The main goal of this study was to develop a set of testing procedure for resilient modulus and to provide a set of resilient modulus data on typical Indiana soils. Soils tested were five cohesive soils and one granular soil. Resilient modulus tests were performed in the laboratory on a fully automated repeated-load triaxial equipment according to AASHTO T 274-82.

A set of correlations was developed between the resilient modulus and the unconfined compression test results for normal and thawed subgrade conditions, based on the test results on the specimen sampled from existing subgrades. Freeze-thaw and post compaction water content increase effects were simulated in the laboratory by using a freeze-thaw chamber and an injection technique respectively. The resilient modulus for frozen subgrade was also determined.

A nonparametric statistical technique was applied to identify a laboratory compaction method capable of replicating the field compacted fabric. Fabric studies on the soils investigated were performed using a mercury intrusion porosimeter. Deformability and resilient response were explained by the fabric of compacted and uncompacted (powdered) soils.

A simplified design procedure was developed and it can be incorporated into 1986 AASHTO Guide for Design of Pavement Structures. Developed correlation for normal subgrade condition will help field engineers control the resilient properties of subgrade during construction. Also provided is the procedure to determine the resilient modulus at specific levels of stresses using the design charts developed.

Report Number



resilient modulus, pavement design, subgrade, soil fabric, HPR-2032

SPR Number


Publisher Place

West Lafayette, IN

Date of this Version