Long- term operation and the influence of natural environment may lead to seepage

cracks and other defects on rockfill dam with inclined clay core

posing a threat to the stability of dam body. This paper proposes the joint application of opposing coils transient electromagnetic method (OCTEM) and ground- penetrating radar (GPR) to the safety evaluation of rockfill dams with inclined clay core

 and explores the effectiveness of these two methods in detecting the internal structure and potential defects of the dam. The research shows that OCTEM can effectively identify the internal blasting accumulation line of the dam body

and also can discover multiple seepage problems. The GPR can clearly show the interfaces between upstream panel layer

the sand layer and the clay layer

and identify problems such as insufficient compaction

surface voids and local settlement. The combined application of these two methods not only enables comprehensive detection of both the dam′s surface and internal structure but also compensates for their respective limitations

forming an effective detection system that provides reliable basis for dam safety evaluation.