4  Slope Stabilization With EPS Geofoam

4.3         Methods Of Analysis

4.3.1        The Limiting Equilibrium Method

GeoSlope software (GEOCOMP Corp., 1992) calculates the factor of safety and draws the slip surface of a slope. Soil Characteristics such as density, cohesion, and friction angle are required input for GeoSlope and other limit equilibrium methods of analysis.

Foam is idealized either as a stiff clay with very low density or the slope is treated as a bench neglecting the presence of the foam. Different magnitudes of horizontal seismic coefficients of horizontal seismic coefficients were applied to a range of earthquake magnitudes. Bishop circular option of analysis in GeoSlope was used in the parametric study.

4.3.2        The Finite Difference Analysis Method

Fast Lagrangian Analyses of Continua (FLAC) software (Coetzee et al., 1998) was used to analyze slope stability problems using the finite difference method. In the FLAC model, the cross section of the problem is divided into a mesh of preferably square elements. Mohr-Coulomb model is used to represent the soil. Cohesion, friction angle, dilation angle, density, shear modulus and bulk modulus are required input for the model.

Geofoam is represented in the model as an elastic material. Density, shear and bulk moduli were assigned for the elastic model. Values of these properties were chosen so as to cover the range of practical interest. The limits of the problem or boundary were selected to be sufficiently away from the region of critical slip surfaces. Failure was interpreted to initiate when the solution began to diverge. The safety factor of the cross section was calculated by dividing the shear strength of the soil by the shear strength at failure. The critical slip surface was defined by taking zones where the shear strain increment is maximum.