Effect of Tamping Conditions on the Shear Strength of Tailings

Abstract

Moist tamping (MT) is likely the most common sample preparation technique used in the study of tailings, owing to the ability of MT to produce loose, contractive specimens. While the preparation of such loose samples to identify the critical state line is well established, MT is also frequently used to study trends of tailings behavior across a range of states. Preparation of dense states using MT may require significant compactive effort, the effects of which have not been studied in detail. A series of triaxial compression tests were carried out on two gradations of tailings to assess the effect of compacting to dense initial states on the resulting undrained shear behavior. This indicated that the process of compacting a specimen to a dense initial state may result in significant increases to peak undrained shear strength compared to samples prepared initially loose that achieved the same state at a range of consolidation stresses. This outcome emphasizes the importance of applying caution during sample preparation to avoid potentially unrealistic peak undrained strengths occurring during testing that are artifacts of the preparation procedure and unlikely to be relevant to in situ conditions.