不同倾角裂隙混凝土试件动态力学破坏特性试验研究

Experimental study on dynamic mechanical failure characteristicsof concrete specimens with cracks of different angles

为了探讨含不同倾角裂隙的混凝土试件在冲击荷载作用下的力学特性及破坏规律,采用分离式霍普金森压杆(split Hopkinson pressure bar, SHPB)对含有5种不同倾角裂隙的混凝土试件进行了冲击试验,借助高速摄像系统实时捕捉了裂纹扩展和动态破坏过程。结果表明:倾角为30°的裂隙试件的反射波波幅相对最大,倾角为0°的裂隙试件的反射波波幅相对较小。当预制裂隙倾角为0°时,冲击波耗散较少,透射波波幅较大;当预制裂隙倾角为60°时,冲击波耗散较多,即当应力波传播方向与预制裂隙夹角为60°时试件最容易发生破坏。冲击荷载下新形成的裂纹整体上均沿着预制裂隙尖端起裂、扩展和贯通,破坏模式主要为压应力作用下的张拉破坏;在相同预制裂隙宽度下,长度为20 mm预制裂隙的破坏形式比10 mm长度预制裂隙试件更加简单,形成新裂纹的数量相对较少,且更容易沿预制裂纹尖端方向向外起裂;巴西圆盘试件在冲击荷载的破坏形式与预制裂隙长度密切相关,与裂隙宽度关联性较弱。

In order to investigate the mechanical properties and failure law of concrete specimens with cracks of different inclination angles under impact load,the split Hopkinson pressure bar(SHPB)was used to test concrete specimens,and a high-speed camera system was used to capture the crack growth and dynamic failure process in real time.Results show that the reflected wave amplitude of the crack specimens with 30°is relatively large,while the reflected wave amplitude of the crack specimens with 0°is relatively small.When the angle of the crack is 0°,the shock wave dissipation is less,and the transmitted wave amplitude is larger.When the angle of the prefabricated crack is 60°,the shock wave dissipates more,that is,when the angle between the stress wave propagation direction and the prefabricated crack is 60°,the specimen is most likely to fail.The newly formed cracks under impact load initiate,propagate,and coalesce along the precast crack tip on the whole,and the failure mode is mainly tensile failure under compressive stress.Under the same width of the prefabricated crack,the failure mode of the prefabricated crack with a length of 20 mm is simpler than that of the prefabricated crack with a length of 10 mm.The number of new cracks is relatively small,and it is easier to crack outwards along the direction of the prefabricated crack tip.The failure modes of Brazilian disc specimens under impact load are closely related to the length of prefabricated cracks,but weakly related to the width of cracks.