Simulation of deep excavations using finite element method

Abstract

Finite Element calculations arc frequently utilized for the design of deep excavations because a prediction of ground movements and wail deformation is not possible with classical limit equilibrium methods. To solve such Geotechnical boundary value problems, appropriate constitutive laws are necessary for the description of mechanical behaviours of soils. The possible combinations of these behaviours are divided into two groups; those with a constitutive law based on plasticity and those without. The latter group contains linear elasticity and variable elasticity. A key distinction between the plasticity and the elasticity group is that in latter, strains are recoverable upon decreases in stresses, where as elastoplastic models strains are only partly recoverable. A crucial point in determining the choice of a suitable soil constitutive model is the ease with, which values can be assigned to the constants defining it. With considering those pointed above, this paper summarizes the application of simplest linear elasticity analysis for convenience for modeling 15m deep base excavation supported with bored pile wall. Finite element software GEO SLOPE/SIGMAW DEFINE is applied for 2-D plain strain analysis. The mechanical behaviour of the soil is modeled with linear elastic constitutive model using reasonable soil parameters. Excavation was carried out in 4 steps, pre-stressed anchors were used as additional supports, just before each excavation step. The FEM simulation was carried out to compare the computed and observed pattern.