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，覆盖系统的设计像天然山坡一样，将废物从大气和生物圈中隔离出来，从而保护环境资源和公众健康。目前的覆盖物设计方法包括对废物和覆盖物材料的物理和水力性质(在核心和柱子尺度上)进行实验室测试，然后进行基于计算机的2D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，因为它们改变了盖子的表面渗透和横向分流特性。人们对这种影响知之甚少，很少考虑到用于盖子设计和环境性能测试的预测模型。在这里，我们使用萨斯喀彻温省大学新建的地雷覆盖土壤测试设施(MOST)来探索一系列应用问题，重点是对冻结融化对地雷覆盖物储存和释放的影响的新理解。这些问题是M.A.O‘Kane咨询公司的商业模式的基础，该公司是我们的行业合作伙伴，负责管理和告知客户的不可预见的债务和矿山关闭问题。MOST设施提供了一个独特的环境来检查我们的90平方米室内高湾设施内的山坡尺度过程(这种尺度在受控环境下是不可能的)，其中有15-20平方米的山坡。除了测试山坡规模的冻融对水储存和释放的影响外，我们还将测试新的设计方法，即“季节性冻结的毛细分流”(一种利用地下冻层帮助融化水转移的方法)，作为一种主动解决方案，为北方覆盖系统增加新的功能。

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.