Detection of hidden piping defects in dikes by transient electromagnetic technique

摘要

Geophysical Transient Electro-Magnetic Sounding (TEM) was employed in detection of hidden leakage defects in dikes, and Series SDC Dike Leakage Detector was developed by authors. TEM is a nondestructive detection technique (NDT). The advantages of TEM are that no electrode into ground, high resolution, high detection speed, easy to operate, and so on. The instrument can be applied not only in general survey of hidden defects and leakage in dikes and dams, but also in locating piping paths. The instrument was took part in the competitive testing of instruments held by National Office of Flooding Control and Fight Against Drought for detection of artificial hidden defects at an old dike of Yongding River in Beijing. Applications in site were conducted at three dikes in Yueyang County, Hunan Province, in 1999. Tests included detection of hidden leakage defects in dry season, and locating piping paths in flood season. The detection line was 17.4km long, and the detection depth was 30～60m. Five hidden piping defects had been found in Damaojiahu dike in dry season, where piping danger happened in flood season, and two new piping paths were found out in the same dike. The detection result in dry season was certified by watching piping path happened in flood season. It was also certified that TEM is an efficient method for detecting and locating hidden piping defects in dikes.