Evaluation of geotechnical property variability

TLDR

Inherent variability and measurement error in geotechnical properties are addressed in a companion paper, while this study focuses on transformation uncertainty. To evaluate geotechnical variability on a general basis that will facilitate reliability‑based design procedures, the authors assess inherent soil variability, measurement error, and transformation uncertainty separately. The authors use a second‑moment probabilistic approach to combine uncertainties for design properties such as undrained shear strength, effective stress friction angle, in situ horizontal stress coefficient, and Young's modulus. The study provides guidelines for the typical coefficients of variation of common design soil properties based on test type and correlation type.

Abstract

To evaluate geotechnical variability on a general basis that will facilitate the use of reliability-based design procedures, it is necessary to assess inherent soil variability, measurement error, and transformation uncertainty separately. The inherent variability and measurement error are addressed in a companion paper, and transformation uncertainty is addressed herein. A second-moment probabilistic approach is applied to combine these uncertainties consistently based on the manner in which the design soil property is derived. The design properties considered in this paper are undrained shear strength, effective stress friction angle, in situ horizontal stress coefficient, and Young's modulus. This paper concludes with specific guidelines on the typical coefficients of variation for these common design soil properties as a function of the test type and the type of correlation used.Key words: transformation uncertainty, undrained shear strength, friction angle, in situ horizontal stress coefficient, Young's modulus, geotechnical variability.