Alternative materials for engineered covers used to control acid mine drainage

当今采矿业面临的最严重的环境挑战之一是矿山废物处置区的复垦，特别是当它们含有可产生酸性矿山废水（AMD）的硫化物矿物时。拟议的研究计划旨在通过使用替代材料作为覆盖组件来改进覆盖技术，并分为两个不同的项目：1）评估作为覆盖材料的膏岩; 2）评估工程覆盖中的膨润土基细粒材料。 在项目1中，将制备、表征和测试具有不同废石与尾矿比率的膏体岩石。膏状岩石混合物的性能将进行比较，在水文地质特性方面，与理论预测使用混合物理论。大型柱试验的结果，其中膏体岩石被用作覆盖材料，将与现有的现场实验单元的结果进行比较。这两种装置都将安装仪器，以测量不饱和水的运动和气体迁移，并将允许回收沥滤液。从物理模型（柱试验和现场实验单元）获得的结果将与水文地球化学数值模型的结果进行比较。 当矿区附近无法获得传统的细粒材料时，膨润土基细粒材料（土壤-膨润土或土工复合粘土衬垫（GCL））是令人感兴趣的覆盖材料选择。候选人最近的工作表明，岩石-膨润土混合物在短时间内有效控制氧迁移，但受冻融循环的影响很大。在项目2中，将在实验室中对不同土壤膨润土混合物进行详细表征。根据表征结果，将在温控室中进行仪器化柱试验，以评估暴露于冻融循环时基于硅灰石的覆盖物在控制氧和水迁移方面的性能。GCL也将在本项目中作为工程覆盖层中使用的细粒层进行研究。候选人可进入一个矿场，而该矿场使用GCL作为现有覆盖材料。实验室测试（例如，水和空气的渗透性，微观结构特征）的完整，冻融循环后，和原位样品将进行评估的能力，GCL控制流体（水和气体）的运动时，安装在AMD产生的矿场。 拟议的研究计划将提供新的或改进的技术，为AMD产生的矿山废物处置区的复垦。这项工作将由HQP执行，HQP将从培训中受益，成为具有减少采矿对环境影响的知识和能力的高价值专家，同时支持该行业可持续开采金属资源的目标。

One of the most serious environmental challenges facing the mining industry today is the reclamation of mine waste disposal areas, especially when they contain sulphide minerals that can produce acid mine drainage (AMD). The proposed research program seeks to improve cover technologies through the use of alternative materials as cover components, and is divided into two distinct projects: 1) assessment of paste rock as cover material; 2) assessment of bentonite based fine grained materials in engineered covers. In Project 1, paste rocks with different waste rock to tailings ratios will be prepared, characterized, and tested. The performance of the paste rock mixtures will be compared, in terms of hydrogeological properties, with theoretical predictions made using Mixture theory. The results of large-scale column tests, in which paste rocks are used as cover material, will be compared with the results from existing field experimental cells. Both set-ups will be instrumented to measure unsaturated water movement and gas migration, and will allow for leachates to be recovered. Results obtained from the physical models (column tests and field experimental cells) will be compared with those from hydrogeochemical numerical models. Bentonite-based fine-grained materials (soil-bentonite or geocomposite clay liner (GCL) are interesting options as cover materials when traditional fine-grained materials are not available near the mine site. Recent work performed by the candidate demonstrated that rock-bentonite mixtures are efficient in controlling oxygen migration over short periods, but are significantly influenced by freeze-thaw cycles. In Project 2, a detailed characterization of different soil bentonite mixtures will be performed in the lab. Based on the results of the characterizations, instrumented column tests in a temperature-controlled chamber will be performed to assess the performance of bentonite-based covers in controlling oxygen and water migration when exposed to freeze-thaw cycles. GCL will also be investigated in this project as a fine-grained layer used in engineered covers. The candidate has access to a mine site where GCL is used as an existing cover material. Laboratory tests (e.g., water and air permeability, microstructural characterization) on intact, post-freeze-thaw cycles, and in situ samples will be performed to evaluate the capacity of GCL to control fluid (water and gas) movement when installed at AMD-generating mine sites. The proposed research program will provide new or improved techniques for the reclamation of AMD-generating mine waste disposal areas. The work will be performed by HQP, who will benefit from this training by becoming highly-valued specialists with the knowledge and ability to reduce the environmental impacts of mining, while supporting the industry's goal of sustainable exploitation of metal resources.