不同偏置裂纹充填体断裂特性试验

为了研究含缺陷胶结充填体的断裂特性，分别设置了裂纹偏置比为0、0.25、0.50、0.75，缝高比为0.10、0.25、0.50的胶结充填体试件进行三点弯曲试验，利用高速摄像机进行裂纹扩展模式全程捕捉，借助二维颗粒流软件PFC2D对充填体裂纹扩展全程、破断方式及断裂机制进行分析。试验结果表明：相同缝高比下，随着裂纹偏置比的增加，断裂峰值荷载越大；当偏置比一定时，随着缝高比的增加，断裂峰值荷载越小；裂纹偏置比在0、0.25和0.50时，裂纹从偏置处扩展，且随着偏置比的增加，偏折角增大；裂纹偏置比在0.75时，裂纹从中心处扩展；断裂裂纹可分为3个阶段，且呈锯齿状扩展并在发育的过程中不断有碎裂状颗粒产生和脱落。利用二维颗粒流模拟充填体试件的力链网络、速度场及破断方式，结合其宏观力学的试验结果进行对比分析，探讨了细观断裂机制，其断裂时的峰值荷载与试验值相差不超过3.8%。

An experiment on fracture characteristic behaviour of cemented backfill with different offset notch cracks

To study the fracture characteristic behaviour of the defective cemented backfill, three-point bending tests were carried out on the cemented backfill specimens with the offset ratios of 0, 0.25, 0.50, 0.75 and with the seam height ratios of 0.10, 0.25, 0.50, respectively. A high-speed camera was employed to capture the full-range crack propagation, and two-dimensional particle flow software PFC2D was used to analyse the crack propagation process, the fracture mode and the fracture mechanism of the cemented backfill. The results showed that the fracture peak load increased with the increase of the crack offset ratio at the same seam height ratio. When the offset ratio was constant, the peak load was smaller with the increase of the seam height ratio. When the crack offset ratio was at 0, 0.25 and 0.50, the crack propagated from the offset, and the deflection angle increased with the increase of the offset ratio. When the crack offset ratio was at 0.75, the crack propagated from the centre. The crack propagation process was divided into three stages, and it was serrated-shaped. The fragmented particles were generated and shed during the crack propagation process. Two-dimensional particle flow model was employed to simulate the force chain network, velocity field and fracture mode of specimens. The obtained results were compared with experimental results of macro mechanics to explore the mesoscopic fracture mechanism. The peak loading of the fracture was not more than 3.8% compared with the experimental value.