黄登水电站坝基一次性开挖爆破施工技术

Construction Technology of Disposable Excavation Blasting for Dam Foundation in Huangdeng Hydropower Station

黄登大坝坝基河床深窄,水面高程以下开挖高度达53m,坝基底部宽度65m,覆盖层深厚内含丰富水量,基岩透水量大,自上而下分布有顶部开挖下江的大孤石层、砂砾石层、基岩层;基岩出露高程距大坝建基面平均6~8m,水平建基面积达9742m^(2)以上,水平预裂造孔量大;开挖工作面狭小,施工道路和大型设备布置困难,机械设备效率低;要满足大坝混凝土浇筑工期要求,开挖工期紧,强度高;为了保证坝基开挖进度和建基面质量,基岩6~8m采用水平预裂一次开挖爆破成型技术,取得了成功。

The river bed of the dam foundation of Huangdeng Dam is deep and narrow,the excavation height below the water surface elevation is 53m,and the width of the dam foundation is 65m.The overburden layer is deep and contains plenty of water,and the permeability of the bedrock is large.From top to bottom,there are large boulders,gravel layers and bedrock layers of the lower river excavated at the top.The exposed elevation of bedrock is 6-8m from the dam foundation surface on average,the horizontal foundation area is over 9742m2,and the horizontal pre-splitting pore-forming quantity is large.The excavation working face is narrow,the construction road and large equipment are difficult to arrange,and the efficiency of mechanical equipment is low.To meet the requirement of concrete placing construction period of dam,the excavation period is tight and the intensity is high.In order to guarantee the excavation progress and quality of foundation surface,the horizontal pre-splitting blasting technology of one excavation is used for 6-8m bedrock,which has achieved success.