Resilient modulus of subgrade materials for mechanistic-empirical pavement design guide

This paper describes the test program, proposed test protocol for subgrade resilient modulus (Mr), determination of Mr values, and development of design tables and constitutive models for Mr estimations. Subgrade samples were collected from 12 locations throughout the state of Wyoming, USA for standard laboratory and Mr tests. The proposed Mr test protocol was validated using test data collected from a Round Robin Test Program. The study shows that Mr values of soils having R > 50 increase with increasing deviator stresses. In contrast, Mr values of soils having R ≤ 50 decrease with increasing deviator stresses. Design tables of Mr values were developed. Also, three constitutive models were locally calibrated for Mr estimations. The constitutive Model Type B yields a relatively better estimation of the resilient modulus than Models A and C. The proposed methods could be adopted to increase the efficiency of pavement design in the USA and other countries.