New disposal techniques for reactive mine wastes to improve stability and facilitate site reclamation upon closure

安全管理大量活性矿山废物所面临的复杂挑战要求采取创新办法，解决各种地质环境问题，确保处置场的地质技术和水文地球化学稳定性。最近的工作表明，废石夹杂物（WRI）放置沿着尾矿库内的选定路径，可用于提高其稳定性和性能，通过加速排水和固结，并提供加固。该创新技术最初由申请人（和合作者）提出，已在加拿大Malartic金矿现场（加拿大QC西部）大规模有效应用超过7年。该技术的成功现场应用还提出了尚未解决（甚至尚未考虑）的其他问题，包括WRI对邻近尾矿饱和度的影响，它们对氧气进入和硫化物矿物产生酸性矿山排水（AMD）的影响，以及这些可能如何影响现场关闭后的复垦工作。这些问题将通过拟议的发现补助金计划（项目A）进行调查。在暴露于自然条件下的堆堆中处置反应性废石是采矿作业的另一个关键问题，因为这些废石可能成为受污染沃茨的主要来源。初步的实验室和现场工作表明，通过在桩顶和桩内增加流动控制层（FCL）来限制表面渗透，可以控制桩内污染渗流沃茨的产生。这些层在桩施工期间放置在每个台阶（和升降机）的表面上，以限制渗透和向桩的反应芯的深层渗透。物理模型、数值模拟和最近在TiO矿（RTFT，Eastern QC）建造的大型实验废石堆的实验室试验表明，该技术具有很大的潜力。但这些研究也揭示了需要更仔细研究的其他关键方面，包括三维效应，FCL下方粗粒废石中的局部水流，以及如何定义最佳条件以最大限度地提高FCL的效率。这些方面也将通过拟议的发现补助金研究计划（项目B）进行调查。

The complex challenges raised for the safe management of large quantities of reactive mine wastes require innovative approaches to address various geo-environmental concerns and ensure the geotechnical and hydrogeochemical stability of the disposal sites. Recent work has shown that waste rock inclusions (WRI) placed along selected paths within tailings impoundment can be used to improve their stability and performance by accelerating drainage and consolidation and providing reinforcement. This innovative technique, initially proposed by the Applicant (and collaborators), has been applied efficiently on a large scale at the Canadian Malartic gold mine site (western QC, Canada) for over 7 years. The successful field application of this technique has also raised additional questions that have not yet been addressed (or even considered), including the effect of WRI on the degree of saturation of adjacent tailings, their influence on oxygen ingress and generation of acid mine drainage (AMD) from sulphide minerals, and  how these may impact the reclamation work upon site closure. These issues will be investigated through the proposed Discovery Grant program (Project A). The disposal of reactive waste rock in piles exposed to natural conditions is another critical issue for mining operations, as these may become a major source of contaminated waters. Preliminary laboratory and field work has shown that it is possible to control the generation of contaminated seepage waters in piles by limiting surface infiltration with the addition of flow control layers (FCL) on the top and inside the pile. These layers are placed during pile construction on the surface of each bench (and lift) to limit infiltration and deep percolation toward the reactive core of the pile. Laboratory tests on physical models, numerical simulations and a recently built large scale experimental waste rock pile at the Tio mine (RTFT, Eastern QC) have shown that this technique has a great potential. But the studies also revealed other key aspects that need to be looked at more closely, including three-dimensional effects, localized water flow in the coarse-grained waste rock below the FCL, and ways to define optimum conditions to maximize the efficiency of FCL in terms of material properties and layer thickness, inclination, and vertical position in the pile. These aspects will also be investigated  through the proposed Discovery Grant research program (Project B).