General solutions for consolidation of multilayered soil with a vertical drain system

Abstract

A quasi-analytical method is newly introduced to solve the equal-strain consolidation problem of multilayered soil with a vertical drain system. Both vertical and radial drainage conditions are considered, together with the effects of drain resistance and smear. By using the method of Laplace transform with respect to time, a general explicit analytical solution for the consolidation in transformed space is obtained. Numerical inversion of the Laplace transform in the time domain is then applied to obtain the solution for calculating excess pore-water pressure. This solution is explicitly expressed and conveniently coded into a computer program for ease and efficiency of practical use. Its validity and accuracy are verified by comparing the special cases of the proposed solution with a finite-element solution and an available analytical solution. Moreover, the consolidation behavior of a four-layered soil with a vertical drain is investigated. The order of soil layers is shown to have a significant effect on the behavior of consolidation. This highlights that caution should be exercised when weighted average consolidation parameters of multilayered soil are used to analyze the consolidation behavior.