大断面隧道钻爆冲击波的衰减规律

隧道开挖爆破产生的空气冲击波的破坏效应，将会对人员、机具设备与周围环境造成危害。隧道钻孔爆破冲击波的影响因素比裸露药包爆炸更多、更复杂，研究其衰减规律对采取合适的防护措施意义重大。本文中开展了时速350 km双线铁路大断面隧道钻孔爆破空气冲击波的现场测试，分析了不同工况下冲击波传播规律及影响因素。结果表明：钻爆冲击波超压时程曲线存在多个不同幅值的超压波峰，波峰之间具有明显微差延时的短间隔性，传播至远场未形成稳定的单一平面波，与单一药包爆炸冲击波的传播规律存在差异；钻爆冲击波超压信号由多段与微差延时相对应的子信号叠加而成，子信号数量与毫秒延期雷管段数相同，呈现出典型的时域特征；相同爆破条件下，大断面隧道钻爆时的乳化炸药冲击波转化因数小于小断面巷道工况下的；相较于总药量及最大段药量，按掏槽药量计算的超压峰值与实测超压峰值之间的相关性最强，钻爆冲击波最大超压峰值宜按掏槽段炸药TNT当量确定；隧道内大型机械设备等障碍物改变了钻爆冲击波流场的传播规律，呈现较明显的叠加放大效应。

Attenuation of blast wave in a large-section tunnel

The blasting air shock wave produced by tunnel excavation results in considerable casualties and damage to equipments and environments. Compared with those of the explosion of bare charges, the influencing factors of the blast wave induced by tunnel drilling are more complicated, so it is of considerable significance to study its attenuation law for taking appropriate protective measures. In this paper, a field test of blasting shock wave was carried out during the drilling and blasting of a large cross-section tunnel with a speed of 350 km/h, and the propagation law and influence factors of blasting shock wave under different conditions were analyzed. The results display that there are multiple overpressure peaks with different amplitudes in the shock wave overpressure-time curve, showing the short time intervals with significant millisecond delay characteristics between wave peaks. When the shock wave propagates to the far field, it does not form a stable plane wave, and it is different from the propagation law of shock wave of the single charge explosion. The shock wave overpressure signal is superimposed by multiple sub-signals, showing typical time domain properties, and the number of sub-signals is the same as that of the millisecond delay detonator segments. Under the same blasting conditions, the conversion factor of emulsion explosive energy into shock wave in a large-section tunnel is smaller than that in a small-section tunnel. Compared with the total charge and the maximum charge, the linear correlation between the peak values of shock wave overpressure calculated by the cut-hole charge and the measured peak values is the strongest. Then the maximum peak value of the blasting shock wave overpressure should be determined according to TNT equivalent of the cut-hole charge. Obstacles such as the large equipment in the tunnel will change the propagation law of the shock wave, showing a significant superimposed amplification effect.