Developing Innovative Shotcrete as Rock Support for Underground Mining in Canada's North

喷射混凝土是指一种水泥基混合物，以气动方式高速投射到目标基材上。喷射混凝土在地下矿山中被广泛用作岩石支撑；然而，多年冻土对设计和使用喷射混凝土来支撑新开挖的冻岩/多年冻土构成了巨大的挑战，因为在冻结的基质上喷射混凝土混合物水化缓慢，导致岩石支撑系统不够硬化和失灵。这是不安全的，因为不充分的硬化可能会导致落石和随后的矿工受伤甚至死亡。对于北方应用，必须加快喷射混凝土的水化，以确保岩石支撑的足够强度；然而，喷射混凝土水化产生的过高热量和矿井内的温暖通风空气会导致周围的永久冻土融化。融化是一个严重的问题，因为它会触发温室气体排放(即甲烷)，威胁全球气候，并破坏地面的稳定，使地下作业不安全。随着加拿大和国外在较冷环境中采矿的增加，在永久冻土中挖掘的地下矿山将需要创新的喷射混凝土和岩石支撑系统。然而，在这一研究领域开展的工作非常有限。在接下来的五年里，我建议开发一种创新的喷射混凝土系统，可以用作加拿大北部和其他永久冻土地区地下采矿的岩石支撑。此外，还将对喷射混凝土和喷射混凝土-多年冻土热相互作用中的热传递过程进行基础研究。拟议研究计划的长期目标是建立一个框架，其中包括加拿大北部地下支撑系统设计的指导方针和软件。加拿大北部的矿业在北部地区和社区的经济和社会增长中发挥着不可或缺的作用；矿业占加拿大北部GDP的20%以上；它也是加拿大原住民最大的私营部门雇主。拟议的研究计划直接有助于开发、表征和了解用于加拿大北部地下岩石支撑的创新喷射混凝土。它还将为进一步研究加拿大北部和其他永久冻土区地下岩石支撑系统设计的基础理论和框架铺平道路。最后，这项研究计划将培训8名高素质的北方采矿工程师，他们可以将他们的知识和学术能力应用于加拿大北部的矿产资源开发。

Shotcrete refers to a cement-based mixture projected pneumatically at high velocity towards the target substrate. Shotcrete has been widely used in underground mines as rock support; however, permafrost poses significant challenges to the design and use of shotcrete to support freshly excavated frozen rock/permafrost because the slow hydration of shotcrete mixture on frozen substrates leads to insufficient hardening and malfunctioning of the rock support system. This is unsafe as insufficient hardening may result in rockfalls and subsequent injuries or even fatalities of mine workers. For northern applications, the hydration of shotcrete must be accelerated to ensure adequate strength for rock support; however, excessive heat produced by shotcrete hydration and warm ventilation air within the mine causes thawing of the surrounding permafrost. Thawing is a serious problem because it triggers greenhouse gas emissions (i.e., methane) threatening global climate and it destabilizes the ground making underground operations unsafe. As mining in colder environments increases in Canada and abroad, innovative shotcrete and rock support systems will be needed for subsurface mine workings excavated in permafrost. However, very limited work has been conducted in this research area. In the next five years, I propose to develop an innovative shotcrete system that can be used as rock support for underground mining in Canada's North and other permafrost regions. Moreover, fundamental research will be conducted on the heat transfer process in shotcrete and shotcrete-permafrost thermal interactions. The long-term goal of the proposed research program is to establish a framework that includes guidelines and software for the design of underground support systems in Canada's North.Mining in Canada's North plays an indispensable role in the economic and social growth of northern regions and communities; mining accounts for over 20% of the GDP of Canada's North; it is also the largest private sector employer of aboriginal Canadians. The proposed research program directly contributes to the development, characterization, and understanding of innovative shotcrete for the use as underground rock support in Canada's North. It will also pave the way for further investigations on the fundamental theory and a framework for underground rock support system design in Canada's North and other permafrost regions. Finally, this research program will train eight highly qualified Northern mining engineers who can apply their knowledge and academic abilities to mineral resource development in Canada's North.