Abstract:
Depending on the stress state, mine tailings are generally accepted to be susceptible to static
liquefaction. A common method to assess the in situ stress state of tailings in relation to static
liquefaction susceptibility involves the use of the state parameter. Because most tailings materials
are normally consolidated (NC), this type of assessment requires knowledge about the
normal consolidation line (NCL). It has been shown experimentally that the uniqueness of the
NCL is vastly different for fine-grained and coarse-grained soils, with clays usually exhibiting a
unique NCL and clean sands exhibiting an infinite number of parallel NCLs. Gold tailings, a
sandy silt, fall between clays and clean sands, and there are limited experimental data regarding
their compression behavior over a range of initial void ratios. This lack of data results in
inconsistent interpretation of the uniqueness of the NCL for gold tailings in the industry. This
can influence the results of designs and safety evaluations of tailings dams. In this study, a
number of oedometer tests were conducted on gold tailings sourced from an active tailings
dam in South Africa. Several specimens were prepared at various initial densities and were
consolidated in small increments to a high effective stress. The oedometer tests were supplemented
with triaxial compression tests, from which a unique critical state line was identified.
Across the oedometer and triaxial tests, it was found that the behavior of the NC and overconsolidated
samples was consistent with that typically observed for fine-grained soils.
Therefore, for practical purposes, it appears that the gold tailings tested can be viewed in
a framework with a unique NCL. No significant influence of particle crushing was noted.
