Infiltration in a novel unsaturated multi-layered cover system for use in tailings storage facilities
Loading...
URL
Journal Title
Journal ISSN
Volume Title
School of Engineering |
Master's thesis
Authors
Date
Department
Major/Subject
Mcode
Language
en
Pages
67
Series
Abstract
Conventional barrier systems in tailings storage facilities often rely on thick monolithic geomaterials (1.5 m-2.5 m) or geosynthetics that fail under ex-treme precipitation or snowmelt events typical in Nordic climates. This study proposes and evaluates a novel, fully unsaturated multi-layered cover system (MLCS) constructed majorly from on-site sourced tailings and waste rock. The tailings are modified through either mixing with biochar and clay or by altering surface polarity to make them functional components of a newly conceptual-ized MLCS. The MLCS design integrates capillary barrier mechanisms with a water-entry-head-controlled hydrophobic interface to act as a final hydraulic buffer during extreme ponding conditions. Laboratory characterization of soil-water retention curves (SWRCs), unsaturated hydraulic conductivity functions (SHCFs), and hydrophobicity confirmed the enhanced water-buffering capaci-ty of the modified tailings mixtures. Especially, the threshold-based break-through resistance of the hydrophobic layer (WEH ≈ 4.71 kPa) allowed the construction of an overall thin MLCS (≤0.5-m-thick). This MLCS was physically modelled in an instrumented 1-D column subjected to a ponding head equivalent to a 500-year rainfall event. Results showed complete suppression of percolation below the MLCS for 61 days of testing period, with the hydro-phobic layer preventing breakthrough even after upper layers neared saturation. Complementary two-stage finite element simulations, incorporating WEH-triggered hydraulic switching, accurately reproduced observed suction, water-content, and percolation behaviour. The findings demonstrate that the proposed MLCS provides a climate-resilient, all-weather hydraulic barrier, reduces dependence on imported materials, and offers a feasible, low-cost closure strategy for Nordic TSFs. Further work should assess performance under field-scale slopes including lateral drainage conditions.Description
Supervisor
Bordoloi, SanandamThesis advisor
Iravanian, AnooshehWijepala, Udesh