Damping Ratio for Dry Sands

Using the Torsional Simple Shear Device, the writers investigated the relationship between damping ratio λ and shear strain γ for Ottawa, Del Monte, Golden Gardens, and Seward Park sands. Experimental results show that the type of sand, as expressed in soil gradation and angularity, influences soil damping. However, this influence can be taken into consideration by introducing a soil gradation and sphericity factor, F, which is a function of the coefficient of gradation and soil sphericity. The writers propose an equation relating the damping ratio to shear strain as a function of the confining pressure, β^c, and soil gradation and sphericity factor F. A nomograph is proposed to assist in the easy determination of the damping ratio for sands.