Regression models for dynamic properties of highly organic soils

Regression models are presented for the dynamic properties of highly organic soils. The models are based on a database of triaxial and resonant-column/torsional-shear cyclic loading tests on thin walled tube samples mainly retrieved from the Sacramento-San Joaquin Delta. The soils in this database range from highly fibrous peat to amorphous organic clays with organic contents (OC) ranging from 14-81%, water contents ranging from 88-495%, total densities (p) ranging from 1.056-1.450 Mg/[m.sup.3], and effective consolidation stresses ([[sigma]'.sub.vc] ranging from 11-135 kPa. The secant shear modulus (G) and equivalent damping ratio ([xi]) were modeled as variables dependent on the shear strain amplitude ([[gamma].sub.c]), consolidation stress ([[sigma].sub.vc]), and OC. The residuals of the regression models were analyzed against other predictor variables including undisturbed density ([rho]), loading frequency (f), and number of loading cycles (N). A regression model for [rho] was developed, and conditional probabilities were used to improve the estimation of G and [xi] when p measurements were available. The database of in situ measurements of shear wave velocity ([V.sub.s]) was used to adjust the regression model for in situ conditions. Variances and correlations in the regression models are presented. CE Database subject headings: Soil properties: Dynamic properties; Organic matter; Peat; Shear modulus; Damping; Regression models.