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

酸性尾矿储存设施的回收是采矿业面临的一项挑战。传统的方法被重新审视，以纳入气候变化、资源稀缺和负责任的采矿等问题。在过去十年中，将惰性尾矿(即通过脱硫而变得不具活性的尾矿)重新用作回收方案中的覆盖材料一直是研究的重点。矿业公司现在认真考虑将脱硫回收作为负责任的矿山开发的一部分。然而，在生产覆盖材料的矿场作业中，脱硫并不经常使用。在加拿大的几个地点全面实施了将脱硫尾矿作为单层覆盖物的工作。在全尺寸覆盖物上发现了挑战，主要与脱硫尾矿硫含量和粒度分布的变异性有关。事实上，在以泥浆形式水力沉积的覆盖层上，会出现明显的粒度分离，这可能会影响覆盖层的性能。此外，脱硫尾矿作为覆盖材料可能会在其使用寿命内发生变化。由于盖层内残留硫化物的消耗，可能发生地球化学演化。其他元素可能会随着时间的推移从盖子中释放出来，并影响流出物的质量(例如锌、砷)。被覆盖的硫化尾矿中的新条件，在防止硫化物氧化的同时，可能会引发其他反应，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属性对覆盖性能进行了初步评估。对覆盖物性能的长期观点需要包括覆盖物材料性能的变化，特别是用作覆盖物材料的脱硫尾矿，因为复垦场地的使用寿命是不确定的。作为覆盖材料的脱硫尾矿即将全面实施，作为一种成功的回收方案。该研究方案旨在通过三个主要目标填补与覆盖物异质性和演变对长期性能影响有关的知识空白：(1)考虑化学成分和颗粒分布的异质性和空间变异性，从二维和三维建立脱硫尾矿覆盖物系统水文地球化学行为的数值模型；(2)评估脱硫尾矿覆盖物系统的中长期性能，考虑产酸尾矿和脱硫尾矿覆盖物中地球化学条件的演变；(3)将脱硫尾矿覆盖物系统的行为从实验室结果和数值预测与全尺度覆盖进行比较。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。在该研究项目的整个过程中，预计将培训1名博士、1名硕士、1名PDF和3名实习学生。

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.