The Effect of Impedance Drainage on Liquefaction of Sands

The occurrence of liquefaction in saturated sands has been investigated under small departures from the undrained condition. Volumetric deformation are inevitable in field problems on account of the spatial variations in excess pore pressures generated during the earthquake shaking and their subsequent dissipation after, considered together with the relatively high permeability of sands. The departures from the undrained mode were simulated in the laboratory by loading sand under the strain path control, that simulated, not only zero, but small finite amount of controlled volumetric deformations. It is shown that the undrained state of loading normally assumed during earthquake shaking may not represent the most damaging scenario with regard to liquefaction and instability.