Resilient Behaviors of Compacted and Unsaturated Subgrade Materials

Abstract

Resilient modulus (M R ) of pavement materials has been used as the important parameter in the design of pavement structure in accordance with the new Mechanistic Empirical Pavement Design Guide (MEPDG) and 1993 AASHTO flexible pavement design guide. This paper studies the M R properties of compacted, unsaturated subgrade materials collected from Minnesota and Louisiana, and the effect of compaction moisture content on the M R properties of these soils is also investigated. Initially, the soil samples were tested to determine the soil-water characteristic curves (SWCCs) with Tempe cell method and filter paper technique. Then, M R tests were performed in accordance with the AASHTO T-307-99 standard at five different moisture content-dry density conditions, and the soil suctions at the compaction stages were estimated based on the SWCCs' information. The testing results indicated that compaction moisture content affects the values of resilient modulus of the subgrade soils. The specimens compacted at dry side of optimum moisture content (OMC) showed higher values of resilient modulus compared with those compacted at OMC and wet side of OMC. In addition, the use of the modified universal model and the model proposed by Cary and Zapata to predict M R value were also studied and analyzed in detail.