一、概述天桥电站土坝位于水寨岛右侧,坝顶长330米,坝高23米,为一宽土质心墙砂砾石碴混合坝。坝址处河床宽270米,河床标高812.0～814.0米。河床冲积层厚约20米,上部为中粗砂含砾层,厚14～17米,渗透系数 K=15～20米/日;下部为沙砾石层,厚3～7米,渗透系数 K=25～35米/日。河床基岩为 O_2~(12)角砾状灰岩,出露标高792.0～795.0米,系一天然相对隔水层,其隔水作用与层厚有直 I. Overview The Tianqiao Power Station earth dam is located on the right side of Shuizhai Island. The crest of the dam is 330 meters long and the dam height is 23 meters. It is a wide earth-gravel ballast mixed dam. Dam riverbed 270 meters wide, riverbed elevation 812.0 ~ 814.0 meters. The alluvial bed thickness of about 20 meters, the upper part of coarse sand gravel, thickness 14 to 17 meters, the permeability coefficient K = 15 ~ 20 m / day; the lower part of the gravel layer, thickness 3 to 7 meters, the permeability coefficient K = 25 ~ 35 m / day. The bedrock of the river bed is O_2 ~ (12) brecciated limestone with an elevation of 792.0 ~ 795.0 m, which is a natural relative aquitard whose water barrier and thickness are straight