预裂爆破在水布垭枢纽趾板开挖中的应用

Application of presplit blasting in excavation for toe slab of concrete face rockfill dam at Shuibuya hydropower project

趾板开挖采用预裂控制爆破技术,通过搭设钻机作业的钢管架和间隔不耦合装药结构,严格控制钻孔方向、倾度和单孔装药量,避免了建基面出现欠挖和超挖量过大现象,预裂缝的形成降低了爆破震动影响,经爆破后检查,岩体完整性良好,无爆破裂隙,坡面不平整度均小于15cm,残留炮孔痕迹分布均匀,保存率超过85%,爆破效果良好,确保了趾板开挖质量优良,提高了经济效益。

Presplit blasting technology was used for the excavation of toe slab foundation of Shuibuya concrete face rockfill dam, in the blasting excavation process, excessive underexcavation and overexcavation were all avoided because of setting up some support frames with steel pipes for convenient drill operation, using an interval uncoupled explosive-charging structure, strictly controlling the direction and inclination of drilling and the per-blast hole explosive charge. The impact of blasting vibration was decreased due to the formation of presplit cracks. Inspection was conducted after blasting, results from inspection indicated that the preserved foundation rock showed up perfect integrity with no blasting fissures in it, the surface unevenness was less than 15 cm, the remaining traces of blast holes were uniformly distributed and the preservation rate of remaining blasthole traces was greater than 85%, resulting in good blasting effect and good excavation quality, raising economic benefit.