An Alternative Test for the Resilient Modulus of Fine Grained Subgrades: Fid-Bau Portal

An Alternative Test for the Resilient Modulus of Fine Grained Subgrades

Smolen, Jonathan M. / Drumm, Eric C. / Thomas, Kenneth G.

For mechanistic design of pavement systems based on elastic theory, the resilient modulus is used to characterize the soil subgrade. The standard procedure for obtaining resilient modulus is a repeated load triaxial test under a range of stress states. This test is complicated and expensive, and as a result many commercial laboratories will not conduct these tests but instead rely on empirical relationships. An alternative test method was developed in which a hammer of known mass falls onto a volume of soil, and the acceleration response of the falling weight used to calculate the modulus. While this approach has been used by others, the device described here is new and tests fine-grained soil in an unconfined state. The alternative test method was used on 4 different soils and the results compared with results obtained from the standard repeated load test. The alternative test produced reasonably consistent results and appears to measure a material response that correlates well with the standard triaxial resilient modulus test results. The device was also used to demonstrate the decrease in modulus with increasing water content. It is suggested that the alternative test for resilient modulus may be a cost-effective approximation for mechanistic pavement design for projects where the complete standard test is not warranted.