Modification of hydro-geotechnical properties of tailings for optimization of high density deposition

贱金属、贵金属、铝和沥青的露天开采都会产生大量的尾矿：水中的细颗粒悬浮物，来源于碾磨过程中对主岩的研磨或挖掘覆盖层中的土壤。在加拿大，仅贱金属和贵金属开采每年通常就产生2亿至5亿立方米的尾矿，是城市固体废物产生率的20倍以上，而且随着加拿大北部不断扩大的矿山开发开放，这种尾矿还可能增加。这些设施的典型占地面积约为几平方公里，水坝高度超过200米。油砂尾矿池是从太空中可见的少数人造结构之一。与尾矿相关的主要影响是不可回收的和/或污染的水流失到尾矿-水基质中，灾难性故障的风险（最近发生在2010年10月4日匈牙利的红泥尾矿灾难）以及随之而来的环境和经济破坏，以及难以对浆状尾矿进行脱水以产生复垦所需的强度。 为了减少这些影响，各种采矿业一直在研究一系列技术，以更高的密度开采和存款尾矿。 这些技术在不同程度上依赖于自然脱水过程，例如沉降和干燥（通过蒸发、排水或冻融），以最大限度地提高密度和强度。控制沉积后密度增加的性质基本上都基于微观结构，即单个颗粒的尺寸分布和排列。工程师们有能力通过改变孔隙水的化学性质以及去除或添加某些颗粒来改变微观结构。这项研究调查了这些修改如何影响尾矿的微观结构，从而影响它们通过自然过程获得的密度和强度。这将提高高密度尾矿沉积技术的可行性、成本和环境可持续性。

Base metal, precious metal, aluminum, and surface mining of bitumen all generate substantial volumes of tailings: fine particulate suspensions in water originating from either the grinding of host rock during milling or from soil in excavated overburden. Base and precious metal mining alone typically generates 200-500 million cubic metres per year of tailings in Canada, over 20 times the generation of rate of municipal solid waste, and likely to increase with growing mine development opening up in Canada's North. Typical footprints of these facilities are in the order of several square kilometres, with dams in excess of 200 m high. Oil sands tailings ponds are some of the few manmade structures visible from space. Major impacts associated with tailings are irrecoverable and / or polluted water lost to the tailings-water matrix, the risk of catastrophic failure (occurring as recently as the red mud tailings disaster in Hungary on Oct. 4th 2010) and consequent environmental and economic devastation, and the difficulty in dewatering slurry tailings to generate the strength necessary for reclamation. To reduce these impacts, the various mining industries have been investigating a range of techniques to dewater and deposit tailings at a higher density. These techniques rely to different extents on natural dewatering processes, such as settling and desiccation (by evaporation, drainage, or freeze-thaw), to maximize density and strength. The properties governing the increase in density post-deposition are all fundamentally based on the microstructure, that is the size distribution and arrangement of individual particles. Engineers have some capacity to alter the microstructure by modifying pore-water chemistry and by removing or adding certain particles. This study investigates how such modifications affect the microstructure of the tailings, and therefore the density and strength they can gain through natural processes. This will improve the feasibility, cost, and environmental sustainabilty of high density tailings deposition techniques.