AASHTO T 307:99(2017) Standard Method of Test for Determining the Resilient Modulus of Soils and Aggregate Materials.
This method covers procedures for preparing and testing untreated subgrade soils and untreated base/subbase materials for determination of’ resilient modulus (M,) under conditions representing a simulation of the physical conditions and stress states of materials beneath flexible pavements subjected to moving wheel loads.
The methods described are applicable to undisturbed samples of natural and compacted suhgrade soils, and to disturbed samples of subgrade soils and untreated base/subbase prepared for testing by compaction in the laboratory.
In this method, stress levels used for testing specimens for resilient modulus are based on the location of the specimen within the pavement structure. Samples located within the base and subbase are subjected to different stress levels as compared to those specimens that are from the subgrade. Generally, specimen size for testing depends on the type of material based on the gradation and the plastic limit of the material as described in a later section.
The value of resilient modulus determined from this procedure is a measure of the elastic modulus of untreated base and subbase materials and subgrade soils recognizing certain nonlinear characteristics.
Resilient modulus values can be used with structural response analysis models to calculate the pavement structural response to wheel loads, and with pavement design procedures to design pavement structures.
Note 1 -Test specimens and equipment described in this method may be used to obtain other useful and related information such as the Poisson’s ratio and rutting characteristics of subgrade soils and base/subbase materials. Procedures for obtaining these are not covered in this standard.
untreated granular base and subbase materials—these include soil-aggregate mixtures and naturally occurring materials. No binding or stabilizing agent is used to prepare untreated granular base or subbase layers. These materials may be classitied as either Type 1 or Type 2 as subsequently defined in Sections 3.3 and 3.4.
3.2. suhgrade—subgrade soils are prepared and compacted before the placement of subbase and/or base layers. These materials may be classified as either Type 1 or Type 2 as subsequently defined in Sections 3.3 and 3.4.
3.3. Material Tipe 1—for the purposes of resilient modulus testing, Material Type I includes all untreated granular base and subbase material and all untreated subgrade soils that meet the criteria of less than 70 percent passing the 2.00-mm (No. 10) sieve and less than 20 percent passing the 75-um (No. 200) sieve, and that have a plasticity index of 10 or less. Soils classified as Type I will be molded in a 1 50-mm diameter mold.AASHTO T 307 pdf download.