Slope Stability Analysis

Slopes are always a source for bad surprises for the geotechnical community. Especially in cases where rapid or brittle failure may be suspected, it is essential to assess the stability of the slope in a reliable and timely fashion. In that regard, we have implemented in-situ testing procedures to acquire relevant deformation and strength parameters on the subsoils to model the slope and provide reliable factors of safety (FOS).

For the direct assessment of stability of an existing slope, our in-situ dilatometer testing (DMT) is a well suited and proven tool to determine both elastic parameters as well as strengths in a quasi continuous profile with depth. For the cases where the slope has failed or failure is imminent, we can obtain a direct measure of the residual strength of the soils along the main shear band by using borehole shear test (BST) procedures.

Once the subsoils conditions are determined, we use 2D limit equilibrium analysis to determine relevant FOS values. Our software for Limit Equilibrium analyses is Slope/w by Geo–Slope International, as the standard package in our geotechnical practice.

In addition, we perform 2D and 3D finite element analysis of slopes using the c–Φ reduction method. Although many geotechnical consultants are reluctant to rely in this class of slope stability analyses, we prefer its use, as they account for stress-strain compatibility of the soil mass during deformations.

In either methodology, the determination of reliable material properties is essential to complete a successful assessment of stability.