Evaluation of Resilient Modulus Test Protocols for New Mexico Subgrade Soil

Abstract

Resilient modulus (MR) is a laboratory determined parameter of pavement subgrade soil which is an important design input for the Mechanistic Empirical Pavement Design Guide (MEPDG). There are two accepted laboratory testing protocols for determining MR, namely AASHTO T307 and NCHRP 1-28A. AASHTO method is more popular because of its simplicity in positioning the load and deformation transducers. This study is undertaken to examine the available test protocols for New Mexico subgrade soil by varying the location of deformation transducers and effects of sample size. AASHTO A-6 subgrade soils have been collected from the state of New Mexico, USA. Specimens of 2.8 inch and 4 inch diameters are reconstituted using modified proctor compaction.Resilient modulus values aredetermined using external and internal deformation techniques. Comparative analyses are performed and amount of extraneous large deformation (lower MR) measured by the AASHTO recommended external deformation transducers is measured.In addition, appropriate internal deformation measurement methods are recommended to obtain most consistent MR values. 2.8 inch and 4 inch diameter sample generate almost similar MR values.