Finite element modelling of prefabricated vertical drains using 1D drainage elements with attached smear zones

Abstract

Prefabricated vertical drains (PVDs) are frequently used to accelerate the dissipation of excess pore pressures in low permeability soils subjected to load from overbearing structures, such as embankments. However, it is well known that the installation of PVDs leads to the formation of a smear zone in the surrounding soil, which will have a reduced radial permeability that hinders the flow of pore water towards the PVDs. It is essential that the smear effect be taken into account for estimating the rate of consolidation, but setting up finite element models which capture the geometry of many individual PVDs and smear zones involves building complicated meshes. In this paper, a new simulation tool is introduced which involves the attachment of a smear zone to drainage elements, allowing automatic reduction of the radial permeability at mesh integration points that fall within the smear zone, together with consideration of non-uniform hydraulic properties. This saves the analyst having to set up multiple separate regions within the mesh to capture smear effects, at no expense of accuracy.