Comparison and Correction of Modulus Reduction Models for Clays and Silts

Prediction models of normalized modulus reduction curves ($G/G_{\text{max}}$) for clays and silts have been proposed by several researchers in the past decades. However, model uncertainties have been recognized in these studies. This study compares five prediction models of $G/G_{\text{max}}$ from previous studies, which use common predictor variables of cyclic shear strain amplitude, effective confining stress, and plasticity index. The relative differences between these models are described against these predictor variables. Then the model biases are evaluated through residual analyses using the modulus reduction database. Modulus reductions of $G$ are also discussed by combining the prediction models of $G/G_{\text{max}}$ and $G_{\text{max}}$ to illustrate the importance of these combinations. Correlations among the residuals of ln($G$) are calculated, and the correction factors of the $G/G_{\text{max}}$ model are presented conditioned on the $G_{\text{max}}$ and shear strength measurements.