Joint back analysis of the creep deformation and wetting deformation parameters of soil used in the Guanyinyan composite dam

The inserted junction in the composite dam of the Guanyinyan hydropower station, with a height of 75 m, is the weak point of the dam structure. During the first impoundment, cracks appear on the junction crest of the earth-rockfill dam, which primarily results from the uncontrollable deformations of the dam. The deformations of earth-rockfill dams generally include static, rheological and wetting deformations. Therefore, the deformation parameters, which include the constitutive model, rheological and wetting parameters, are the key issues for controlling dam deformation. In this paper, parameters of the E-B model (constitutive model), creep deformation model and wetting model of the earth-rockfill materials were jointly back-analyzed using a parallel mutation particle swarm optimization method, according to the displacements that were monitored on the dam body. The back-analysis results showed that the non-uniform settlement induced by creep deformation and wetting deformation of the dam soil ultimately caused the cracks on the crest. More than 83% of the displacement that is generated by creep deformation is predicted to be released within three years after impoundment, and the total settlement on the crest ten years after construction is predicted to remain at less than 1% of the dam height.