Improving Slope Deformation and Stability Predictions in Anisotropic Rock Masses: A Strain- and Confinement-Dependent Dilation Model for Ubiquitous Joints
Authors: Farahmand, K.1, Rahjoo, M.2
Conference: Slope Stability 2026
Date: October 26–29, 2026
1 Knight Piésold, Vancouver, Canada
2 University of British Columbia, Vancouver, Canada
ABSTRACT
Open‑pit slope stability analyses rely not only on predicting failure but also on reproducing realistic deformation patterns for calibration against field monitoring data. In common numerical practice, uniform and low‑value dilation angles are adopted to constrain dilation‑induced volumetric expansion and the resulting displacement magnitudes in numerical models. This simplification overlooks the strong dependence of dilation on shear history and confinement stress, frequently leading to displacement fields that are inconsistent with prism and LiDAR measurements used in operational slope monitoring.
This paper presents a strain‑softening and confinement‑dependent dilation formulation developed specifically for ubiquitous joints in FLAC3D. The mobilized dilation angle is defined as a function of accumulated plastic shear strain and effective normal stress, allowing dilation to degrade progressively with shear and to be suppressed under increasing confinement. Comparative numerical examples demonstrate that the proposed formulation produces more realistic displacement gradients, localized deformation, and shallower failure mechanisms relative to constant‑dilation assumptions. These improvements enhance the ability to calibrate numerical models against monitored slope movements, supporting observational and performance‑based design approaches for the management of critically deforming pit walls.
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