平寨坝址左岸岩溶发育规律及其对建坝条件的影响

地层岩性、水文地质、地质构造对平寨坝址的工程地质条件起着主要作用。从岩溶形态入手 ,对平寨坝址左岸岩溶的分布规律进行了研究 ,指出主要岩溶形态如洼地、漏斗、落水洞等在平面上呈带状分布 ;溶洞在垂向上具成层性、空间展布上具方向性以及平面分布具差异性等分布规律。对影响岩溶发育的因素进行了探讨的结果表明 :(1)灰岩的纯度越高、岩层越单一、层理的厚度越大 ,岩溶越发育 ;(2 )褶皱控制岩溶系统整体发育的方向、控制溶洞发育部位、规模及形态 ;(3)裂隙的发育程度和延伸方向决定岩溶发育的程度和发展方向。在岩溶发育规律的基础上对坝址左岸岩溶进行了如下预测 :(1)坝址左岸表层岩溶发育较强 ,岩体内部发育较弱 ;(2 )在坝轴线附近隐伏大规模溶洞的可能性较小 ;(3)平寨坝址河床深岩溶不发育。最后探讨了岩溶发育对建坝可能产生的渗漏与稳定性降低等问题

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.