Liquefaction potential of sand tailings dams evaluated using a probabilistic interpretation of estimated in-situ relative density

Abstract

In Chile, sand tailings dams represent the most common deposits of mining residues. These structures present a potential risk in terms of mechanical instability due to their potential susceptibility to seismic liquefaction. In order to manage these risks, it is necessary to take a probabilistic approach, thus accounting for inherent variability of material properties. However, in practice, implementing such an approach is impeded by the difficulty of acquiring and managing the data to be used in the reliability calculations and is conditioned by the relevance of the probabilistic models chosen to represent this variability. This paper proposes a method for onsite determination of the tailings relative density (DR%), and its variability, using dynamic penetration tests. This method was applied to typical Chilean sand tailings dams, and proposes a single model for all such tailings dams by associating a probability model to the variation of DR%. Finally, the validity of this approach is demonstrated by performing a reliability calculation of liquefaction potential (which is the main cause for the failure of this type of structure in this country) for a particular sands tailing dam.Keywords: cone penetrometer test; relative density; liquefaction; sand tailings dams. ResumenEn Chile los tranques de arenas de relaves representan los depósitos de residuos mineros más comunes. Estas estructuras presentan un potencial riesgo en términos de inestabilidad mecánica debido al fenómeno de la licuefacción sísmicamente inducida. Para conocer este riesgo, es necesario considerar una aproximación probabilística. Sin embargo, en la práctica, la implementación de estas aproximaciones es muy limitada, debido la dificultad obtener los datos necesarios para los cálculos de fiabilidad, y a la selección de los modelos probabilísticos necesarios para representar su variabilidad. Este artículo propone un método para estimar in-situ la densidad relativa (DR%) en arena de relaves y su variabilidad, a partir de ensayos de resistencia a la penetración dinámica. El método se aplica en tranques de arena de relaves chilenos, proponiendo un único modelo para la función de probabilidad del parámetro DR%. Finalmente, el interés de esta aproximación se demuestra mediante un cálculo de fiabilidad del potencial riesgo de licuefacción, correspondiente a la principal causa de falla en países sísmicamente activos como Chile.Palabras claves: ensayo de penetración, densidad relativa, licuefacción, tranques de arenas de relaves.9

Prior and future earthquake effects in Valdivia, Chile

“…Liquefaction occurs in soils that are granular and controlled mainly by gravity and not by colloidal forces, therefore a plasticity index PI of less than 8 to 12. The same has been found in the liquefaction potential analysis of tailings dams, commonly used in Chile (Villavicencio et al, 2016).…”

Liquefaction potential sand-silt mixtures under static loading

“…Many probabilistic approaches exist (Villavicencio, Breul, Bacconnet, Fourie, & Espinace, 2016), but in practice, the implementation of such an approach is difficult. On the other hand, new evidence indicates insufficiency and a certain deviation from these Chinese criteria with respect to the presence of fines.…”

Liquefaction potential of upstream tailings dams using a nonlinear elastoplastic constitutive model

“…After calculating the cyclic resistance ratio, the cyclic stress ratio as the driving factor is calculated using Eq. 14 (Villavicencio 2020):…”