T.E. Martin, E.C. McRoberts: Some considerations in the stability analysis 1 Some considerations in the stability analysis of upstream tailings dams

ABSTRACT: Upstream constructed tailings dams represent a significant challenge to the geotechnical engineer in terms of analysis of their stability, in large part because the shear strength of the loose sands and fine grained or “slimes ” components of such structures is open to considerable uncertainty. In particular, it is critical that the behavior of the tailings under shear (contractant or dilatant, failure under drained or undrained conditions) be understood, and that this understanding be incorporated into stability analyses. The continued development of critical state soil mechanics has served to focus attention on this issue, but this focus has generally been directed towards problems involving seismic liquefaction. However, contractant versus dilatant behavior in shear is equally important in terms of static stability, particularly for upstream tailings dams which so often are constructed of primarily contractant, potentially liquefiable materials. This paper presents a review of drained versus undrained methods of static stability analysis of upstream tailings dams, and how these relate to dilatant versus contractant behavior. The authors support the view that for upstream dams constructed of contractant, potentially liquefiable tailings, both undrained strength analysis and steady state strength analysis should be considered, and that effective stress analysis for such structures can be fundamentally incorrect and unsafe.