On the influence of a non-cohesive fines content on small strain stiffness, modulus degradation and damping of quartz sand

The influence of a non-cohesive fines content on small-strain shear modulus Gmax, small-strain constrained elastic modulus Mmax, shear modulus degradation G(γ)/Gmax, damping ratio D(γ) and threshold shear strain amplitudes γtl and γtv has been studied in approx. 130 resonant column (RC) tests with additional P-wave measurements by means of piezoelectric elements. Specially mixed continuous grain size distribution curves of a quartz sand with varying fines contents (0≤FC≤20%, defined as the mass percentage of grains with size d<0.063mm according to DIN standard code) and uniformity coefficients (1.5≤Cu≤50) have been tested at different relative densities and pressures. A significant decrease of Gmax and Mmax with increasing fines content was observed, while the modulus degradation curves G(γ)/Gmax were found rather independent of FC. A pressure-dependent decrease of the damping ratio and a slight increase of the threshold shear strain amplitudes γtl and γtv with fines content were measured. Extensions of several empirical equations for Gmax, Mmax, G(γ)/Gmax and D(γ) considering the influence of the fines content are proposed in the paper.