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.