How to Prevent Flow Failures in Tailings Dams

Abstract

Based on research carried out at 67 tailings dams in Spain: (1) tailings dams contain alternating sedimentary layers with contractive and dilative geomechanical behaviours; (2) tailings saturate quickly but drain more than 10 times slower due to the high-suction capacity of the porous sediments (2–300 MPa); and (3) over the long-term, a stationary flow regime is attained within a tailings basin. Four temporal and spatial conditions must all be present for a tailing dams flow failure to occur: (1) the tailings must experience contractive behaviour; (2) the tailings must be fully saturated; (3) the effective stress due to static or dynamic load must approach zero; and (4) the shear stress must exceed the tailings residual shear stress. Our results also indicate that the degree of saturation (Sr) is the most influential factor controlling dam stability. The pore-pressure coefficient controls geotechnical stability: when it exceeds 0.5 (Sr = 0.7), the safety factor decreases dramatically. Therefore, controlling the degree of tailings saturation is instrumental to preventing dam failures, and can be achieved using a double drainage system, one for the unconsolidated foundation materials and another for the overlying tailings.

A Suggested Equivalent Method for a Drainage Structure to Analyze Seepage in Tailings Dam

“…Avoiding the failure of tailings dams has long been an area of focus for research [ 15 , 16 ]. After many summaries and investigations on tailings dam failures [ 16 , 17 , 18 ], seepage is considered one of the main causes of tailings dam failure [ 19 , 20 ].…”

“…After many summaries and investigations on tailings dam failures [ 16 , 17 , 18 ], seepage is considered one of the main causes of tailings dam failure [ 19 , 20 ]. Rodríguez et al [ 15 ] investigated 67 tailings dam failures in Spain. Enhancing drainage measurement was considered to be instrumental in preventing tailings dam failure.…”

Stability and Consolidation of Sediment Tailings Incorporating Unsaturated Soil Mechanics

“…In Equations ( 1) and ( 2), c c is defined as compression index whereas c s is defined as swelling index. In Sigma/W, it is possible to simulate the variations in the Young modulus (E ) as a function of effective stress using the elastic-plastic model (w/PWP Change) [18]. The Young modulus for incorporation in Sigma/W (under effective stress material model Elastic-Plastic) was obtained by first determining the coefficient of compressibility (m v ) from the oedometer test to determine the constrained modulus (E oed ) (Equation (3)).…”

“…Seepage, consolidation and stability analyses for sand tailing have been performed historically by either assuming that the soil to be completely dry, or the entire fill layer undergoing consolidation [17]. Ito and Azam [18] developed a 1-D consolidation model to estimate the behavior of sand tailing during the filling process. However, this method does not take into account the unsaturated soil mechanics principles during the construction of sand tailing.…”

Static Liquefaction Causes the Flow Failure of a Tailings Dam: A Case Study of El Descargador, Cartagena–La Unión Mining Region, SE Spain (October 1963)

“…Catastrophic mine tailings dam failures are increasing globally [2][3][4][5][6][7][8][9][10][11][12]. However, while the study of its ecological and socioeconomic consequences has been widely addressed in the literature [11][12][13][14][15][16][17] studies, attempts to address the hydro-geomechanical factors that caused the failures are scarce [18][19][20]. There is still more uncertainty regarding historical failures of dams that happened many decades ago, as is the case of El Descargador.…”