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Abstract：
The mechanical properties and microstructure of the cemented paste backfill (CPB) in dry-wet cycle environments are particularly critical in backfill mining. In this study, coal gangue, fly ash, cement, glass fiber, and nano-SiO2 were used to prepare CPB, and dry-wet cycle tests on CPB specimens with different curing ages were conducted. The compressive, tensile, and shear strength of CPB specimens with different curing ages under different dry-wet cycles were analyzed, and the microstructural damage of the specimens was observed by scanning electron microscopy (SEM). The results show that compared with the specimens without dry-wet cycles, the uniaxial compressive strength, tensile strength, and shear strength of the specimens with a curing age of 7 d after seven dry-wet cycles were the smallest, being reduced by 40.22%, 58.25%, and 66.8%, respectively. After seven dry-wet cycles, the compressive, tensile, and shear strength of the specimens with the curing age of 28 d decreased slightly. The SEM results show that with the increasing number of dry-wet cycles, the internal structure of the specimen becomes more and more loose and fragile, and the damage degree of the structural skeleton gradually increases, leading to the poor mechanical properties of CPB specimens. The number of cracks and pores on the specimen surface is relatively limited after a curing age of 28 d, while the occurrence of internal structural damage within the specimen remains insignificant. Therefore, the dry-wet cycle has an important influence on the both mechanical properties and microstructure of CPB. This study provides a reference for the treatment of coal-based solid waste and facilitates the understanding of the mechanical properties of backfill materials under dry-wet cycling conditions.
摘要：
干湿循环环境下胶结膏体回填（CPB）的力学性能和微观结构在回填开采中尤为关键。在这项研究中,煤矸石,粉煤灰,水泥,玻璃纤维,和纳米SiO2用于制备CPB，并对不同养护龄期的CPB试样进行了干湿循环试验。压缩，拉伸,分析了不同养护龄期CPB试件在不同干湿循环条件下的剪切强度,并通过扫描电子显微镜（SEM）观察了样品的微观结构损伤。结果表明,与没有干湿循环的试样相比,单轴抗压强度，抗拉强度,七个干湿循环后，固化年龄为7d的试样的剪切强度最小，减少40.22%，58.25%,和66.8%，分别。经过七个干湿循环，压缩，拉伸,28d养护龄期试样的剪切强度略有下降。SEM结果表明,随着干湿循环次数的增加,试样的内部结构变得越来越松散和脆弱，结构骨架的损伤程度逐渐增加，导致CPB试样力学性能较差。在28d的固化时间后，试样表面的裂纹和孔隙数量相对有限，而试样内部的结构损伤的发生仍然是微不足道的。因此,干湿循环对CPB的力学性能和显微组织都有重要影响。该研究为煤基固体废弃物的处理提供了参考，有利于理解干湿循环条件下回填材料的力学性能。
