Resonant column testing of sands with different viscosity pore fluids

The effect of pore fluid viscosity on the stiffness, damping, and liquefact ion characteristics of sands was investigated to assess the potential contr ibutions to a centrifuge model seismic response for soils saturated with hi gh-viscosity pore fluid. Resonant column tests with cyclic loading frequenc ies in the range of 20-45 Hz were performed on a variety of fluids and sand sizes. At a strain level less than 7, x 10(-4), the damping increased with pore fluid viscosity and shear strain amplitude, and it decreased with san d particle size. However, at shear strain greater than about 2 X 10(-4), th e increased skeleton damping tended to mask any effect of additional dampin g due to fluid viscosity. The liquefaction tests on fine silica sand reveal ed that the increase in total energy dissipation was not more than 10% for 100 cS oil when compared with water at a driving frequency of 25 Hz. Based on the experimental results, a simple model is proposed to examine the depe ndency of viscous damping on pore fluid viscosity, loading frequency, parti cle size, and shear strain amplitude.