Evaluation of resilient modulus model parameters for mechanistic-empirical pavement design

Correlations were developed to estimate the resilient modulus of various Wisconsin subgrade soils from basic soil properties. A laboratory testing program was conducted on common subgrade soils to evaluate their physical and compaction properties. The resilient modulus of the investigated soils was determined from repeated load triaxial testing according to the AASHTO T 307 procedure. The laboratory testing program produced consistent results and a high-quality database. The resilient modulus constitutive equation adopted by NCHRP Project 1-37A was selected for this study. Comprehensive statistical analysis was performed to develop correlations between basic soil properties and the resilient modulus model parameters k(i). The analysis did not yield good results when the whole test database was used. However, good results were obtained when fine-grained and coarse-grained soils were analyzed separately. The correlations developed were able to estimate the resilient modulus of the compacted subgrade soils with reasonable accuracy. To inspect the performance of the models developed in this study, comparison with the models developed on the basis of the Long-Term Pavement Performance (LTPP) database was made. The LTPP models did not yield good results compared with the models proposed by this study because of differences in the test procedures, test equipment, sample preparation, and other conditions involved with development of both LTPP and the models of this study.