多级复式楔形掏槽在大断面隧洞掘进中的应用研究

Application of Multi-level Double Wedge Cut in Large Section Tunnel Driving

在米易县马鞍山水库溢洪洞工程施工过程中,采用现有的爆破方案时,存在钻孔利用率低、掘进速度慢、爆破效果差、爆后有大量残孔及大体积根底等问题,且周边孔半孔率不足60%。基于此,提出了"多级复式分部楔形掏槽"的解决方案。提高循环进尺,并实施五级掏槽设计,即内掏槽孔、主掏槽孔及3排辅助掏槽孔;优化周边孔参数,采用间隔装药结构,降低线装药密度及单孔装药量。通过9次爆破试验后,炮孔利用率达到96.8%;爆后无残孔及根底;周边孔半孔率达到90%以上。通过试验发现,特别是在大断面硬岩隧道开挖困难时,采用多级楔形掏槽能有效的扩大掏槽腔体体积,增强掏槽效果;分部设计在减少穿孔数量的同时,还保证了优良的爆破效果。

In the process of spillway tunnel construction in Ma＇an Mountain reservoir in Mi Yi County, some problems came into being, such as lower utilization ratio of drilling hole and slow advance speed of tunnel, where the average drilling utilization ratio is only 75.6%. Secondly, poor blasting effect resuhed in large amount of residual holes and large volume of foundation. Thirdly, half-borehole rate was less than 60%. Then, the muhi-level double wedge cut solution was proposed. By increasing the excavation cycle footage, applying 5 stage cutting design, optimizing parameters of peripheral hole and interval charge, decreasing the linear charge density and the charge quantity, good blasting effects were obtained, such as the blasting hole utilization ratio reached up to 96.8% ,no residual hole and foundation existed anymore and the half-borehole rate exceeded above 90%. Results show that,on the condition of large section of hard rock tunnel excavation, the multi-level segment wedge cutting is highly effective in expanding cutting cavity, which further reduces the hole numbers but also ensures good blasting effect.