Improving the rheological, mechanical, thermal, and geoenvironmental behavior of cemented backfills to derive the benefits

回填由矿山矿石移除产生的大型地下空洞是提供地面支撑和区域稳定性的必要技术，从而促进附近区域的矿石移除。本研究调查了两种类型的回填：1）胶结过去回填（CPB），过滤尾矿，粘合剂和水的混合物;和2）胶结膏体骨料填充（CPAF），或尾矿膏体纳入粉碎废石。 加入足量的粘合剂以增强CPB混合物，同时加入水以促进通过管道和钻孔的输送流并防止形成堵塞。为了避免使用对强度产生负面影响的大量水，可以使用目前用于混凝土中的超增塑剂（SP）。SP允许获得具有低水含量（或高固体含量）的可流动且易于泵送的CPB，从而减少粘合剂含量并缩短达到所需强度的时间。最有效的聚羧酸盐SP是昂贵的。因此，本研究的第一个目标是调查使用更负担得起的分散剂，并开发有效和令人信服的工具，以促进其在不同气候条件下的矿山回填作业中的定期使用。 与传统的CPB相比，当需要上级机械性能时，CPAF是另一种有前途的回填技术。到目前为止，很少有研究涉及这些材料的流动性，它们在管道运输过程中的行为，或为防止产生异质CPAF的聚集体沉降而应满足的条件。因此，第二个研究目标是开发设计工具，用于非隔离CPAF的最佳配方配方和管道运输。 在永久冻土中挖掘的空隙中进行回填会带来额外的设计挑战：由于与永久冻土进行热交换，CPB会在温度降低的情况下硬化，需要先进的数值设计工具来解决这个问题。因此，第三个研究目标是开发强大的设计工具，在冻土中挖掘的孔隙。 CPB和CPAF混合料配比通常基于大量混合料的广泛实验室测试。迄今为止，还没有开发出标准化的混合程序来解释不同实验室使用的混合时间、混合器负载质量、混合速度和混合器类型。因此，混合能量和其他几个因素对CPB和CPAF性能的影响也将被研究。 将发展先进和创新的科学知识，以获得最大的技术、经济和环境效益。新开发的工具将分发给潜在用户，包括科学界、采矿业和工程咨询公司的回填工程师、分散剂行业新助剂的设计者以及各部委和政府机构。

Backfilling of large underground voids created by mine ore removal is an essential technology to provide ground support and regional stability, thereby facilitating ore removal from nearby regions. This study investigates two types of backfill: 1) cemented past backfill (CPB), a mixture of filtered tailings, binder, and water; and 2) cemented paste aggregate fill (CPAF), or tailings paste incorporating crushed waste rocks. Binder is added in sufficient quantity to strengthen CPB mixtures, and water is simultaneously added to facilitate transport flow through pipelines and drill holes and to prevent plugs from forming. To avoid using large quantities of water, which negatively impact strength, superplasticizers (SP) currently used in concretes can be used. SPs allow obtaining flowable and easily pumpable CPBs with low water content (or high solids content), thereby reducing the binder content and shortening the time to achieve the required strength. The most effective polycarboxylate SPs are expensive. Hence, the first objective of this study is to investigate the use of more affordable dispersants and to develop effective and convincing tools to promote their regular use in mine backfill operations under different climatic conditions. CPAF is another promising backfill technology when superior mechanical properties are required compared to classical CPBs. Few studies to date have addressed the flowability of these materials, their behavior during pipeline transport, or the conditions to be met to prevent sedimentation of aggregates, which produces heterogonous CPAFs. The second study objective is therefore to develop design tools for optimal recipe formulation and pipeline transport of non-segregating CPAF. Backfilling in voids excavated in the permafrost raises additional design challenges: CPB hardens under decreasing temperature due to heat exchange with the permafrost, and advanced numerical design tools are needed to address this issue. The third study objective is therefore to develop robust design tools for backfilling voids excavated in the permafrost. CPB and CPAF mix proportioning is generally based on extensive laboratory testing of a large number of mixes. To date, no standardized mixing procedure has been developed to account for the variable mixing times, mixer load mass, mixing speeds, and types of mixers used at different laboratories. Hence, the influence of the mixing energy and several other factors on CPB and CPAF properties will also be investigated. Advanced and innovative scientific knowledge will be developed in order to derive the maximum of technological, economic, and environmental benefits. The newly developed tools will be disseminated to potential users, including the scientific community, backfill engineers in the mining industry and at engineering consulting firms, designers of new adjuvants in the dispersants industry, and ministries and governmental agencies.