观音岩水电站坝址区右岸岩体溶蚀发育机理研究

观音岩水电站位于金沙江上游,坝型初拟混凝土重力坝和心墙堆石坝组合坝。坝址区分布有侏罗系中蛇店组(J2s)地层,岩性主要为钙质铁质胶结的砾岩、石英砂岩,其中砾石成分以泥晶灰岩和生物灰岩为主。在地下水作用下砾岩钙质溶蚀形成规模较大的囊状空腔或孔洞,砂岩则表现为钙质胶结物流失溶蚀呈砂土状或砂糖状,对坝基稳定性造成了一定的影响。本文在对观音岩水电站坝址区右岸地质条件和水文地质条件分析的基础上,采用地下水动力模拟、可溶成分统计、取样室内溶蚀试验等方法对岩体溶蚀发育机理进行了分析。结果表明:岩体溶蚀作用主要受岩性、构造控制; 由于局部地下水流循环快,流速较大,顺节理裂隙的走向方向溶质作用强烈; 钙质胶结的砾岩、含砾砂岩中,钙质砾石碎屑含量占30％ ~50％; 新鲜岩石易受溶蚀且溶蚀速度较快。研究成果为进一步对大坝抗滑、变形及渗透稳定性的影响评价奠定了基础,同时为水库蓄水后地下水对岩体溶蚀作用的研究提供了背景。

CORROSION MECHANISM OF ROCK MASS AT DAM SITE LEFT BANK OF GUANYINYAN HYDROPOWER STATION

The Guanyinyan Hydropower Station locates in the upper reaches of Jinsha River.The dam type is a combination of concrete gravity dam and core rockfill dam.The stratum in the dam site is middle Shedian group of Jurassic.The lithology is mainly the calcareous ferruginous cemented conglomerate and the quartz sandstone.The main components of conglomerate are cryptite and biolithite.The large cystic cavities or holes are formed by corroded calcareous ferruginous under groundwater.The corroded calcareous cement in sandstone displays sand-like or sugar-like.So it affects the stability of dam foundation.On the basis of analyzing geological conditions and hydro-geological conditions in the right bank of the station,this paper investigates the groundwater-dynamic simulation,water-soluble element statistics and corrosion experiment of sampling for rock corrosion rules.It is found that the rock and tectonic control play a leading role for the rock corrosion.The solute reaction is developed intensely along strike direction of joints and fractures,because of local-groundwater with quick circle and rapid flow rate.Not only the agglutination of the sandy and gravelly rock is calcareous,but also 30％ ~50％of the gravel is calcareous.So the dissolubility of the rock is strong.The fresh rock surface is easily corroded,and the corrosion rate is fast.The research results can serve as the foundation for antiskid,distortion and seepage stability evaluation.They also provide background information for the study to erosion-dissolution of rock with groundwater after impounded water.