Integrated approaches for predicting soil-water characteristic curve and resilient modulus of compacted fine-grained subgrade soils

This paper combines a series of approaches for predicting the soil-water characteristic curve (SWCC) and the variation of the resilient modulus (M-R) of compacted fine-grained subgrade soils with moisture content, which is the key information required in mechanistic pavement design methods. The presented approaches for the SWCC and M-R are integrated, as (i) they are developed following the same philosophy, (ii) they require only the measurements of the suction and moisture content or M-R at saturated and optimum moisture content conditions for prediction, and (iii) the predicted SWCC is used for predicting the M-R - moisture content relationship. Experimental studies have been performed on five fine-grained subgrade soils that were collected from different regions in Ontario, Canada, to determine their M-R at various external stress levels and post-compaction moisture contents, as well as their SWCCs after the M-R tests. Experimental measurements are predicted using the integrated approaches and the empirical approaches currently used in the mechanistic-empirical pavement design guide (MEPDG). It is demonstrated that the integrated approaches are easy to use and show improved reliability in predicting both the SWCC and M-R for the investigated subgrade soils in spite of using limited experimental data.