Influence of desulfurized tailings cover heterogeneity and variability on long term performance of mine site reclamation

产酸尾矿储存库的回收利用是矿业面临的一个挑战。传统的方法被重新审视，以纳入诸如气候变化、资源稀缺和负责任的采矿等问题。惰性尾矿或经脱硫后不活泼的尾矿在回收方案中作为覆盖材料的再利用，是过去十年研究的焦点。作为负责任的矿山开发的一部分，矿业公司现在正在认真考虑脱硫复垦。然而，在生产覆盖材料的作业中，脱硫并不常用。在加拿大的几个地点全面实施了脱硫尾矿作为单层覆盖物。在全尺寸覆盖上发现了挑战，主要与脱硫尾矿硫含量和粒度分布的变异性有关。事实上，在水力沉积成泥浆的盖板上，会发生明显的粒度偏析，这可能会影响盖板的性能。此外，脱硫尾矿作为覆盖材料在其使用寿命期间可能会发生变化。由于覆盖层内残余硫化物的消耗，可能发生地球化学演化。随着时间的推移，其他元素可能从盖上释放出来，影响出水质量（如锌、砷）。覆盖硫化物尾矿中的新条件在防止硫化物氧化的同时，可能引发其他反应，导致金属的释放。以前的数值模拟使用不随时间变化的估计平均覆盖物属性提供了覆盖物性能的初步评估。对掩体性能的长期展望需要包括掩体材料性能的可变性，特别是用作掩体材料的脱硫尾矿，因为再生场地的使用寿命是无限期的。作为一种成功的回收方案，脱硫尾矿作为覆盖材料已接近全面实施。本研究旨在通过以下三个主要目标来填补覆盖层非均质性及其演化对长期性能影响的知识空白：(1)考虑化学成分和粒度分布的非均质性和空间变异性，建立脱硫尾砂覆盖层系统水文地球化学行为的二维和三维数值模型；(2)综合考虑产酸尾砂和脱硫尾砂盖内地球化学条件的演化，对脱硫尾砂盖系统的中长期性能进行评价；(3)将脱硫尾砂覆盖系统的性能与实验室结果、数值预测与全尺寸覆盖进行比较。将使用的方法包括实验室实验、现场仪器和测量以及数值模拟。预计培养博士1人，硕士1人，PDF 1人，实习学生3人。

Reclamation of acid generating mine tailings storage facilities is a challenge for the mining industry. Traditional methods are revisited to incorporate issues such as climate change, resource scarcity, and responsible mining. The reuse of inert tailings, or tailings made unreactive by desulfurization, as cover material in a reclamation scenario, has been a focus of research for the past decade. Mining companies now seriously consider desulfurization for reclamation as part of responsible mine development. However, desulfurization is not often used in operating mine sites for production of cover material. Full-scale implementation of desulfurized tailings as monolayer covers was performed on a few sites in Canada. Challenges were identified on full-scale covers, mainly related to variability of desulfurized tailings sulfur content and particle size distribution. Indeed, on a cover deposited hydraulically as a slurry, significant particle size segregation occurs, which could affect the performance of the cover. Furthermore, desulfurized tailings may evolve over their service life as cover material. Geochemical evolution may occur because of residual sulfide consumption within the cover. Other elements may be released over time from the cover and affect effluent quality (e.g. Zn, As). The new conditions in the covered sulfidic tailings, while preventing sulfides oxidation, may trigger other reactions leading to the release of metals. Previous numerical modeling provided preliminary evaluation of cover performance using estimated average cover properties that did not change with time. A long-term perspective on cover performance needs to include variability in cover material properties, and specifically for desulfurized tailings used as cover material, since reclaimed sites have an indefinite service life. Desulfurized tailings as cover material is close to being implemented at the full-scale level as a successful reclamation scenario. The research program aims to fill the knowledge gaps related to the effect of cover heterogeneity and evolution on long term performance through three main objectives: (1) Establish a numerical model of the hydrogeochemical behaviour of a desulfurized tailings cover system in 2 and 3 dimensions, considering heterogeneity and spatial variability in chemical composition and particle size distribution; (2) Evaluate the mid and long term performance of a desulfurized tailings cover system considering the evolution of geochemical conditions in the acid-generating tailings and in the desulfurized tailings cover; (3) Compare the behaviour of a desulfurized tailings cover system from laboratory results and numerical predictions to full scale cover. The methodology that will be used include laboratory experiments, field instrumentation and measurements, and numerical modeling. It is expected to train 1 PhD, 1 MSc, 1 PDF and 3 internship students over the course of this research program.