冲击载荷下掺纤维尾砂充填体宏细观力学行为与损破机理实验研究

The stability of cemented tailings backfill (CTB) is crucial for the safe and efficient recovery of pillars in open stoping with subsequent filling method. The two-wing CTBs disturbed by blasting are prone to catastrophic collapse and lumping during the process of pillars mining, a fiber-reinforced cemented tailings backfill (FRCTB) with high overall strength, crack resistance, and impact resistance properties was explored to reduce the dilution caused by tailings mixing. It also can meet the strength requirements of CTB for pillar mining. In view of the lack of research on the mechanical properties of CTB under dynamic loading, the field engineering research, theoretical analysis, laboratory experiments, numerical simulation and on-site industrial application methods are used to investigate the macroscopic and mesoscale mechanical properties and damage evolution mechanism of FRCTB under impact loading. The purpose of this study was to reveal the mechanism of the effect of fibers on the mechanical properties of CTB; to establish a damage constitutive model of FRCTB under different impact loadings; to reveal the mechanism of damage and failure evolution of FRCTB under impact loading. The research not only enriches the research system of dynamic mechanics of CTB, but also provides basic research data for the control of CTB after filling. At the same time, it has important theoretical value and engineering significance for achieving the safe and high-efficiency mining of the pillars, and has a broad prospect for promotion.

胶结充填体稳定性对于实现空场嗣后充填法矿柱安全高效回采至关重要。矿柱回采过程中，两翼充填体受爆破扰动后极易发生垮冒、片帮现象，探索制备一种整体强度高、抗裂和抗冲击性能好的掺纤维尾砂胶结充填体，既能降低尾砂混入造成贫化，又能满足二步矿柱回采强度需求。针对动载荷作用下胶结充填体力学特性研究不足的问题，本课题拟采用现场工程调研、理论分析、室内实验、数值模拟和现场工业应用相结合的研究方法，围绕冲击载荷下掺纤维胶结充填体的力学行为宏观和细观双尺度表征和损破演化机理试验及相关理论开展基础研究。旨在揭示纤维对尾砂胶结充填体力学性能的影响机制；建立不同冲击载荷下掺纤维尾砂充填体的损伤本构模型；揭示冲击载荷下掺纤维尾砂充填体损伤破坏演化机理，为空场嗣后充填法矿柱回采的顺利推广和充填体稳定性控制提供基础研究依据，同时能从理论角度丰富充填体动力学研究体系，具有重要的理论价值和工程意义，推广前景广泛。

本课题采用室内实验、理论分析、数值模拟和现场工业试验相结合的研究方法，开展了纤维类型及掺量对尾砂胶结充填体力学性能影响机制的基础研究，探明了抗弯条件下掺纤维尾砂充填体裂纹扩展机理与演化规律，分析了冲击荷载下掺纤维尾砂充填体的动态力学特性。.（1）从宏观角度研究了掺纤维尾砂充填体的抗压力学特性。结果表明掺纤维充填体具有“裂而不碎”的特征，聚丙烯纤维的增强效果最显著，纤维掺量的临界点为0.6%；充填体Φ50mm的最优纤维长度为12mm，其声发射演变过程可划分为压密、平静、密集和活跃共四个阶段。.（2）探究了掺加纤维对胶结充填体抗裂性能和峰后韧性的改善效果，并建立了数值模型从细观角度揭示了掺纤维充填体梁的裂纹扩展机理和演化规律。发现掺纤维充填体的起裂点位于峰值荷载前，其峰后延性主要受纤维掺量、纤维类型的影响作用；断裂面形貌与纤维性能、分布数量密切相关。.（3）从微观角度揭示了纤维增强作用机理，即纤维直径、表面形态、与胶结充填体基体之间的界面黏结力，是影响纤维脱粘和掺纤维充填体峰后破坏特征的重要因素。其次，结合工业CT和三维重构技术，定量表征了压缩前后掺纤维充填体的内部结构变化特征，得知胶结充填体压缩前的孔隙度随着纤维掺量的增加而增大，其微孔隙结构影响了宏观力学行为的显现；掺加纤维降低了充填体压缩后的损伤值，且K2值与峰值强度呈现正相关。.（4）开展了掺纤维充填体的冲击动力学实验，分析其冲击波形曲线和破坏模式与普通充填体的区别（掺纤维充填体中低应变率冲击下具有二次承载能力），并建立了适用于在冲击荷载作用下掺纤维充填体的本构模型，揭示了冲击荷载下掺纤维充填体的损伤破坏规律，从理论角度丰富了胶结充填体动力学研究体系。最后，以软破矿体下向进路充填法开采中充填假顶构筑工艺为背景，探究了掺纤维充填体工业应用的可行性。