The role of capillary water in the stability of tailing dams

Tailings storage facilities are complex geotechnical structures. The present paper focuses on the study of a case-history, a tailing dam from the nickel industry located in Cuba, with the objective of gaining knowledge about the geotechnical behaviour of such structures. The dam behaviour was modelled by means of a coupled hydro-mechanical finite element formulation. Due to the low permeability of tailings, the phreatic surface in the deposit remains high during and after its construction. Steady-state flow regime would be reached only several decades after closure. Moreover, capillary rise causes the saturation degree to stay high in the whole storage. Under the action of rain storms, phreatic levels rise quickly due to the presence of capillary water. Following the end of the storm, phreatic levels fall slowly because of the low hydraulic conductivity. The results of the analysis show that the stability of the dam strongly depends on capillary phenomena. In the light of this conclusion it seems reasonable to propose including the measurement of capillary water in the standard monitoring schedule of tailing dams.