预留核心土法隧道爆破围岩损伤与振动特性研究

Study on Damage and Vibration Characteristics of Surrounding Rock under Tunnel Blasting by Reserved Core Soil Method

目的 研究预留核心土法爆破开挖影响下的山岭隧道围岩损伤与振动特性,为爆破参数优化以及隧道加固设计提供理论参考。方法 依托新疆阿克特蒲2号左洞隧道工程,借助ANSYS/LSDYNA软件建立隧道爆破开挖数值模型,基于现场实际开挖轮廓和振速监测数据验证数值模型的合理性,进而分析围岩累积损伤特性、振速分布和振速衰减规律。结果 爆破结束后,隧道轮廓平整,预留核心土上部损伤严重;隧道拱顶y方向、拱肩z方向及拱脚x方向的振速最大;距离掌子面越近,采用萨道夫斯基经验公式预测的振速结果误差越大。结论 为保证结构稳定性,在下次爆破施工前可以通过减少掏槽孔、辅助孔的装药量或者调整其孔网参数来减小爆炸荷载,沿最大振速方向进行重点加固;采用萨道夫斯基经验公式预测距离掌子面10 m内的振速时,避免仅用z方向距离近似为爆心距大小,应同时考虑三个方向的距离。

The damage and vibration characteristics of mountain tunnel surrounding rock under the influence of reserved core soil blasting method are studied to provide theoretical reference for blasting parameter optimization and tunnel reinforcement design.Based on the left tunnel project of Aktepu No.2 in Xinjiang,the numerical model of tunnel blasting excavation is established with ANSYS/LSDYNA software.The rationality of the numerical model is verified based on the actual excavation contour and vibration velocity monitoring data,and then the cumulative damage characteristics,vibration velocity distribution and attenuation law of surrounding rock are analyzed.After blasting,the outline of the tunnel is smooth,and the upper part of the reserved core soil is seriously damaged.The vibration velocity of tunnel arch vault in y direction,spandrel in z direction and arch foot in x direction is the largest.The closer the distance to the tunnel face,the greater the error of the vibration velocity predicted by Sadowski′s empirical formula.In order to ensure the stability of the structure,before the next blasting construction,the explosive load can be reduced by reducing the cut hole,the auxiliary hole charge or adjusting the hole network parameters,and the emphasis is placed on strengthening along the direction of the maximum vibration velocity.In the application of Sadowski′s empirical formula to predict the vibration velocity within 10 m from the tunnel face,it is important to avoid approximating the size of the burst center distance by the distance in the z direction alone.Instead,it is necessary to consider the distances in all three directions simultaneously.