Numerical study of the factors affecting the consolidation of clay with vertical drains

Abstract

A methodology has been developed for the consolidation analysis of a unit cell of clay around a single vertical drain. An elasto-viscoplastic constitutive model has been used to capture the time dependent consolidation behaviour of clay. The model considers a void ratio rate dependent yield stress to separate pre- and post-yield consolidation processes. The governing equation of the consolidation of clays with vertical drains has been solved using a robust finite difference scheme. A parametric study has been conducted to identify the influence of viscosity and smear on the consolidation process. It has been shown that viscosity has minimal influence on the consolidation process for closely spaced drains whereas its effects are significant for largely spaced drains. The inner smear zone surrounding the drains was found to be the dominant factor in controlling the overall progress of consolidation. Even small sizes of the smear zone significantly can retard the progress of consolidation. The permeability within the inner smear zone has been found to be more important than its extent. A linear variation of permeability within the inner smear zone using the coefficient of permeability of the undisturbed soil and the remolded soils has been shown to capture the important effects of smear on consolidation.