Correlation of resilient modulus of fine-grained soils with common soil parameters for use in design of flexible pavements

Abstract

This thesis describes research conducted at the University of Hawaiʻi at Manoa to evaluate the resilient modulus properties of tropical Hawaiian fine-grained soils for use in flexible pavement design. The objectives of this study were to: a) measure the resilient modulus of four fine-grained soils found on the island of O'ahu, and b) develop predictive equations for resilient modulus based on easily measured soil index properties. Each soil was tested at 100% and 95% relative compaction based on the Standard Proctor compaction test. At each relative compaction, the soils were compacted at three different water contents: at optimum, 2% above and 2% below optimum. Correlations were developed based on two resilient modulus stress-state models published by Uzan (1985) and Ni et al. (2002). Regression parameters obtained from the Uzan and Ni et al. models are correlated to soil index properties and physical-state conditions. A total of four regression models are proposed which correlate the resilient modulus to soil stress-state, physical-state, and soil index properties. Tropical soils may undergo irreversible changes upon drying, resulting in permanent alterations in soil properties. As a result, the resilient modulus of an MH soil was measured at three different stages of drying as follows: (1) at the in situ state; (2) after drying the soil to half the natural water content; and (3) after oven drying. In general, the resilient modulus was found to be more sensitive to changes in confining and deviatoric stresses upon increasing the degree of drying.