Study on the Behavior of Blasting Crack Propagation under Different Crack Widths
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摘要: 为探讨炮孔不同割缝宽度对爆生裂纹动态扩展行为的影响，采用数字激光动态焦散线实验系统和分形理论，研究了6种不同割缝宽度时爆生裂纹的扩展规律。结果表明：割缝方向的爆生裂纹长度均大于非割缝方向的爆生裂纹长度；随着割缝宽度的增加，爆生裂纹扩展长度呈现先增大后减小的变化趋势；当割缝宽度增加到0.4 mm时，主裂纹扩展长度最大，割缝宽度继续增加后，主裂纹扩展长度减小。当割缝宽度为0.2 和0.4 mm时，分形维数较其他割缝宽度更大，爆生主裂纹的扩展长度较其他宽度下的扩展长度更长，试件定向断裂效果更优。随着割缝宽度的增加，割缝主裂纹的扩展应力强度因子和速度峰值呈现先快速降低再增加至二次峰值，最后振荡下降的变化趋势。割缝宽度为0.2和0.4 mm时，主裂纹应力强度因子的峰值和扩展速度峰值较其他割缝宽度更大。研究成果可为实际爆破工程中的割缝参数选择提供依据。Abstract: To study the influence of slit width on the dynamic propagation behavior of blast cracks, the digital laser dynamic caustic line experimental system and fractal theory were used to study the propagation laws of blast cracks at six different crack widths. The results show that the length of burst cracks in the cut direction is greater than that in the non-cut direction. With the increase of the slit width, the propagation length of burst crack increases first and then decreases. When the slit width increases to 0.4 mm, the main crack propagation length is the largest, and when the slit width continues to increase, the main crack propagation length decreases. When the slit width is 0.2 and 0.4 mm, the fractal dimension is larger than that of other slit widths, the expansion length of the main crack is longer than that of other widths, and the directional fracture effect of the specimen is better. With the increase of the slit width, the stress intensity factor and velocity peak value of the main crack propagation of the slot shows a trend of first decreasing rapidly, then increasing to the secondary peak, and finally oscillating and decreasing. When the crack width is 0.2 and 0.4 mm, the peak value of the stress intensity factor and the expansion velocity of the main crack are larger than those of other crack widths. The research results provide a certain basis for the selection of slit parameters in actual blasting engineering.
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Key words:
- dynamic caustic lines /
- crack propagation /
- stress intensity factor /
- box dimension
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图 2 动焦散实验系统实物照片和原理示意图
Figure 2. Photo and schematic diagram of the dynamic caustic experimental system
图 4 不同割缝宽度（0.1、0.2、0.4、0.6、0.8、1.0 mm）试件的爆后裂纹分布
Figure 4. Crack distribution of specimens with different slit widths (0.1, 0.2, 0.4, 0.6, 0.8, 1.0 mm) after blasting
图 6 割缝左侧焦散斑直径-时间演化曲线
Figure 6. Diameter-time evolution curves of caustic speckle on the left side of slit
图 7 试件左侧裂纹尖端的应力强度因子
Figure 7. Stress intensity factor at the crack tip on the left side of the specimen
图 9 不同割缝宽度下左侧裂纹的扩展速度-时间曲线
Figure 9. Velocity-time curves of left crack propagation under different slit widths
$ {E}_{\mathrm{d}} $/GPa $ \mu_{\mathrm{ }} $ |$ c $|/(m2·N−1) $ c_{\mathrm{p}} $/(m·s−1) $ {c}_{\mathrm{s}} $/(m·s−1) 6.10 0.31 0.88×10−10 2320 1260 
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表 2 裂纹的扩展长度
Table 2. Propagation lengths of the crack
L/mm Crack length/mm Left Right 0.1 41.4 41.3 0.2 63.5 64.0 0.4 69.0 73.0 0.6 57.2 46.2 0.8 38.4 40.0 1.0 39.7 37.4
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