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

喷射混凝土是指以高速向目标基底喷射的水泥基混合物。喷射混凝土已被广泛用于地下矿山作为岩石支护;然而，永久冻土对喷射混凝土的设计和使用提出了重大挑战，以支持新开挖的冻结岩石/永久冻土，因为喷射混凝土混合物在冻结基质上的缓慢水合导致岩石支护系统硬化不足和故障。这是不安全的，因为不充分的硬化可能会导致岩石坠落，随后造成矿工受伤甚至死亡。对于北方应用，必须加速喷射混凝土的水合作用，以确保岩石支护有足够的强度;然而，喷射混凝土水合作用产生的过多热量和矿井内的热通风空气会导致周围永久冻土融化。解冻是一个严重的问题，因为它会引发温室气体排放（即，甲烷）威胁全球气候，并使地面不稳定，使地下作业不安全。

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.