湖南溶洼类型与水库坝线定位

KARST DEPRESSION TYPES AND DAM AXIS LOCATION IN HUNAN PROVINCE

溶洼按其发育阶段及其形态特征可分为幼年—雏型期、壮年—定型期、老年—破坏期、衰亡—残垣期。这些溶洼分别发育在相对的上升区与相对的下降区，其间岩溶管道虽说普遍存在，但因后期淤塞、水力坡降的变化而形成不同的成库条件与坝线定位条件。在上升区以暗河段上岩溶管道中的“卡脖子”的坝线最优，下降区则以明流段上的非可溶岩分布区最佳。实践表明水库渗漏主要由坝址区浅部的溶管与溶隙引起，而渗漏量的大小则与坝线所在溶洼水文网中的部位密切相关。因此综合考虑这些因素是溶洼水库坝线定位的关键问题。

Karst depressions can be classified as those of young,mature,old and die-away stages. They usually develop either in relatively uplifted or in relatively subsided areas.Althoughkarst conduits widely exist in these areas, different conditions for reservior construction anddam axis location may be formed due to siltation and change in hydraulic gradient.The opti-mal dam site is to be found at the“blocking neck”of karst pipe over a subterranean river inuplifted area, or at surface river bed section developed in nonsoluble rocks in subsided area. Reservior leakage is commonly attributed to solutional pipes and fissures in the shallow zonearound dam site. The amount of leakage is dependent on a large extent where the dam axis islocated in the hydrographic net of karst terrain,Therefore,synthetical consideration of thesefactors is critical in selection of dam site in karst depression area.