Understanding, characterization, modeling, and simulation of the spontaneous failure of tailings dams

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The extraction of raw materials goes hand-in-hand with the generation of large amounts of waste products, consisting of mineral solids, process water, and chemical substances. This often hazardous sludge, known as “tailings”, is pumped into massive earth ponds, so-called Tailings Storage Facilities (TSFs), which often achieve great dimensions. The failure of TSFs leads to an uncontrolled discharge of waste that may have catastrophic impacts on the environment and on human beings, and cause huge economic losses. Unlike dams for water storage, in which water can be discharged if its structural integrity is endangered, TSFs must stand in perpetuity. Nevertheless, the high rate of catastrophic failures worldwide - about 20 failures per decade in the past 60 years - demonstrates unambiguously that TSFs are far from fulfilling this requirement. The causes of TSF failures have mainly been geotechnical. Liquefaction, with static or dynamic triggers, is a major hazard threatening the stability of TSFs with extreme consequences. Inadequate understanding of the corresponding failure mechanisms in tailings is known as a major factor in tailings dam failure cases. There is, therefore, an urgent need to improve our fundamental understanding of the mechanical response of tailings under monotonic and cyclic loadings, our effectiveness in the characterization of tailings, and our capabilities in modeling and simulation of TSFs to assess their failure triggers, mechanisms, and precursors. This proposal responds to the urgent need to reduce the failure rate of TSFs. More specifically, building on the previous body of work developed by the applicant and his team of HQP in the two core areas of constitutive and numerical modeling of geomaterials, the aim of this research is to develop new solutions for the challenging problem of stability analysis of TSFs and their risk of failure. Understanding the liquefaction of tailings materials, predicting the onset of liquefaction, and modeling the behavior of liquefied and non-liquefied tailings are essential parts of this study. In particular, the study will include efficient constitutive modeling of tailings material and its numerical integration in versatile computational platforms, for sound mechanics-based modeling of tailings and TSFs to assess their stability and their risk of failure. The proposed research takes advantage of ongoing collaborations with leading industrial and academic institutes and will train 4 PhD and 2 MASc students who will be supported partially or fully by this NSERC DG as well as several undergraduate students, postdoctoral fellows, and visiting students from collaborating institutes who will be supported from other sources of funding. The short and long term outcomes of this research contribute to groundbreaking advances in the extractive industries' life cycle, increasing the sustainability of mining and generating added value to Canada.