Analysis of damage accumulating characteristics and vibration isolating effect of presplitting blasting in excavation of large-scale navigation lock
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摘要: 针对大型船闸预裂爆破开挖时中隔墩振动与损伤控制的问题,依托现场爆破试验,对比分析了不同段主爆孔诱发振动的峰值,采用数值模拟的方式,研究了不同段主爆孔的爆破累积损伤特性,分析了不同损伤范围下预裂缝的隔振效果,并对船闸爆破开挖方案进行了优化。研究结果表明:预裂爆破开挖中主爆孔爆破会对预裂缝附近岩体产生累积损伤,但会增强对后续主爆孔的隔振效果;随着预裂缝附近岩体累积损伤的增加,其隔振效果逐渐增强,并最终稳定在50%左右;爆破振动峰值(PPV)衰减幅度随着损伤宽度的增加而增加,当损伤宽度达到4 cm后,衰减幅度趋于平缓。大型船闸开挖中应综合考虑预裂爆破累积损伤特性及其隔振效果,可采用先拉槽增加侧向临空面与设置施工预裂缝的爆破开挖优化方案,进而保证开挖效果,并降低对保留岩体的扰动。Abstract: Controlling the blast-induced damage is of significance for the stability of division pier in the excavation of the large-scale navigation lock. Based on the on-site experiment, the peak particle velocities (PPV) induced by production boreholes were compared, and the damage evolution characteristics were analyzed with the help of the software LS-DYNA. Moreover, through the analysis of the on-site experiment results and numerical results, the blasting excavation scheme of the large-scale navigation lock was optimized. The research results indicate that the rock mass damage induced by production blast-holes will strength the pre-crack vibration isolating effect. With the increase of the width of the blast-induced damage zone, the vibration isolating effect is gradually increased, and finally stabilized at 50%. The attenuation rate of PPV increases with the width of blast-induced damage zone, and when the width of the damage zone reaches 4 cm, the attenuation rate gradually slows down. The damage cumulative characteristics induced by production and pre-splitting crack vibration isolation effect should be taken into consideration in the excavation of the large-scale navigation lock. Therefore, the optimizations of blasting excavation, including the cutting blasting and construction presplitting blasting, were put forward to reduce the blast-induced damage to reserved rock mass and optimize the blasting effect.
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表 1 炸药主要参数
Table 1. Parameters of explosive in numerical models
密度
/(kg·m−3)初始爆轰速度
/(m·s−1)初始爆轰压力/GPa A1/GPa B1/GPa R1 R2 ω 1 000.00 5 000.00 5.15 49.40 1.89 3.90 1.11 0.33 表 2 RHT模型主要参数取值
Table 2. Parameters used in the RHT model for rock
密度/(kg·m−3) 体积模量/GPa 剪切模量/GPa 抗压强度/MPa 损伤常数D1 损伤常数D2 完整失效面常数A 完整失效面指数N 2750.00 35.20 16.70 35.00 0.04 1.00 1.60 0.61 -
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