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利用改进的分离式霍普金森压杆(SHPB)系统,对花岗岩进行多次循环冲击压缩试验,并结合岩石声发射监测研究花岗岩在动态冲击下的累计损伤特性。利用超动态应变仪获取的波形信号分析试样中的纵波通过时间,进而计算岩石的应力波波速,并利用花岗岩应力波波速的变化来表征试样在循环冲击过程中的损伤特性。通过分析试样每次加载过程中的能量变化,发现多次冲击加载过程中的岩石损伤量变化程度与试样在单次加载过程中的吸收能大小有关,试样的吸收能越大,花岗岩冲击后的损伤变化量越大。花岗岩在多次冲击加载过程中的动态抗压强度随着冲击次数的增多而减小,但随加载应变率的增大而增大。基于冲击加载过程中的应力时程曲线及声发射信号特征,发现声发射事件峰值计数随着加载次数的增多而增大,表明花岗岩在多次冲击过程中新生裂纹在逐渐增多,花岗岩在每次加载过程中的声发射事件峰值点位于试样应力峰值点附近,且其在动态冲击下的声发射事件具有突发性,前兆信息不明显的特点。
By using the improved split Hopkinson pressure bar (SHPB) system, the cyclic impact compression test of granite was carried out. Combined with the acoustic emission monitoring of granite, the cumulative damage characteristics of granite under dynamic impact were studied. Using the waveform signal acquired by the ultra-dynamic strain gauge, the compressional wave velocity of the rock is calculated by analyzing the passage time of the compressional wave and the damage characteristics of the sample during the cyclic impact are characterized by the change of wave velocity of the granite. By analyzing the energy change during each loading process, it is found that the degree of rock damage during multiple impact loading processes is related to the energy absorbed by the sample in a single loading process. The larger the absorption energy of the sample, the more the granite Impact changes after injury greater. The dynamic compressive strength of granite during multiple impact loading decreases with the increase of impact times, but increases with the increase of loading strain rate. Based on the stress history and the characteristics of acoustic emission signals during impact loading, it was found that the peak counts of acoustic emission events increased with the increase of loading times, which indicated that the number of new cracks in granite increased gradually during multiple impacts. During the loading process, the peak of acoustic emission event is near the peak of sample stress, and the acoustic emission event under the dynamic impact is sudden with the precursor information is not obvious.