepared using the modified Proctor method. Our test results indicate that the evaluation of design properties of subgrade soils based solely on the Proctor compaction tests may not be appropriate.