冲击载荷作用下层状岩石破碎能耗及块度特征

Broken energy dissipation and fragmentation characteristics of layered rock under impact loading

  • 摘要: 采用分离式霍普金森压杆(SHPB)试验装置,对0°,22.5°,45°,67.5°和 90°五种不同层理倾角的层状岩石进行了不同冲击速度下的动态压缩试验,对破碎后的试样碎屑进行筛分,对比分析了层状岩石动态破坏时的块度分布特征;探讨了不同入射能对层状岩石反射能、透射能、耗散能密度和块度分布的影响。结果表明:对同一层理倾角试样,随着冲击速度增大,块度平均粒径逐渐减小,破碎程度逐渐增大;相同冲击速度下层理倾角为67.5°的试样破碎程度最大,0°试样破碎程度最小。分形维数可以很好的量化表征破碎块度分布特征,破碎块度越小,分形维数越大。相同入射能时,90°试样耗散能密度最大,0°或22.5°耗散能密度较小,表明高倾角试样能量利用率高,0°或22.5°的利用率较低。层理倾角为45°,67.5°和90°的试样在入射能相同时反射能较大,层理倾角为0°,22.5°的试样透射能较大,表明大倾角下无用功大多以反射波形式耗散,低倾角下无用功大多以透射波形式耗散;反射能、透射能与耗散能密度随入射能增大而增加;分形维数随耗散能密度增大而增大。高倾角时随能耗增大,试样破碎程度越剧烈;低倾角随耗散能密度增大,试样破碎趋势变化较小,产生新裂纹与破裂面所需能量较多。在实际工程中,选择45°~67.5°倾角的动态加载角度,不仅岩石强度较低,岩石破碎程度高,且能量利用率较高。

     

    Abstract: By using split Hopkinson pressure bar ( SHPB) test apparatus,the dynamic compression tests of layered rocks with different bedding dips of 0°,22. 5°,45°,67. 5° and 90° under different impact velocities were carried out in this study. The fragmentation distribution characteristics of layered rocks were compared and analyzed according to sie- ving the crushed sample debris. The reflection energy,transmission energy,dissipated energy density and fragmentation under different incident energies were discussed. Results show that for the sample with same bedding dip angle,the av- erage particle size gradually decreases as the impact velocity increases. At the same impact velocity,the fracture degree of the specimen with a dip angle of 67. 5° is the largest,and the 0° sample is the smallest. Fractal dimension can quantitatively characterize the fragmentation distribution characteristics. The fractal dimension is larger when the frag- mentation is smaller. At the same incident energy,the dissipation energy density of the 90° sample is the largest,while the dissipation energy density of specimens with 0° or 22. 5° dip angle is smaller,which reveal that a high dip angle has a higher energy utilization rate,and 0° or 22. 5° is lower. At the same incident energy,the 90° samples have higher reflective energy,and the layered rocks with 0° and 22. 5° dip angles have higher transmission energy,which indicates that the reactive power dissipates mostly in the form of reflection waveform at high dip angle and mostly in the form of transmission waveform at low dip angle. The reflection energy,transmission energy and dissipation energy density in- crease with the increase of incident energy. The fractal dimension increases with the increase of dissipation energy den- sity. With the increase of energy consumption at high dip angle,the sample breaks more severely. With the increase of dissipated energy density at low dip angle,the trend of sample fragmentation changes little,and the energy required to produce new cracks and fracture surfaces is high. In engineering practices,if the dynamic loading angle of 45. 0° -67. 5° is selected,not only the strength of rock is low,and the rock sample breaks more severely,but also the energy u- tilization rate is high.

     

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