江口水电站排水孔涌水异常问题的分析

Analysis on abnormal gushing at the drain holes of Jiangkou hydropower station

江口大坝2007年6月20日发生两处排水孔涌水异常，一处为232高程左岸灌浆廊道与吊物井之间的两个排水孔，另一处为170高程二道坝廊道与右岸排水廊道交接处。事发时19～20日发生暴雨，初期大量涌水并伴有泥浆，但泥沙含量逐渐减少，降雨结束后30h还原至初始状态。通过综合分析，查明了排水孔涌水来自山体。涌水异常原因是防渗帷幕的形成、III-404夹层的置换处理、KW11（锣鼓洞）和K8-K12两个岩溶系统的封堵以及F35断层的存在阻断或改变了原有的地下水渗流途径，地下水不断的溶蚀作用使夹层溶洞的充填物带出，出现涌水异常。对涌水异常发生情况、涌水异常原因以及处理意见进行了阐述。

Abnormal gushing at two drainage holes of Jiangkou hydropower station occurred on June 20, 2007. One was the drainage hole between the grouting gallery at left bank and hoist shaft on the elevation 232 m, while another was at the junction part of the second dam gallery and the drainage gallery of right bank on the elevation 170 m. As heavy rain on June 19-20, abnormal gushing with mud from drainage holes was found in the beginning. Then, mud and sand in the gushing water decreased and returned to normal after 30 hours. By comprehensive analysis, the cause reason was concluded that the engineering treatment before changed the seepage path of underground water, as a result, the filling material in the cave was rushed out because of serious corrosion. The treatment measures included the formation of the impervious curtain, the replacement of 111-404 sandwich, the closure of KW11 and K58-K12 cave systems and the existence of F35 fault which blocked or changed the pathway of the original groundwater seepage. Accordingly, treatment advices were presented.