Tailings and Mine Waste Conference

Strength gain of fine tailings/slimes resulting from secondary compression Contreras, I.; Schimpke, K.; Ver Strate, R.


The offset upstream construction method consists of constructing tailings impoundment dams on top of previously deposited fine tailings/slimes. The undrained shear strength of iron ore fine tailings/slimes underlying offset dams has been observed to increase over time, which is referred to as strength gain. The strength gain consists of two components: (1) increase in undrained shear strength due to increasing confining stress from fill placement and (2) increase in undrained shear strength under constant effective stress, which occurs after the end of primary consolidation (EOP). The second component of strength gain can be explained using the secondary compression concept. This paper presents field and laboratory testing used to characterize the strength gain of fine tailings/slimes due to secondary compression. Results of cone penetration test (CPT) soundings in addition to laboratory vane shear and consolidation tests are presented. Findings based on this testing are described, and recommendations for implementing strength gain due to secondary compression in tailings dam design are included.

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