岩石动态断裂韧度的尺寸效应

采用两种圆孔裂缝平台巴西圆盘试件(一种为直径分别为42、80、122、155 mm的几何相似试件，另一种为直径80 mm、仅裂缝长度不同的单一尺寸试件)对岩石动态断裂韧度的尺寸效应进行了研究。给出了在霍普金森压杆系统上对试件进行径向撞击产生的应变波形和断裂模式。实验结果表明，对于几何相似试件，动态断裂韧度的测试值随着尺寸的增大而增大，而对于单一尺寸试件，其测试值随着中心裂缝长度的增加呈现先增大后减小的趋势。裂缝前端的断裂过程区长度和孕育时间是岩石动态断裂韧度测试值表现为尺寸效应的主要原因，为了减小尺寸效应，建立了考虑这两个参数在空间-时间域对动态应力强度因子的分布进行积分后再平均来确定岩石动态断裂韧度的方法。

Size effect of rock dynamic fracture toughness

In the experiments, two types of holed-cracked flattened Brazilian disc specimens were adopted, one was geometrically similar with the diameters of 42, 80, 122 mm and 155 mm respectively, the other was a one-size specimen geometry with an identical 80-mm diameter and varying crack lengths. The discs were diametrically impacted by the split Hopkinson pressure bar, and the strain waves and typical failure patterns of the specimens were given. It is concluded that the rock dynamic fracture toughness increases with the increasing diameter size for the geometrically similar specimens; however, it increases and then decreases with the increasing crack lengths for the specimens of the identical 80-mm diameter. The size effect of rock dynamic fracture toughness is caused by the fracture process zone length l and incubation time τ. To reduce the size effect, a method to determine the rock dynamic fracture toughness was proposed by averaging the integration of dynamic stress intensity factor distribution in the spatio-temporal domain.