Strength and stiffness characterization of clays using Atterberg limits

Abstract

Atterberg limits are index parameters that can be determined using simple, inexpensive, and rapid laboratory tests. These limits are commonly used for the classifications of fine-grained soils. They may be also utilized in the preliminary assessment of strength and stiffness parameters of these soils, particularly at the initial phases of geotechnical investigation programs, ahead of conducting more advanced tests on undisturbed samples. Numerous studies in the geotechnical literature have been directed towards enhancing the relationships between Atterberg limits and the different mechanical parameters of fine-grained soils. However, there is still a necessity to improve the accuracy and applicability of such correlations. In this study, the undrained rigidity index is correlated with the plasticity indices using a comprehensive worldwide clay database. Subsequently, the effective friction angle is determined using an expression of the rigidity index derived from the Critical State Soil Mechanics. New formulations are developed for the undrained shear strength under compression, extension, and simple direct shear modes, as well as expressions for the constrained, shear, and Young’s elastic moduli. The deduced formulations are validated using the results of the geotechnical investigations for well-reported sites. A close agreement is demonstrated between the measured and the estimated parameters, implying that the proposed approach is broadly valid and applicable.