AASHTO T 307-99 (2021) PDF Download

The AASHTO T 307-99 (2021) standard provides procedures for preparing and testing untreated subgrade soils and untreated base/subbase materials to determine their resilient modulus (Mr). Resilient modulus is a measure of the elastic modulus of these materials under conditions that simulate the physical conditions and stress states of materials beneath flexible pavements subjected to moving wheel loads.

This standard is applicable to undisturbed samples of natural and compacted subgrade soils, as well as disturbed samples of subgrade soils and untreated base/subbase prepared for testing in the laboratory. The stress levels used for testing specimens for resilient modulus are based on their location within the pavement structure. Samples located in the base and subbase are subjected to different stress levels compared to those from the subgrade.

The determination of resilient modulus values using this standard can be used in structural response analysis models to calculate the pavement structural response to wheel loads. It can also be used in pavement design procedures to design pavement structures. The resilient modulus values take into account certain nonlinear characteristics of the materials being tested.