Tailings Liquefaction Analysis Using Strength Ratios and SPT/CPT Results

Abstract

Tailings dams constructed using the upstream method generally have relatively low- density materials with a high degree of saturation. Such conditions can generate the phenomena of liquefaction, which is potentially critical in slurry tailings disposal systems. Slope stability analyses involving liquefied soil require that the shear resistance of the softened soil be estimated and then, a good practical alternative is back-analyzed with field case studies involving slope failures, using commonly SPT and CPT results. The Olson (2001) and Olson & Stark (2003b) liquefaction analysis methodology based on strength ratios, included in this approach, is comprised of three stages: (i) liquefaction susceptibility analysis; (ii) triggering analysis; and (iii) post-triggering - flow failure stability analysis. In this paper, this approach was applied for stability assessments to verify liquefaction potential in an upstream tailings dam built by the hydraulic fill technique and located in the Quadrilátero Ferrífero (Iron Quadrangle) region, southeastern of Brazil. The results ratified the safety condition of the impoundment although they have demonstrated that the tailings tend to exhibit contractile behavior during shear, indicating liquefaction susceptibility.