LAUSR

Determination of the modulus of subgrade reaction (ks) is an essential geotechnical design parameter that describes the relationship between stress and the associated settlement of soils. The ks is typically obtained using a laborious and costly method called the plate load test (PLT), and thus, to overcome the limitations related to the PLT, determining an alternative testing technique that can easily predict the ks is a priority. The feasibility of using a light weight deflectometer (LWD), also known as the dynamic PLT, to determine the ks of unbound pavement layers was thus investigated in this research. Eighteen laboratory testing models of granular soils were prepared and tested using the dynamic PLT (LWD) in conjunction with the static PLT (PLT). The soils’ characteristics examined under both dynamic and static loading conditions were analyzed and correlated. A series of multiple nonlinear regression analyses were conducted using three groups of independent variables: (1) LWD measurements, (2) basic soil properties, and (3) LWD data plus basic soil properties. Several nonlinear regression models were developed to predict the modulus of subgrade reaction on the basis of the LWD measurements and selected soil characteristics. The results revealed that certain LWD measurements, including dynamic modulus (Ed), surface deflection (δ), and degree of compatibility (Dc), are strongly correlated with the results from PLT. Additionally, good correlations were identified between ks and maximum dry density, suggesting that using LWD measurements along with basic soil properties yields correlations with adequate prediction quality.