Estimating the Resilient Modulus of Marginal Granular Materials through a Novel Approach of Strain-Stage Dynamic CBR Test

Abstract

Stiffness quantification of unbound granular materials (UGMs) is essential for designing pavement structures. This stiffness can be determined directly through the resilient modulus test, or indirectly, by correlation, with the California bearing ratio (CBR) test. Alternatively, the dynamic CBR test (dCBR) has been proposed as a simple and low-cost method for this assessment. This study investigated a new dCBR test protocol based on a novel strain-stage approach, applying 20 load cycles/stage. This testing protocol is expected to facilitate characterization and on-site control of stiffness for UGMs, including marginal granular materials (MGMs). The study characterized four MGMs using the new dCBR test protocol and the resilient modulus test; four replicate specimens manufactured by gyratory compaction were assessed per material and test. The protocol was implemented successfully for the MGMs studied to compute an equivalent resilient modulus. A methodology is proposed for calculating an adjusted equivalent resilient modulus with values similar to those of the resilient modulus. Further research is suggested to explore the relationship between the dCBR and CBR tests to advance the characterization of granular materials for pavement structures and expand the experimental data using a broader set of soils to validate the protocol.