大跨度小净距隧道中夹岩爆破振动控制与损伤判别

Blasting Vibration Control and Damage Determination of Interlaid Rock in a Tunnel with Large Spans and Short Distances

明确爆破动载作用下大跨度小净距隧道中夹岩柱的振动响应及累积损伤演化规律,有助于更好地保障隧道现场施工及围岩稳定。依托厦门海沧疏港通道工程项目,现场采用爆破测振与声波测试对中夹岩体的爆破振动速度及围岩声波速度进行监测与分析,并对原有的爆破方案进行优化,对循环爆破作用下中夹岩振动传播与损伤演化规律进行探究。研究结果表明:1)掏槽眼的装药量和自由面数量是影响中夹岩爆破振动速度的主要因素,通过优化爆破方案设置减振孔,使中夹岩振速降低了67.4%,最终控制中夹岩的最大质点峰值振动速度为12.67 cm/s,符合规范要求;并根据萨道夫斯基公式,回归得到中夹岩的振动响应规律。2)在多频次爆破作用下,侧面岩体声波速度整体高于中夹岩体,受应力波及裂隙的共同影响,围岩声波速度由中夹岩内部至隧道轮廓线呈波动式下降趋势,随着掌子面的不断远离,中夹岩累积损伤范围最终稳定在距围岩表面1.5 m范围内;通过现场监测与优化实现中夹岩爆破振动控制与累积损伤范围判定,保障了大跨度分岔隧道的高效安全掘进。

Clarifying the vibration response and cumulative damage evolution law of an interlaid rock column in a large span tunnel with a small clear distance under dynamic blasting loads can better ensure the tunnel construction and stability of surrounding rock. Hence, a case study is conducted on the Xiamen Haicang Shugang channel project, where onsite blasting vibration measurement and acoustic wave test are adopted to conduct monitoring and analysis on the blasting vibration and borehole wave velocity of the interlaid rock in the small clear distance section, and the original blasting plan is optimized. Furthermore, the law of vibration propagation and damage evolution of the interlaid rock under the effects of cyclic blasting is explored. The results show the following:(1) Amount of charging of the cut and the number of free surfaces are the main factors affecting the vibration velocity of the interlaid rock blasting. The vibration velocity of the interlaid rock is reduced by 67.4% by optimizing the vibration reduction hole setting in the optimized blasting scheme, and the maximum mass peak vibration speed of the interlaid rock is 12.67 cm/s, which conforms to the specification requirements. According to the Sadowski formula, the vibration response law of the interlaid rock is obtained.(2) Under multifrequency blasting, the acoustic wave velocity of the side rock mass is higher than that of the middle rock mass. Due to the combined effects of stress wave and cracks, the wave velocity of surrounding rock shows a fluctuating downward trend from the inside of the interlaid rock to the tunnel contour. When moving away from the tunnel face, the cumulative damage range of the interlaid rock is eventually stabilized within 1.5m of the surrounding rock surface. Through onsite monitoring and optimization, the blasting vibration control of the interlaid rock and the judgment of the cumulative damage range are realized, which ensures efficient and safe excavation of large-span bifurcated tunnels.