Uncemented paste backfill for underground mining

水泥膏体回填（CPB）由细粒尾矿与水和粘合剂混合而成，形成非牛顿、非离析、致密的泥浆，可用于填充采空区（采场），最终硬化并提供区域地面支撑。在过去的四年里，我们的研究小组在三个不同的运营矿山的6个采场进行了广泛的CPB现场测试。重点包括量化快速填充过程中的回填行为，评估保持填充质量的路障的性能;以及监测生产爆破和近场岩石爆破（高达3.8 Nuttli震级）产生的动态载荷的反应。现场工作的结果，结合有代表性的CPB样品的实验室测试，表明许多工程设计显着低估了CPB的抗液化在静态和动态加载条件下。此外，某些采矿方案甚至可能需要使用非胶结膏体回填-目前认为这种方法“风险太大”，根本无法考虑。拟议的研究旨在制定一个框架，用于评估UPB可能适用的地下采矿条件，特别是如果引入低成本外加剂（通常用于民用建筑行业）以增加回填密度和抗液化潜力。四名研究生将花费五年时间研究各种混合设计，以确定其微观结构及其对工程性能的影响，包括流体力学（耦合流体流动和应力应变）行为和动态强度。先进的数值建模工具将用于模拟实验室中使用的缩放物理模型，从而产生一种可以可靠地用于预测全场尺度行为的建模方法。然后将进行范围研究，以确定未来项目在运营矿山中实际测试UPB概念的潜力。如果研究结果得到充分实现，其影响将是更有效的采矿做法，并证明其安全性，从而提高采矿的经济和环境可持续性。

Cemented Paste Backfill (CPB) consists of fine-grained mine tailings mixed with water and binder to create a non-Newtonian, non-segregating, dense slurry that can be used to fill mined-out openings (stopes) where it will eventually harden and provide regional ground support. Over the last four years our research group has carried out extensive field instrumentation of CPB in 6 stopes in three different operating mines. Highlights have included quantifying backfill behaviour during rapid filling and assessing the performance of barricades that retain the fill mass; and monitoring paste response to dynamic loads arising from production blasting and near-field rock bursting (up to 3.8 Nuttli magnitude). The results of the fieldwork, combined with laboratory testing on representative CPB samples, suggest that many engineering designs are significantly underestimating CPB's resistance to liquefaction under both static and dynamic loading conditions. Furthermore, certain mining scenarios may even warrant the use of Uncemented Paste Backfill (UPB) - an approach currently considered "too risky" to be contemplated at all. The proposed research intends to develop a framework for assessing the underground mining conditions for which UPB may be possible, especially if low-cost admixtures (commonly used in the civil construction industry) are introduced to increase backfill density and resistance to liquefaction potential. Four graduate students will spend five years studying various mix designs to determine their microstructure and resulting impact on engineering properties, including hydromechanical (coupled fluid-flow and stress-strain) behaviour, and dynamic strength. Sophisticated numerical modeling tools will be used to simulate scaled physical models used in the laboratory, resulting in a modeling approach that can reliably be used to predict full field scale behaviour. A scoping study will then be carried out to determine the potential for a future project to actually test the UPB concept in an operating mine. If research results are fully realized, the impact will be more efficient mining practices with a demonstrated level of safety, resulting in better economic and environmental mining sustainability.