低温环境下含盐膏体流动与力学特性研究

Cemented paste backfill (CPB) technology has been increasingly used in cold regions. Research evidence from these areas indicates that saline underground water is very widespread and mine water also contains some kinds of salts, which means that the water available for the preparation of CPB in some of these cold regions is often saline. Nevertheless, the presence of salt in the pore fluid significantly affects the engineering properties of CPB. In the light of this, this study aims to investigate the flowability, freezing behavior and mechanical properties of saline CPB in low-temperature environments. First, the combined effect of salt and temperature on the time-dependent rheological properties of fresh CPB is studied. An elastic viscoplastic rheological model and a mathematical formula for calculating the piping resistance are built to describe the flowability of saline CPB exposed to low temperatures. Furthermore, the freezing behavior of saline CPB exposed to the sub-zero environments and the coupled relations between the performance parameters are studied by means of columns experiments. Subsequently a coupled thermo-hydro-mechanical-chemical model for simulating freezing behavior is developed. Finally, this proposed study experimentally investigates the mechanical behavior of saline CPB in low-temperature environments. The mechanisms responsible for the macroscopic behavior will be revealed from microcosmic point of view. On this basis, a mathematical model for predicting strength will be developed. The findings of this study can provide critical references for the proportioning, transportation and structure design of saline CPB in cold regions.

矿山膏体充填开采正逐步向寒冷地区发展。寒区含盐地下水分布非常广泛，同时矿井水也含有不同种类和浓度的盐分，这导致矿山制备的膏体通常含有一定的盐分，而盐分的存在显著影响着膏体的管流行为和力学稳定性。项目以低温环境下含盐膏体为研究对象，围绕料浆流动特性、充填体冻结特性以及力学特性三个关键性能指标，重点研究盐分和温度耦合作用下膏体料浆流变特性及时变规律，构建描述其流动行为的弹粘塑性流变模型和管输阻力计算方程；研究低温环境下含盐膏体的冻结特性，探明THMC多过程参量之间的相互作用关系，建立反映含盐膏体冻结行为的多过程耦合数值模型；分析低温环境下膏体的力学性能演化规律，从微观角度揭示其宏观力学行为的内在作用机制，构建含盐膏体强度预测数学模型。研究成果可以为低温环境下含盐膏体配比、输送、结构优化设计等提供关键理论依据。

矿山膏体充填开采正逐步向寒冷地区发展。寒区含盐地下水分布非常广泛，同时为了避免输送过程中料浆发生冻结，往往加入一些盐来降低凝结点。鉴于此，本项目针对低温下含盐膏体充填材料的流动性和强度进行了深入研究。首先，利用旋转流变仪获得了温度、盐种类和浓度耦合下膏体料浆流变特性及时变规律，得到了相应的管输阻力计算方程；其次，利用土柱试验得到了膏体充填材料在冻结过程中的温度、含水量、孔隙率、电导率演化特征，发现电导率-温度-含水量间存在显著的耦合关系；再次得到了低温环境下含盐膏体的力学性能演化规律，并借助水化产物、水化动力学和冰点测试结果揭示了内在机理；最后，通过一系列的探索实验，发现极少量的钙盐的掺入能够显著提高低温下碱激发矿渣充填体的强度。本项目的研究成果可以为寒区含盐膏体配比、输送、结构优化设计等提供关键理论依据。