The dissipation of pore-water pressure in the embankment is largely influenced by the permeability and the storage characteristic of the embankment materials.
The lag of the phreatic line depends on factors such as: permeability of soils, drawdown rate, drawdown ratio and slope gradient during rapid drawdown, the stabilizing effect of the water on the upstream face is lost, but the pore-water pressures within the embankment may remain high.
Seed and Booker (1977) approach for pore-water pressure generation and dissipation is applied, with some modifications for evaluating the densification effect of GPs, incorporating modifications in coefficients of volume change and permeability, to the analysis of columnar gravel drains under a variety of earthquake conditions.
If the magnitude of pore-water pressure generated equals the confining pressure, the effective stress becomes zero, the soil is said to have liquefied.
Theory of pore-water pressure generation and dissipation developed by Seed and Booker (1977) is applied, with some modifications for evaluating the densification effect of RGPs, to the analysis of columnar gravel drains under a variety of earthquake conditions.
g] = peak excess hydrostatic pore-water pressure generated by the earthquake; and
So the excess pore-water pressure in the drain is effectively zero i.
e average of pore-water pressure generated over an initial cycle interval, dN.
Thereafter it decreases as pore-water pressure dissipates.
Each plot also includes a subsurface drain that can be used to control groundwater in the near-streambank vadose zone, supplementing existing research at OSU on the role of pore-water pressures
and groundwater processes on stream-bank erosion anci failure.