Uncemented paste backfill for underground mining

点击翻译按钮获取中文摘要

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.