Mechanical Response of Tailings Under Monotonic Triaxial Tests in Unsaturated and Nearly Saturated Conditions

A detailed knowledge of the mechanical behaviour of unsaturated tailing wastes is a key element to assess the stability analysis of tailing facilities, considering the variation of the soil strength due to climate effects, rainfall, or poor management in order to minimize the high rate of recent failures associated with unacceptable fatalities, economic and environmental damages. This research investigates the mechanical behaviour of unsaturated fluorite ore wastes collected after the failure of the Stava tailing dams (Italy). The static liquefaction response of the tailings was studied by carrying out CIU triaxial tests by through application of different backpressures to obtain unsaturated or nearly saturated specimens. The influence of the degree of saturation on the mechanical response of Stava tailings is investigated and the static liquefaction strength evaluated. Outcomes are interpreted based on the Water Retention Curve estimated by performing water retention tests on the same soil, and within the Critical State framework. Results are also compared with those obtained in fully saturated conditions from a previous experimental campaign.