KARST DEVELOPMENT AT THE LEFT BANK OF THE PINGZHAI DAM SITE AND ITS INFLUENCES ON CONSTURCTION OF THE DAM

This paper first characterizes geological conditions including stratigraphic lithology, hydrology and tectonic structures at the Pingzhai damsite. The authors then analyze distribution of karst caves at the left bank of the Pingzhai dam site based on morphology of karst. The results indicate that depressions, corroded funnels and sinkholes occur in a band distribution horizontally, and multiple stratifications vertically. The distribution of karst caves has a strong orientation in three dimensions. The following results are also obtained: (1) The purer the carbonate is and the thicker the bedding is, the more karst caves develop; (2) The folds control not only the direction of the karst development, but also the location, scale and configuration of karst caves; (3) The intensity and the extension of fracture development control the intensity and extension of karst development. At the end, the authors assess the potential development of karst caves at the left bank and its influence on the leakage and instability of the dam site: (1) The karst will develop extensively at the bank surface, but not inside the bank; (2) The potential for large cave development near the dam axis is very small; (3) The potential for karst development below the river bed is also very small.