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3D Seepage modelling in tailings storage facility analysis and design for low permeability lined basins

Wesley Rouncivell, Sheila Imrie, Graham Howell and Adriaan Meintjes
Wednesday, February 12, 2020
First presented: 
SAIMM Tailings Storage Conference
Published paper
Mine Waste

Tailings Storage Facility (TSF) stability is significantly affected by the pore pressures in the outer embankments. As more TSFs are using low permeability basin barrier systems for environmental compliance, the potential for mounding of the phreatic surface, with the associated increased stability risk, needs to be understood. Three-dimensional (3D) seepage modelling supports two-dimensional (2D) analyses and provides additional insight in cases where the internal drain geometry cannot be represented accurately using 2D cross-sections. Two case studies with HDPE lining systems are presented. The first is an existing TSF where tonnage creep and excessive water storage on the TSF have led to high phreatic levels. A calibrated 3D model was developed to access different drain design interventions. The second case study is a new TSF where an extensive footprint drainage network, supplemented by a vertical curtain drain, has been designed to minimise not only the location of the phreatic level but also the rate of pore pressure build-up with depth to significantly below hydrostatic.

This paper presents case studies from existing projects; the scenarios presented were chosen to demonstrate the usefulness of the 3D modelling and are not necassarily the final designs adopted for the respective projects.

SRK Africa