ATIENUATION AND PHASE DELAY OF DYNAMIC PRESSURE IN SAND ZONE OF VARIOUS POROSITY

Abstract

Zen et al (1987) has derived a well-known equation on the dynamic behavior of pore water pressure in the study on the mechanism of wave-induced liquefaction and densification in a permeable seabed. As a result, they reveal that pore water pressure attenuates its magnitude and delays its phase during its propagation into permeable seabed and that these phenomena are highly related to the physical properties of seabed such as permeability, porosity and volume compressibility of seabed sand.This study intends to clarify the effects of porosity on the attenuation and phase delay. A series of model tests reveals that period of the dynamic pressure loaded on the surface of seabed is a controlling factor for both attenuation and phase delay and that a firm power functional relationship exists between the attenuation rate and porosity of seabed sand although a clear effect of the porosity is not found in the case of phase drift.