Augmented slope stability analysis approach to determine setback distance based on target factor of safety criteria

ABSTRACT: Determination of setback lines for developments along river valley and ravine slopes continues to be a challenge for engineers. In particular, two tasks include consideration of long term processes in the slope stability model, and selection of a reasonable slip surfaces for a non-critical factor of safety (FOS). The conventional approach, which uses long term soil parameters (zero or near-zero cohesion) directly in the slope stability model, may result in conservative setback distances due to unreasonable slip surfaces. In this paper, an augmented approach is presented, which uses present soil parameters (non-zero cohesion) in the model to determine reasonable trial slip surfaces. Subsequently, the impact of long term processes is considered on these slip surfaces to determine a long term, non-critical FOS, upon which optimized setback distances can be determined. In general, the augmented approach is an attempt by the authors to provide a starting point for further refinement of setback distance determination methods that are based on FOS criteria.