ABSTRACT
Sweden and Finland on which European design guidelines are based (EuroSoilStab, 2002).
Numerical methods, such as finite element (FE) analysis, can be used as an alternative to conventional design methods. They are particularly suitable for serviceability limit state design. FE analyses allow adopting advanced constitutive models that take the complex stress-strain behaviour of natural soil and stabilized columns into account. The problems involving a grid of circular columns under an embankment or a strip footing are fully three-dimensional problems. As 3D analyses are computationally very expensive an enhanced 2D technique using the so-called volume averaging technique is adopted. The basic idea is to describe the column-improved ground as a homogenized composite material and map the true 3D problem into 2D. Once the constitutive relations of both composites are defined, the response of the column improved ground can be studied in two dimensions subject to arbitrary loading and boundary conditions. Within the volume averaging technique two advanced constitutive models for soft soil and deep mixed column were implemented: the S-CLAY1S model (Karstunen et al., 2005) to represent the soft soil and the MNhard model (Benz, 2007) to represent the deep mixed columns. In principle any elasto-plastic constitutive model can be applied for either of the two constituents.
