Research and practice on piping treatment under change of embankment operation conditions: case of Lijiazhou section of Yaodi embankment along Hanjiang River

Piping is one of the most common and harmful dangerous situations in embankments.Its formation is complex and diverse, and the dangerous section of embankment piping can be effectively controlled after many times of danger removal and reinforcement.However, with the change of embankment operation conditions, new dangerous situations may still occur, which brings some difficulties to the treatment.In order to further study the treatment measures of piping danger, taking the first-class embankment in the Changjiang River Basin, Lijiazhou section of Yaodi embankment along Hanjiang River as an example, by collecting the historical dangers and geological data of the dangerous section, combining with the current situation of the built water conservancy projects, the causes of piping dangers in this section after danger removal and reinforcement were analyzed in detail.The distribution characteristics of the seepage field in the embankment section under various working conditions were revealed by the calculation of 3D seepage finite element model.Then the comprehensive treatment measures combining horizontal anti-seepage and drainage decompression were put forward, and a new type of removable relief well structure was selected and implemented under the hydrogeological conditions of the Xinlong Reservoir area.The treatment scheme had been implemented before the flood season in 2022,achieving the expected remediation effect.At present, Cuijiaying, Yakou, Nianpanshan, Xinglong and other cascade reservoirs have been built and under construction in the middle and lower reaches of the Hanjiang River, so the operation conditions of some embankments have changed from short-term water retaining in flood season to long-term medium and high head operation.The research results can provide references for the reinforcement and operation-maintenance of similar embankment projects under influences of reservoirs' operation.