Determination of Resilient Properties of Unbound Materials with Diametral and Cyclic Triaxial Test Systems

Repeated load diametral test systems are experiencing increased use to determine resilient properties of asphalt concrete and admixture stabilized materials. For these materials, the resilient properties obtained with the diametral test systems compare favorably to properties determined with conventional repeated load triaxial test systems. To date, repeated load diametral test systems have not been used extensively to determine the resilient properties of unbound materials. This is due, in part, to the fact that comparative studies between the properties obtained with the diametral test systems and the repeated load triaxial test systems have not been made. In response to the need to establish a correlative data base between resilient properties determined with repeated load diametral and triaxial test systems, a laboratory test program was conducted. Specifically, resilient properties of two base-course and two cohesionless-subgrade soils were determined using both repeated load triaxial and diametral test systems. The resilient properties of duplicate specimens (with respect to water content, dry density, and method of compaction) were compared over a range of stress conditions. The resilient properties determined with either the repeated load diametral or triaxial test systems were approximately equivalent. The maximum differences between resilient moduli for comparable states of stress were ±80%. Correlations between resilient moduli can be only made for a specific material at a given water content, dry density, and method of compaction. It was not possible with the data set developed in the study to establish general correlation factors between resilient properties determined with diametral or triaxial test systems.