A large amount of leakage occurred in a geomembrane rockfill dam after impoundment. After five treatments, the leakage still reached 632 L/s, relatively large among similar projects. The geophysical detection, underwater inspection and monitoring data are combined to analyze the possible leakage passages. The results show that there may be leakage passages in the anti-seepage curtain of lower grouting adit on the right bank of dam. The calculation results of the seepage stability of dam foundation show that some local seepage gradient in dam foundation is larger than the allowable seepage gradient. As safety hazards exist in the long-term dam operation, corresponding engineering measures should be taken to guarantee safe operation.

geomembrane rockfill dam, abnormal leakage, leakage passage, seepage stability

某土工膜堆石坝下闸蓄水后即出现较大渗漏量，经过5次处理后，渗漏量仍达632 L/s，在国内外同类工程中偏大。综合物探检测、水下检查和监测数据，对可能存在的渗漏通道进行分析，结果表明大坝右岸下层灌浆平洞防渗帷幕可能存在渗漏通道。对坝基渗透稳定性进行计算，结果表明坝基局部渗透坡降大于允许渗透坡降。大坝长期运行存在安全隐患，应采取相应工程处理措施，确保运行安全。

土工膜堆石坝, 渗漏异常, 渗漏通道, 渗透稳定性