Loading frequency effect on stiffness, damping and cyclic strength of modeled rockfill materials

This paper studies the loading frequency and waveform effects on shear modulus (G) and damping ratio (D) of three high compacted modeled rockfill materials by conducting large-scale triaxial testing. The laboratory test results have shown that the shear modulus, and especially the damping ratio behavior, is influenced by the frequency of loading. The excess pore water pressures generated in cyclic loading are less dependent on loading frequency, and most dependent on imposed strain level. The G and D values for sinusoidal waveform are slightly higher than those for the triangle waveform. Moreover, the D value of rectangle waveform is considerably higher than sinusoidal and triangle waveforms. Results indicated that when induced double amplitude axial strain exceeds 0.1%, the effect of the number of cycles in degradation of cyclic strength is significant.A failure criterion for 100% pore pressure ratio for the dense rockfill materials (i.e. initial liquefaction) is developed based on 2% double amplitude axial strain in 15 cycles of loading.

► We study the loading frequency and waveform effects on shear modulus and damping ratio. ► Dry and saturated rockfill specimens in isotropic and anisotropic conditions were tested. ► Increase in loading frequency causes increase in shear modulus and damping ratio. ► Damping ratio of rectangle waveform is higher than sinusoidal and triangle waveforms. ► Dry specimen has higher shear modulus and damping ratio in comparison to saturated ones.