Consolidated Undrained Shear Behavior of Synthetic Waste Rock and Synthetic Tailings Mixtures

• Published in: Geotechnical testing journal 2019-09, Vol.42 (5), p.1207-1232
• Main Authors: Hamade, Matteus M. P., Bareither, Christopher A.
• Format: Article
• Language: English
• ISSN: 0149-6115; 1945-7545
• DOI: 10.1520/GTJ20180007

The objective of this study was to evaluate the effects of mixture ratio (R) and synthetic tailings composition (i.e., particle-size distribution) on the undrained shear behavior of mixed synthetic waste rock and tailings (S-WR&T). Crushed gravel was used as a granitic waste rock (GWR), and mixtures of sand, silt, and clay were used to create average synthetic tailings (AST) and fine synthetic tailings (FST). Mixtures of S-WR&T were prepared to simulate coarse-dominated, optimal, and fine-dominated mixtures. Testing was conducted in consolidated undrained triaxial compression at target effective confining stresses of 10, 50, and 100 kPa. Coarse-dominated S-WR&T mixtures exhibited comparable shear behavior to pure GWR. Fine-dominated S-WR&T mixtures exhibited shear behavior that was more similar to pure synthetic tailings. However, an analysis of the undrained shear response indicated that the presence of GWR in fine-dominated S-WR&T mixtures can transition undrained flow behavior of pure synthetic tailings to limited-flow or no-flow behavior that is representative of GWR. The AST mixture prepared at optimal mixing conditions yielded an effective stress friction angle (φ′t) = 48°, and fine-dominated mixtures of AST yielded φ′t = 44°. The fine-dominated mixtures for FST yielded φ′t ranging from 32° to 38°, whereby φ′t increased with an increase in the amount of GWR in the mixture.