白鹤滩水电站左岸地下厂房岩锚梁爆破试验参数研究

Study on blasting test parameters of rock anchor beam in left-bank underground powerhouse of Baihetan Hydropower Station

为了解不同爆破条件下的爆破振动特性及传播规律,保证白鹤滩水电站三大洞室边墙开挖质量,特别是岩锚梁岩台的开挖质量,根据三大洞室特点与相关技术要求,结合现场实际情况及施工实施计划,拟在厂房第Ⅱ、Ⅲ层进行岩锚梁保护层及岩台开挖爆破试验、爆破振动效应试验,为确定科学的爆破控制方案、钻爆参数及施工工艺提供基本依据。结合爆破振动观测与岩体声波检测成果,确定如下岩锚梁开挖参数:(1)厂房岩台梁3 m层厚保护层光爆孔距为0.5 m,线装药密度为93 g/m;(2)厂房岩锚梁光爆孔距为35 cm,垂直光爆孔线装药密度为58 g/m,斜光爆孔线装药密度为85 g/m。厂房岩锚梁层开挖按"平面分6区、立体分3层、弱爆破(梯段10 m、光爆15 m)、强支护(初喷跟进掌子面、锚杆不迟于两个爆破循环)"的原则实施,左岸厂房上、下游岩锚梁812 m全部开挖成型,质量优良。

In order to find out the characteristics of blasting vibration and the propagation law under various blasting conditions and ensure the excavation qualities of the side-walls of the three large caverns of Baihetan Hydropower Station,especially the excavation qualities of the rock benches for the rock anchor beams therein,the blasting test for the excavation of the protective layer and the rock bench and the test on the blasting vibration effect are planned to be carried out on the second and third floors of the powerhouse in accordance with the characteristics of the three large caverns and the relevant technical requirements on the basis of the in situ actual condition and the construction implementation scheme concerned,so as to provide the basic foundations for determining scientific controlled blasting scheme,drilling-blasting parameters and construction technologies. Combined with the results from the blasting vibration observation and the rock mass acoustic testing,the following parameters for the excavation of the rock anchor beam are determined:( 1) the smooth blasting borehole space for the excavation of the protective layer with the thickness of 3 m for the rock bench beam in the powerhouse is 0. 5 m with the linear charge density of 93 g/m;( 2) the smooth blasting borehole space for the excavation of the rock anchor beam is 35 cm with the linear charge density of 58 g/m for the vertical smooth blasting hole and the linear charge density of 85 g/m for the inclined smooth blasting hole. The excavation of the level for the rock anchor beam in the powerhouse is implemented under the principle of dividing into 6 zones in plane,three-dimensionally dividing into three layers,weak blasting( step of 10 m and smooth blasting of 15 m),strong support( the initial spraying concrete follows the excavating face,while anchor-bolt is made not beyond two blasting cycles.),and then all the upstream and downstream anchor beams with the total length of 825 m in the powerhouse are formed through the excavation with excellent qualities.