True triaxial rockburst experiments with four different unloading rates were performed on four prism specimens of granite sampled from Beishan, China. The damage evolution in the rockburst test was investigated from t...True triaxial rockburst experiments with four different unloading rates were performed on four prism specimens of granite sampled from Beishan, China. The damage evolution in the rockburst test was investigated from two aspects including fracture surface crack and fragment characteristics. The scanning electron microscopy was used to observe the micro crack information on fragment surface. Combing binarization and box counting dimensions, the fractal dimensions of cracks were obtained. Meanwhile,the fragments were collected and a sieving experiment was conducted. We weighed the fragments qualities, counted the amount of fragments and measured the fragments length, width and thickness.Utilizing four methods to calculate damage fractal dimensions of fragments, the trend of fractal value changing with unloading rates can be roughly described. It can be concluded from these experiments that the fractal dimension either for crack or for fragment holds a decreasing trend with the decreasing unloading rate, indicating a reduction of damage level.展开更多
利用深部岩爆模拟试验系统对花岗岩进行室内瞬时岩爆模拟试验,同时利用声发射系统采集试验过程中声发射信号,得到试验全过程应力和声发射波形信息时域图。结合声发射累计能量曲线特征,找到5个关键拐点,即花岗岩初始加载能量激增后产生...利用深部岩爆模拟试验系统对花岗岩进行室内瞬时岩爆模拟试验,同时利用声发射系统采集试验过程中声发射信号,得到试验全过程应力和声发射波形信息时域图。结合声发射累计能量曲线特征,找到5个关键拐点,即花岗岩初始加载能量激增后产生的第一个拐点A、岩爆发生前两次明显的上升台阶处拐点B和C、岩爆发生时的能量突跃点D、最终峰值点E。将关键点处波形信号从全时域波形中提取出来并进行快速傅里叶变换,得到各关键点二维功率谱图,结果表明:花岗岩声发射主频值在加载初期时为106 k Hz,随着荷载的增加,频率由低频向高频过渡,频带变宽且由单峰向多峰转化,频率成分复杂预示多种破裂模式的发生。岩爆前和最终岩爆时刻频带又变窄并恢复单峰,主频值降低至与初始加载时一致,约为106 k Hz,预示着岩爆时刻花岗岩岩石高能量的释放。展开更多
基金supported by the National Key Basic Research Program (No. 2010CB226800)the Innovation Team Development Program of the Ministry of Education (No. IRT0656)the Fundamental Research Funds for the Central Universities (No. 2010YL14)
文摘True triaxial rockburst experiments with four different unloading rates were performed on four prism specimens of granite sampled from Beishan, China. The damage evolution in the rockburst test was investigated from two aspects including fracture surface crack and fragment characteristics. The scanning electron microscopy was used to observe the micro crack information on fragment surface. Combing binarization and box counting dimensions, the fractal dimensions of cracks were obtained. Meanwhile,the fragments were collected and a sieving experiment was conducted. We weighed the fragments qualities, counted the amount of fragments and measured the fragments length, width and thickness.Utilizing four methods to calculate damage fractal dimensions of fragments, the trend of fractal value changing with unloading rates can be roughly described. It can be concluded from these experiments that the fractal dimension either for crack or for fragment holds a decreasing trend with the decreasing unloading rate, indicating a reduction of damage level.
文摘利用深部岩爆模拟试验系统对花岗岩进行室内瞬时岩爆模拟试验,同时利用声发射系统采集试验过程中声发射信号,得到试验全过程应力和声发射波形信息时域图。结合声发射累计能量曲线特征,找到5个关键拐点,即花岗岩初始加载能量激增后产生的第一个拐点A、岩爆发生前两次明显的上升台阶处拐点B和C、岩爆发生时的能量突跃点D、最终峰值点E。将关键点处波形信号从全时域波形中提取出来并进行快速傅里叶变换,得到各关键点二维功率谱图,结果表明:花岗岩声发射主频值在加载初期时为106 k Hz,随着荷载的增加,频率由低频向高频过渡,频带变宽且由单峰向多峰转化,频率成分复杂预示多种破裂模式的发生。岩爆前和最终岩爆时刻频带又变窄并恢复单峰,主频值降低至与初始加载时一致,约为106 k Hz,预示着岩爆时刻花岗岩岩石高能量的释放。