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

回填采矿产生的大量地下空洞是提供地面支持和区域稳定的一项基本技术，从而促进附近地区的采矿。本研究调查了两种类型的回填：1)胶结过去回填(CPB)，即过滤后的尾矿、粘结剂和水的混合物；2)胶结浆体骨料充填(CPAF)，即含有粉碎废石的尾矿膏。加入足够数量的粘结剂以加强CPB混合物，同时添加水以促进通过管道和钻孔的输送，并防止堵塞形成。为了避免使用大量的水，这会对强度产生负面影响，可以使用目前混凝土中使用的高效减水剂(SP)。SPS允许获得低水分含量(或高固体含量)的可流动和易泵送的多氯联苯，从而减少粘结剂含量并缩短达到所需强度的时间。最有效的聚羧酸盐SP价格昂贵。因此，这项研究的第一个目标是调查更实惠的分散剂的使用，并开发有效和令人信服的工具，以促进在不同气候条件下在矿山充填作业中定期使用这些分散剂。与传统的CPBS相比，当需要更好的机械性能时，CPAF是另一种很有前途的回填技术。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，或者防止产生异质CPAFs的聚集体沉淀所需满足的条件。因此，第二个研究目标是开发设计工具，用于非分离CPAF的最佳配方配方和管道运输。对多年冻土中挖掘的空隙进行回填带来了额外的设计挑战：由于与多年冻土的热交换，CPB在温度下降的情况下变硬，需要先进的数值设计工具来解决这一问题。因此，第三个研究目标是开发用于填充在永久冻土中挖掘的空隙的可靠设计工具。CPB和CPAF混合料的配料一般基于对大量混合料的广泛实验室测试。到目前为止，还没有开发出标准的混合程序来说明不同实验室使用的不同混合时间、混合器负载质量、混合速度和混合器类型。因此，还将研究混合能量和其他几个因素对CPB和CPAF性能的影响。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师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.