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1 工程地质条件大朝山水电站拦河大坝采用全断面碾压砼重力坝,最大坝高111m,拦河坝段坝顶长254m。基础灌浆于1998年9月开始施工,至今已完成固结灌浆45082.6m,帷幕灌浆8053.6m。大坝坝基基岩主要由三叠系上统玄武岩、玄武质火山角砾熔岩及凝灰岩组成。凝灰岩的抗压强度平均25MPa,岩性软弱,为大朝山水电站的原生软弱夹层。由于玄武岩坚硬完整,常沿凝灰岩的上、下界面形成顺层剪切带,形成构造型软弱夹层。基础为单斜构造,流层节理发育,流层产状 N60°～85°/E∠NW<25°～35°,沿凝灰岩夹层纯凝灰岩段顺层挤压明显。挤压带厚度基本与凝灰岩夹层等厚,部分凝灰岩泥化或糜棱岩化。主要有3组节理,即近 SN、NEE 和 NWW,节理一般延伸长度1～5m,间距20～50cm,节理多闭合,少数张开1～5mm。
1 Engineering Geological Conditions Dachaoshan Hydropower Station dam using full-face roller compacted concrete gravity dam, the maximum dam height 111m, barrage dam top length 254m. The foundation grouting started construction in September, 1998. Up to now, the consolidation grouting has reached 45082.6m and the curtain grouting has reached 8053.6m. The dam foundation bedrock is mainly composed of Triassic upper basalt, basaltic volcanic breccia lava and tuff. The compressive strength of tuffs is 25MPa on average with weak lithology, which is the native weak interlayer of Dachaoshan Hydropower Station. Due to the integrity and integrity of the basalt, strata shear strata often form along the upper and lower interfaces of the tuff to form structural weak intercalations. Based on the monoclinic structure, the knots of the flow strata developed with flow regimes of N60 ° ~85 ° / E∠NW <25 ° ~35 ° and were obviously squeezed along the tuff of the tuff interlayer. The thickness of the extruded belt is basically the same as the thickness of the tuff interlayer, and some tuffaceous or mylonized rocks. There are mainly three groups of joints, that is, near SN, NEE and NWW. The joint extension is generally 1 ~ 5m in length and 20 ~ 50cm in spacing. The joints are mostly closed and a few open 1 ~ 5mm.