深埋隧洞钻爆开挖围岩振动频率特性研究

Vibration frequency characteristics of surrounding rock of deep tunnel induced by borehole-blasting

针对深埋圆形隧洞全断面毫秒延迟钻爆开挖,通过建立开挖面上地应力瞬态卸荷与爆炸荷载激发围岩振动的理论计算模型,并结合实测振动信号分析,研究了影响围岩振动频率的因素及其频谱特性。研究结果表明,瞬态卸荷持续时间、爆炸荷载上升时间和开挖面大小是影响深埋隧洞钻爆开挖围岩振动频率的主要因素;在爆源近区围岩振动以爆炸荷载作用为主,但爆炸荷载上升时间远小于瞬态卸荷持续时间,由此导致爆炸荷载激发振动的频率高,其质点峰值振动速度衰减快,在中远区地应力瞬态卸荷可成为引起围岩振动的主要因素;瞬态卸荷与爆炸荷载共同作用产生的振动具有两个优势频带,其低频成分主要由瞬态卸荷引起,而高频成分主要由爆炸荷载引起。

For a deep circular tunnel excavated by the full-face millisecond delay blasting, a two-dimensional mechanical model is firstly developed to calculate the vibration caused by dynamic loads in the process of rock blasting fragmentation. Dynamic loads include transient release of in-situ stress occurring on excavation faces and blast loading. By using this theoretical model and analyzing the vibration signals measured in the field, characteristics of the vibration frequency and their influence factors are subsequently studied. The results show that the vibration frequency in deep tunnel during blasting excavation is mainly affected by the duration of stress release, rising time of blast loading and the dimension of excavation faces. Rock vibration in the vicinity of blasting source is primarily caused by blast loading. Since the rising time of blast loading is much shorter than the duration of stress release, the vibration caused by blast loading thus has a higher frequency than that induced by the transient release of in-situ stress, andthe peak velocity of vibration attenuates faster with the distance. At the far distance, the vibration generated by the transient release of in-situ stress may become a primary component. It is also found that the vibration caused by the combined action of dynamic loads has two dominant frequency bands. The transient release of in-situ stress is mainly responsible for the low-frequency vibration, while the blast loading accentuates the high-frequency vibration.