Estimation of "characteristic" shear strength parameters in slope stability analysis

Abstract

Geotechnical engineering considers the determination of characteristic values of ground properties as crucial because it helps guarantee the dependability and safety of projects, while also taking into account the uncertainties related to soil properties. Numerous countries have proposed their own guidelines for determining characteristic values in slope stability based on local conditions. These guidelines typically focus on determining the characteristic values of shear strength, cohesion c', and friction angle ϕ’. The current Hong Kong design standard on slope stability analysis is based on global factor of safety approach. To assess which of the two designs, global factor design or limit state design, is more appropriate for analyzing slope stability, a comparison is made between local and international practices. A novel statistical approach is suggested to account for soils that have either a large or small volume along the failure surface, as well as the various uncertainties involved in determining the characteristic shear strength. This technique is employed in two sources of slope local designs in Hong Kong, benchmarking exercises and real case designs. To ease the comparison between limit state design and global design, the over-design factor (ODF) calculated by SLOPE W is compared with the factor of safety (FOS). The findings indicate that directly comparing the shear strength values of the two designs is highly impractical. While simplifying the comparison to ODF and FOS is possible, it is not feasible to directly compare the two designs and determine which design is the most appropriate for slope stability analysis due to numerous objective factors.