Reliable Design with Limited Data: Characteristic Strength Selection for Slope Stability Assessment

May 6, 2026

The selection of characteristic shear strength values for slope stability assessments of tailings storage facilities (TSFs) requires careful consideration of uncertainties in material properties, arising from both spatial variability and the inherently limited scope of site investigations. When sample size and layer geometry are not explicitly considered, the resulting design values may not reliably represent in-situ conditions. This paper demonstrates an approach to deriving characteristic shear strength values that incorporates sample size and layer geometry in accordance with Eurocode 7 (EN 1997). A case study is presented using twelve monotonic simple shear tests on a TSF foundation soil. From this data, a design value for the undrained shear strength ratio (su/σ′v) is obtained by both conventional means and through a procedure guided by the 2nd Generation EN 1997. Comparisons between the two approaches highlight the sensitivity of strength selection and emphasise the importance of appropriate statistical treatment when defining characteristic values. The influence of each approach is further demonstrated through its impact on the stability of a simplified slope. The findings illustrate a structured method for selecting characteristic su/σ′v values that balances limited data with explicit uncertainty treatment, supporting more reliable and defensible design decisions in TSF stability assessment.

Brandao, H.A., Kirsten, L., Duque, R., Delport P., Jibiki, T., Fourie, A. 2025 " Reliable Design with Limited Data: Characteristic Strength Selection for Slope Stability Assessment,” in Proceedings of the SAIMM Tailings Conference 2026, 3-4 March 2026, Johannesburg, South Africa: South African Institute of Mining and Metallurgy (SAIMM)