光面爆破在卡鲁玛尾水隧洞开挖中的改进与应用

Improvement and application of smooth blasting used in excavation in Karuma HPP TRT project

在乌干达卡鲁玛尾水隧洞8#支洞Ⅲ类围岩开挖中,为了解决光面爆破施工中用的25mm细药卷短缺、绑扎光面爆破药串用的竹片无法买到等问题,采用了经过加工的32mm常规药卷,调整了光面爆破孔内装药结构和装药方法,并在选用常规周边光面爆破孔孔距条件下,适当减小光面爆破层厚度,将周边光面爆破孔密集系数提高到1.25~1.43。爆破实践表明：通过一系列改进,即便在只有最常见的32mm常规药卷和导爆索条件下,仍能取得良好的光面爆破效果。这一改进简化了光面爆破药串加工工序,减少了光面爆破层脱落需要克服的阻力,减轻了爆破对洞周被保留岩体的伤害。

During tunnel excavation of class Ⅲ wall rock in adit-8 of Karuma HPP TRT project, in order to resolve the problems like φ25 mm cartridge lacking and unavailableness of bamboo chips for fixing cartridge. The φ32 mm normal cartridge was used in smooth blasting. Charging structure and method were adjusted, the thickness of smooth blasting layers was de- creased and density coefficient of periphery borehole was increased to 1.25-1.43 on condition of normal spacing of periphery boreholes. The blasting effect showed that the smooth blasting could achieve satisfactory result even only using φ32 mm normal cartridge and prim cord. The cartridge processing was simplified, the residence to the falling of the smooth blasting layers was reduced, and the harms to the preserved rock body were relieved through the improvement.