Quantifying the effects of freeze-thaw cycles on mine cover system design and performance

土壤覆盖系统用于将活性矿山废物与环境隔离，并限制水和氧气进入下面的尾矿和废石。通常，覆盖系统的设计功能类似于天然山坡，并将废物与大气和生物圈隔离开来，从而保护环境资源和公众健康。目前的盖设计方法包括对废物和盖材料的物理和水力特性进行实验室测试（在核心和柱级），然后进行基于计算机的二维有限元建模。但在加拿大和其他寒冷地区，冻融循环使设计过程复杂化，因为它们改变了覆盖层的表面渗透和侧向导流特性。人们对这种影响了解甚少，而且很少将其包括在用于盖子设计和环境性能测试的预测模型中。本文利用萨斯喀彻温大学新建的矿山覆盖层土壤测试设备（MOST），探讨了一系列应用问题，重点是对冻融效应对矿山覆盖层储存和释放的新认识。这些问题是我们的行业合作伙伴M.A. O'Kane Consultants Inc.的商业模式的基础，用于管理和通知客户不可预见的责任和他们的矿山关闭问题。MOST设施提供了一个独特的环境，可以在我们90平方米的室内高湾设施内，在15-20平方米的山坡上检查山坡尺度的过程（以前在受控环境中不可能实现的规模）。除了测试山坡尺度的冻融对水储存和释放的影响外，我们还将测试“季节性冻结毛细血管断裂分流”的新设计方法（一种使用地下冻结层来帮助融水分流的方法），作为为北方覆盖系统添加新功能的主动解决方案。

Soil cover systems are used to isolate reactive mine wastes from the environment and limit water and oxygen ingress into the tailings and waste rock below. Typically, cover systems are designed to function like natural hillslopes and to isolate waste material from the atmosphere and biosphere, thereby protecting environmental resources and public health. The current approach to cover design includes laboratory testing of the physical and hydraulic properties of waste and cover materials (at the core- and column-scale), followed by computer-based 2D finite element modeling. But in Canada and other cold regions, freeze thaw cycles complicate the design process because they change the surface infiltration and lateral diversion properties of the cover. Such effects are very poorly understood and rarely include in predictive models used for cover design and environmental performance testing. Here we use the newly constructed Mine Overlay Soil Testing facility (MOST) at the University of Saskatchewan to explore a set of applied questions focused on new understanding of freeze thaw effects on mine cover storage and release. These questions are fundamental to the business model of M.A. O'Kane Consultants Inc., our industry partner, for managing and informing unforeseen liabilities with their customers and their mine closure problems. The MOST facility provides a unique setting to examine hillslope-scale processes (a scale not before possible in a controlled setting) within our 90 m2 indoor high bay facility with 15-20 m2 hillslopes. Beyond testing hillslope-scale freeze-thaw effects on water storage and release, we will test new design approaches for 'seasonally frozen capillary break diversion' (a way of using subsurface frozen layers to aid in melt water diversion) as a proactive solution to add new functionality to Northern cover systems.