预裂爆破在洪家渡水电站左坝肩开挖中的应用

Application of presplit blasting in left abutment excavation of Hongjiadu hydropower project

贵州洪家渡电站位于贵州毕节地区织金县与黔西县交界的六冲河上,该电站地层岩性为灰岩和泥页岩相间,岩石普氏硬度系数为6～8。其中的左坝肩为垂直陡高边坡,溶洞发育、地形陡峭、场地狭窄、环境复杂、高差大,致使开挖难度很大,该工程要求预裂面无欠挖,超挖小于20cm,基础面高程开挖偏差不大于±20cm,孔向偏差小于0.5°,通过采用预裂爆破技术,严格控制钻孔精度和爆破参数,顺利地完成了坝肩开挖任务,保证了施工质量和安全。

Hongjiadu Hydropower Station is located on the Luchong River between Zhijin County and Qianxi County in Bijie Prefecture, Guizhou Province. The strata at the station are alternative limestone and argillaceous shale, with their Protodikonov's hardness coefficient being 6-8. The left abutment is characterized by high and precipitous slopes, developed karst caves, steep topography, narrow work site, complicated circumstances, etc., resulting in great difficulty in excavation. The project design stipulated that no underexcavation on presplit surfaces was permissible, the overexcavation was limited within 20 cm, the elevation difference of the foundation rock surface should be between +20 cm and - 20 cm, and the direction deflection of boreholes should be less than 0.5°. By means of presplit blasting technology and strictly controlling the accuracy of drilling, and blasting parameters, the task of secondly-hard rock excavation was smoothly fulfilled and construction quality and safety were ensured.