Characterization of Static Liquefaction in Tailings through the Critical State Framework

尾矿储存设施(TSF)是用于储存采矿废物的人造土结构，由细矿物和开采过程中留下的水组成。它们存在于经济、安全和可持续发展的交汇点。采矿业需要更好的工程实践来评估和改进现有的TSFs，设计新的TSFs和处置流程，其动机是：TSFs最近的灾难性故障；要求降低尾矿处置成本的经济挑战；以及不断变化的监管和社会压力，以提高尾矿储存的安全性和可持续性。粒状土壤，如尾矿，可能会在一个称为液化的过程中失去全部或部分强度。液化是一种现象，当松散致密的颗粒想要形成更致密的结构时，但空隙中的水的存在阻止了这一点，代价是增加了水中的压力。结果是显而易见的：如果水压足够大，整个混合物就会变成“液体”。土壤对液化的抵抗力主要取决于其颗粒的密实程度。液化势的评估是通过估计土壤的密度，根据其对穿透探头的抵抗力。圆锥贯入测试(CPT)是现场表征的主要工具，因为它以快速和廉价的应用提供了丰富的信息。 评估液化对TSF的潜在威胁涉及三个步骤：CPT如何估计尾矿的密度，在考虑到尾矿密度的情况下是否会发生液化，以及如果发生液化，尾矿将保留多大强度。经常在加拿大和世界各地就TSF项目进行合作的顾问(Gold)和专业承包商(ConeTec)与多伦多大学走到了一起，汇集了他们的专业知识，并回答了这些紧迫的问题。 拟议的伙伴关系将产生一个新的针对尾矿的液化评估框架。因此，加拿大顾问、承包商和矿业公司将获得竞争优势，从而增加工作和就业，降低运营成本，最重要的是设计更安全。

Tailings storage facilities (TSF) are man-made earth structures used for storing mining waste, comprised of fine minerals and water left behind during the extraction process. They exist at the intersection of economics, safety, and sustainability. The mining industry needs better engineering practices for assessing and improving existing TSFs, designing new TSFs, and disposal processes motivated by: recent catastrophic failures of TSFs; economic challenges demanding reductions in tailings disposal costs; and evolving regulatory and social pressures to improve the safety and sustainability of tailings storage. Granular soils, such as tailings, can lose all or part of their strength in a process called liquefaction. Liquefaction is the phenomenon that happens when loosely compacted particles "want" to form a denser structure, but presense of water in the voids prevents that, at the cost of increasing pressure in the water. The result is obvious: if the water pressure sufficiently increases, the whole mixture will turn into a "liquid". Soils' resistance to liquefaction mainly depends on how densely-packed its particles are. Liquefaction potential is assessed by estimating soil density from its resistance to a penetrating probe. The Cone Penetration Test (CPT) is the predominant site characterisation tool since it provides a wealth of information with fast and inexpensive application. Assessing the potential threat of liquefaction to a TSF involves three steps: How the CPT estimates the density of tailings, if liquefaction will occur given the density of tailings, and how much strength the tailings will retain should liquefaction occur. A consultant (Golder) and a specialty contractor (ConeTec) who often collaborate on TSF projects in Canada and around the world have come together with University of Toronto to pool their expertise and answer these pressing questions. The proposed partnership will produce a new tailings-specific liquefaction assessment framework. Consequently, Canadian consultants, contractors, and mining companies will obtain a competitive edge leading to added work and employment, reduced cost of operation, and most importantly safer designs.