Evaluation of Strength Parameters for Application in Cemented Iron Ore Tailings Stacks

The dry stacking of tailings, rather than the slurry disposal, is an alternative to overcome the safety related issues of the tailings dams and to reduce the space required for the tailings' storage. The addition of small amounts of cement into the tailings before the stacking may enhance the engineering properties of the material, enabling the construction of more inclined and higher mounts without compromising the pile's structural stability. The present research assesses the mechanical response of compacted iron ore tailings-cement mixes for dry stacking. Ultrasonic pulse velocity and unconfined compressive strength tests were carried out for a variety of 15 combinations of dry densities and amounts of cement, defined via a full factorial design setup. Then, drained standard triaxial tests were conducted for two dosages and three confinement levels (p'(0) = 50, 100, and 200 kPa). The results of unconfined strength and shear modulus were successfully correlated with the eta/C-iv, while the triaxial testing data have revealed further characteristics concerning the mechanical response of the artificially cemented iron ore tailings. Two methodologies have properly related the triaxial testing data to the unconfined compressive strength results permitting the determination of peak strength envelopes for specific dosages as a function of basic tests. So, the paper permits estimating c' and Phi' for a specific condition of porosity and cement content by unconfined compression results without carrying out triaxial testing or any other complex tests. This would be useful for viability studies and the pre-project phase of dry stacks.