Seismic Response and Liquefaction of Sands

An effective stress analysis has been developed for determining the dynamic response of horizontal saturated sand deposits to earthquake motions consisting of vertically propagating shear waves. A hyperbolic stress-strain law is used for sands in shear and during the earthquake motions the modulus and damping properties of the sands are modified continuously for the effects of dynamic shear strains and pore-water pressures. The pore-water pressures are continuously updated using equations which relate pore-water pressures to dynamic shear strain history. Comparisons between data from the effective stress analysis and current total stress methods show that only the effective stress method can predict and reproduce the phenomena that occur in saturated sands during earthquakes. It gives the time to liquefaction, the time history of the development of pore-water pressures and surface accelerations comparable in form to those recorded on saturated sands during earthquakes.