A comparative study of critical failure surface determination in slope stability assessment

Abstract

Slope stability analysis and design of manmade slopes has always been a challenging geotechnical problem. Different methods have been developed and created to examine two and three dimensional slope models based on various methods of assumption and assessment. Throughout this study two limit equilibrium, and finite element methods has been used to examine the stability of the slope and to determine the critical slip surface of failure by using PLAXIS, FLAC/Slope and SLOPE/W software programs respectively. Different values of shear strength parameters were chosen to investigate the efficiency of these methods. Various values of unit weight, cohesion, internal friction angle, and their impact on the safety factor were examined. Comparing the results for factor of safety indicated that finite element calculation used in PLAXIS gives more conservative results by 0.5% compared to SLOPE/W program. FLAC/Slope was observed as the most complicated software and finite difference method generally gave the lowest value for factor of safety in comparison with the other methods. Impact of internal friction angle, unit weight, and cohesion on length of failure arc was also evaluated, and no significant relation between length of failure arc (La) and safety factor was detected.