Dynamic Properties of Organic Soils

Abstract

AbstractA database of laboratory stiffness degradation data of 30 samples, cering a wide range of soil types and percentage of organic content, was assembled to allow a thorough investigation of the dynamic properties of organic soils. The collated datasets are first compared with existing, commonly used empirical, hyperbolic stiffness degradation and damping curves, which are expressed mainly as a function of plasticity index and effective confining pressure. The identified discrepancies between the collated data and the empirical curves of the literature were ascribed to the presence of organic matter, leading to the introduction of a new shape variable through nonlinear regression. Based on statistical analysis of the collated information a new empirical model for organic soils is proposed, describing the reduction of normalised shear modulus and variation of damping ratio with cyclic shear strain as function of organic content in addition to other key parameters (mean effective confining pressure, plasticity index, number of cycles and loading frequency). The proposed empirical model can be used in engineering practice to infer the dynamic properties of organic soils in the absence of site-specific data.KeywordsOrganic soilsStiffness degradationDampingPeat