中心孔径对岩石动态断裂韧度测试值的影响

为了考察圆盘试件不同中心孔径对岩石动态断裂韧度测试值的影响,采用直径80 mm含有不同中心圆孔孔径的圆孔裂缝平台巴西圆盘试件,在Hopkinson压杆系统上进行径向冲击试验,获得岩石的动态断裂韧度。结果表明,当中心圆孔孔径与圆盘直径之比r0/R∈(0.10,0.30)时,岩石动态断裂韧度的平均值为4.57 MPa·m1/2,测试值受中心圆孔孔径变化的影响并不明显。试件的断裂模式有一定差异,当圆孔孔径较小时,在主裂纹扩展的过程中萌生较多的次生裂纹;随着孔径的增大,次生裂纹减少,试件呈现更加明显的宏观拉贯通破坏。对于推广中心圆孔裂缝平台巴西圆盘测试岩石动态断裂韧度的方法,以及掌握岩石受到动态冲击时的破坏特性具有重要的意义。

INFLUENCE OF CENTER HOLE DIAMETER ON TEST VALUES OF ROCK DYNAMIC FRACTURE TOUGHNESS

In order to study the influence on determining rock dynamic fracture toughness accurately with center hole，some 80 mm diameter marble specimens of Holed-cracked flattened Brazilian disc(HCFBD) with different diameter of center hole were performed in the split Hopkinson pressure bar system. The results showed that the average rock dynamic fracture toughness was 4.57 MPa?m1/2 as the dimensionless diameter of center hole r0/R∈(0.10，0.30). There was not obvious change for the test results of dynamic fracture toughness with different diameter of center hole，but there were a certain differences about specimen fracture patterns. When the center hole diameter was small，there were more secondary cracks in the process of the main crack extension. However，there were more obvious macro transfixion fracture and less secondary cracks with the increase of the center hole diameter. Which provides an important significance to promote the method of determining rock dynamic fracture toughness with Holed-cracked flattened Brazilian disc and to reveal the rock fracture characteristics under dynamic impact.