This article presents results from a laboratory investigation into the dynamic characteristics of reconstituted and undisturbed cohesive soils by means of resonant-column tests. In particular, results showing the influence of various soil parameters, such as confining stress, overconsolidation ratio, void ratio, plasticity index, calcium carbonate content, and time of confinement on shear modulus and damping ratio at small and high shear strains are presented and then discussed. Relationships for the small-strain shear modulus, the degradation of shear modulus at high strains, and the increase of damping ratio at high strains over its small-strain value are proposed. Finally, the practical implications of the results in the context of seismic site response analysis are discussed.

The paper presents results from a laboratory investigation into the dynamic properties of natural intact and model organic soils by means of resonant-column tests. The natural intact organic soils were sands, cohesive soils and peats with varying content of calcium carbonate. The model organic soils were formed in laboratory by mixing kaolinite and paper pulp. The influence of various soil parameters, such as strain level, confining stress, void ratio, plasticity index, organic content and secondary consolidation time on shear modulus, G, and damping ratio, DT, is presented and discussed. The test results on natural organic soils show that only high organic contents (OC C 25%) have significant influence on G and DT at both small and high shear strains. For the model organic soils, however, a significant influence of even lower values of organic content (5% B OC B 20%) on G at small strains and DT at both small and high strains is observed.

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This article presents results from a laboratory investigation into the cyclic and dynamic properties of soils from Düzce, Turkey, conducted after the destructive November 12, 1999 earthquake. The investigation was mainly conducted by means of monotonic and cyclic triaxial, as well as resonantcolumn tests. The triaxial tests allowed the determination of the liquefaction resistance of silty sands, as well as their critical state behavior, whereas the resonant-column tests allowed the determination of shear modulus and damping ratio of cohesive soils. The results are presented and then discussed together with their pertinence to soil behavior when subjected to earthquake loading.