隧道爆破震动对新喷混凝土的累积损伤计算

为减少隧道爆破震动对初衬喷射混凝土的损伤,通过现场质点震速监测和信号分析,根据爆破动力学理论,探讨混凝土龄期对累积损伤的影响。综合考虑质点震速、初始损伤、混凝土强度和龄期等因素,提出单次爆破对混凝土的损伤增量及多次爆破对混凝土的累积损伤的计算方法。研究结果表明:混凝土的破坏是一个损伤的累积过程,单次爆破的损伤增量超过增量阈值并不一定造成材料的破坏;在混凝土中掺入早强剂有显著减震效果。将该方法应用于工程实例,提出新喷混凝土的爆破安全准则。

Cumulative Damage Evaluation of Young Shotcrete in Tunnel Caused by Blast-induced Vibration

In order to decrease the damage of young shotcrete caused by blast-induced vibration in tunnels,effect of age on damage cumulation of concrete was studied based on the theory of blasting dynamics,field signal monitoring and analyzing of particle velocities.A calculating method was put forward to evaluate the damage increment caused in a single blasting action and also the damage cumulated in the past blasting actions.The vibration velocity of particles,the initial damage of young shotcrete,the strength and the age of the concrete were comprehensively considered in the method.The results show that the failure of shotcrete is a damage cumulation process;and the failure does not always occur though the damage increment exceeds its threshold in a single blasting action.Mixing early-strengthening agent with concrete is helpful in reducing the vibration effect.At the same time,the method was applied to an engineering case and blasting safety criteria for young shotcrete were suggested.