江垭大坝基础排水孔管涌原因与处理

Piping from Foundation Drain Holes at Jiangya

江垭大坝于1998年10月18日下库蓄水。在初期运行过程中，8^#坝段基主排水孔发生突发性强涌水，携带出中、粗砂20余m^3,基础廊道被淹。积水抽干后，通过各项观测、孔内电视、水文地质条件和渗控工程布置特征等综合分析，查明了坝基主排水孔涌水来自左岸山体。管涌原因是防渗帷幕阻断了下部含水层的渗流排泄通道，两岸坝肩幕后山体排水未形成，无新的排泄出逸处，主排水孔未设反滤。暴雨期间排泄不畅，叶下水急骤升高，使坝基层间溶蚀带内的充填物产生渗透破坏，出现管涌。对管涌发生情况、管涌原因、处理步骤、完善排水设施、处理效果与体会作了全面阐述。

The reservoir impounding started at the Jiangya RCC dam on October 18, 1998. In the period of initial operation, a strong piping with more than 20 m 3 of median and course sand occurred from the primary drain holes in dam foundation and the foundation galleries were flooded. After unwatering out, by the analysis on data obtained by TV-in-hole, hydrological and geological conditions and engineering arrangement of leaking control, it has been ascertained that the piping water originated from the left mountainous body, resulting from no discharge passage of the underlying water bearing beds, no drains available for the mountainous body behind the curtain in both the abutments, no new draining exits, as well as no arrangements of inverse filter for the primary drain holes. Due to the blocked draining during rainstorm, the ground water level rose rapidly and disturbed further the fillers in the solution zones in foundation, finally resulting in the piping. The writer gives a detailed description of the occurrence, causes, treatment measures for improvement of the drainage and effect, as well as his understandings.