Long-term deformation characteristics of high concrete-faced rockfill dams under cyclic loading of water

The long-term deformation of high concrete-faced rockfill dams is one of the key technical problems during their construction. Most studies have attributed the long-term deformation to rockfill creep, but the prototype monitoring data of some high concrete-faced rockfill dams show that it is difficult to explain the mechanism of their long-term deformation only from the viewpoint of rockfill creep. In this study, based on the analysis of the deformation monitoring data of Shuibuya concrete-faced rockfill dam for 17 years and the tests of the deformation characteristics of rockfill materials under low-frequency cyclic loading, the influences of cyclic loading caused by periodic change of reservoir water level on the long-term deformation characteristics of high concrete-faced rockfill dams are discussed. The results show that: (1) The instantaneous deformation and creep of rockfills body are caused by dam filling and initial water impoundment, and the post deformation of rockfill mainly results from the long-term action of cyclic loading of water. (2) When considering cycle loading of water, the deformation of rockfills exhibits two forms: one is the irrecoverable permanent deformation (also known as residual deformation), and the other is the recoverable elastic deformation. (3) The deformation of rockfills and its growth response obtained from the low-frequency cyclic load tests well verify the relationship between the cyclic loading of water and the post deformation of the rockfill dam as well as the mechanical significance of the later deformation. The research provides a new idea for the studies on the long-term deformation characteristics of high concrete-faced rockfill dams, and it also provides reference for the deformation and safety control of high concrete-faced rockfill dams with reciprocating characteristics.