It is not uncommon that backfill material used in underground mining being exposed to repetitive dynamic stresses induced by blasting operations or rockburst events. Understanding the strength and fracture evolution of backfilled stopes is critical to maintain the long-term stope stability and ensure safe mining activities. This paper aims to study the damage evolution of the backfill material and its host rock behaviour under three-dimensional (3D) dynamic loading. Using a true-triaxial testing machine, multiple samples of backfill material enclosed by country rock were fabricated and tested under various dynamic loadings with different true-triaxial confining stress conditions. In addition, the nuclear magnetic resonance (NMR) measurement was conducted on the samples before and after exerting static and dynamic loading to obtain their porosity distribution changes. The experiment results suggested that with the increase of the dynamic loading, the porosity of the backfill sample goes through a two-stage process, which shows a slightly linear decrease and then followed by an exponential increase. The research findings can help understand the damage mechanism and fracture development of backfilled stopes and its host rock in deep underground mines, which are constantly subject to the combination of 3D static confining stress and dynamic loading.

地下采矿中使用的回填材料经常受到爆破操作或岩爆事件引起的重复性动态应力的影响，这种情况并不少见。了解回填采场的强度和断裂演化对于维持采场的长期稳定性和确保安全的开采活动至关重要。本文旨在研究三维（3D）动态载荷下回填材料的损伤演化及其基质岩石的行为。使用真三轴试验机，制造了多个由乡村岩石围起来的回填材料样品，并在具有不同真三轴约束应力条件的各种动态载荷下进行了测试。此外，在施加静态和动态载荷之前和之后对样品进行核磁共振（NMR）测量，以获得其孔隙率分布变化。实验结果表明，随着动态载荷的增加，回填样品的孔隙率经历了一个两阶段的过程，即呈线性下降，然后呈指数增长。研究结果有助于理解深部地下矿山中回填采场及其母岩的破坏机理和裂缝发展，而这些矿山经常受到3D静态约束应力和动态载荷的共同作用。它显示出线性的下降，然后呈指数上升。研究结果有助于理解深部地下矿山中回填采场及其母岩的破坏机理和裂缝发展，而这些矿山经常受到3D静态约束应力和动态载荷的共同作用。它显示出线性的下降，然后呈指数上升。研究结果有助于理解深部地下矿山中回填采场及其母岩的破坏机理和裂缝发展，而这些矿山经常受到3D静态约束应力和动态载荷的共同作用。