Chemical composition of slag.

Polypropylene fiber was equally mixed into alkali-activated slag fly ash geopolymer in order to ensure the filling effect of mine goaf and improve the stability of cemented gangue paste filling material with ecological matrix. Triaxial compression tests were then conducted under various conditions. The mechanical properties and damage characteristics of composite paste filling materials are studied, and the damage evolution model of paste filling materials under triaxial compression is established, based on the deviatoric stress-strain curve generated by the progressive failure behavior of samples. Internal physical and chemical mechanisms of the evolution of structure and characteristics are elucidated and comprehended via the use of SEM-EDS and XRD micro-techniques. The results show that the fiber can effectively improve the ultimate strength and the corresponding effective stress strength index of the sample within the scope of the experimental study. The best strengthening effect is achieved when the amount of NaOH is 3% of the mass of the solid material, the amount of fiber is 5‰ of the mass of the solid material, and the length of the fiber is about 12 mm. The action mode of the fiber in the sample is mainly divided into single-grip anchoring and three-dimensional mesh traction. As the crack initiates and develops, connection occurs in the matrix, where the fiber has an obvious interference and retardation effect on the crack propagation, thereby transforming the brittle failure into a ductile failure and consequently improving the fracture properties of the ecological cementitious coal gangue matrix. The theoretical damage evolution model of a segmented filling body is constructed by taking the initial compaction stage end point as the critical point, and the curve of the damage evolution model of the specimen under different conditions is obtained. The theoretical model is verified by the results from the triaxial compression test. We concluded that the experimental curve is in good agreement with the theoretical curve. Therefore, the established theoretical model has a certain reference value for the analysis and evaluation of the mechanical properties of paste filling materials. The research results can improve the utilization rate of solid waste resources.

为保障矿山采空区充填效果、提升生态基体胶结煤矸石膏体充填材料的稳定性，将聚丙烯纤维均匀掺入碱激发矿渣粉煤灰基地聚合物中。随后在多种工况下开展三轴压缩试验，针对复合膏体充填材料的力学性能与损伤特性展开研究，并基于试样渐进破坏行为生成的偏应力-应变曲线，建立了三轴压缩工况下膏体充填材料的损伤演化模型。借助扫描电子显微镜-能谱仪（SEM-EDS）与X射线衍射（XRD）微观表征技术，阐明并解析了材料结构与特性演化的内在物理化学机制。试验结果表明：在本研究的试验范围内，聚丙烯纤维可有效提升试样的极限强度与对应有效应力强度指标；当氢氧化钠（NaOH）掺量为固体物料质量的3%、纤维掺量为固体物料质量的5‰、纤维长度约12mm时，材料的强化效果最优。纤维在试样中的作用模式主要分为单端锚固与三维网格拉结两种：当裂纹萌生并扩展时，纤维会在基体中形成拉结作用，对裂纹扩展产生显著的抑制与延缓效应，将原本的脆性破坏转变为延性破坏，进而改善生态胶结煤矸石基体的断裂性能。本研究以初始压密阶段终点作为临界点，构建了分段式充填体的理论损伤演化模型，并得到不同工况下试样损伤演化模型的曲线；通过三轴压缩试验结果对该理论模型进行验证，结果表明试验曲线与理论曲线拟合度良好。综上，所建立的理论模型可为膏体充填材料的力学性能分析与评价提供一定参考价值；本研究成果可提升固体废弃物资源的综合利用率。