Effect of Soil Parameters on Elastic Characteristics of Subgrade Materials

In this paper, state-dependent elastic characteristics of granular subgrade materials were investigated, assuming various field conditions. For this purpose, a series of resonant column tests were conducted. The test materials were cohesionless soils consisting of clean and silty sands with different fines contents. The effects of moisture content, overconsolidation ratio, relative density, and confining stress on the elastic modulus were analyzed. From the test results, it was observed that the initial shear modulus, G0, decreases with increasing moisture content because of reduced particle contact friction. Higher fines content produced a more pronounced modulus reduction at the same moisture content. It was also found that the effect of fines content on G0 becomes smaller as the relative density and confining stress increase. These results indicate that the moisture effect on G0 is important at shallow depths such as subgrade layers. A modulus reduction factor was proposed, which can reflect the effect of the soil parameters on elastic modulus. A resilient modulus (MR) model modified on the basis of the test results was proposed and finite-element analyses were conducted. Two case examples were selected from the literature to verify the proposed MR model. Predicted MR values obtained using the proposed model showed reasonable agreement with measured values from the selected case examples.