Failure of the Embankment Foundation (Studies on the Failure and the Settlement of Foundations)

Abstract

For the stability computation of so-called embankment type structures such as an earth dam, levee and railway embankment built on a soft foundation, it is necessary to have a comprehensive knowledge as to the rupture phenomena of the earth foundation during the consolidation of soft clay. In this paper, taking the standpoint that the pore water pressure, which has the dengerous effect on the stability of the foundation during or just after the fill construction, must be diminished by the adequate control of execution speed, a theoretical treatment is performed to clear the mechanism of the plastic flow of the foundation containing the pore water pressure, whose distribution is determined in the following way. Starting from the fundamental theoretical equation of the two-dimensional consolidation, the research is performed for the foundation which has infinite depth or under which a perfectly rigid and smooth rock base exists at any depth. First, applying Neuber's theory of elasticity, the stress distribution just after loading is obtained, and using this as the initial condition, the solution of the consolidation equation is represented in the form of Fourier's integral or Fourier's series with regared to each boundary condition. Next, performing the numerical calculation for the case of a uniformly distributed load, the pore water pressure is computed as to the sudden loading and also as to the gradually increasing load on the semi-infinite foundation with an allowable precision. It is also shown that such a solution is obtained for the foundation where the permeability is different in its vertical and horizontal directions, and for the case of parabolic load whose distribution is closer to the actual dam foundation. Comparing the results of these calculations with each other, the change of the distribution of the pore water pressure in respect to situation and time is studied for each loading condition.