Chimney Drains to Control Seismic Pore Pressures

Abstract

To control the earthquake-induced pore pressures in earth dams with pervious gravelly shells, a method is presented to design chimney drains to be installed in the upstream part of embankments. Essentialy, it consists of determining the maximum breadth, B, between an impervious layer (or a flow dividing surface) and a highly pervious drain, along which the dynamic pore pressure ratio can be maintained below a pre-established value during the earthquake. The variables involved, time factor, time interval to dissipate earthquake-induced pore pressures, compressibility and permeability, are examined.