Dynamic stiffness and damping of four compacted clays at different consistencies from resonant column tests

Compacted clays are used in the construction of embankments, dam cores, and landfill sealings. Dynamic stiffness and damping, dependent on the confining stress and shearing strain amplitude, are required in the seismic analysis of such geotechnical structures. A series of multi-stage tests were conducted in a conventional fixed-free resonant column device to determine these material properties for four clays. A compaction state corresponding to optimum water content at Proctor density was used as a reference. The water content was subsequently modified to reproduce a 3 % drop in density. Soil-water characteristic curves were obtained using different techniques depending on the suction level. The clays were tested to assess the effect of the consistency state on the dynamic soil properties over wide strain ranges at different confining stresses. Besides the shear modulus, the small-strain Young's modulus was measured in the flexural vibration mode. The effects of suction on the small-strain shear modulus are discussed. Design equations in terms of total stresses are provided for use in practice. • Four different compacted clays are investigated with respect to dynamic properties. • Effects of the degree of saturation and consistency are assessed. • Total stress exponent for small strain stiffness is smaller than for saturated natural clays. • SWCC are determined to assess suction and effective stress dependence of stiffness. • Equations for moduli and damping over wide strain ranges are derived for use in design.