To determine the deformation characteristics of silt clay under long-term static loadings, small-sized plate loading creeping tests are performed using the element model with filling soil at compaction efforts of 0.90, 0.95 and 1.00m, respectively, through which the vertical settlement-time curves and rebound deformations under designed load levels are obtained. According to the concept of creep limit, long-term strength and relative instantaneous strength in the soil rheology, four categories including fast stability, long-term stability, long-term damage and rapidly damage are identified. Based on the attenuation characteristics that the soil creep rate shows a negative power function with the time, the fractal characteristic during convergence-type decay creep is revealed. To discriminate the category of deformation characteristics, a “power criterion” is proposed for quantitatively distinguishing soil deformation evolution state, based upon which three loading thresholds are determined by the small-sized plate loading creep tests. Combined with the feature that rebound deformation amount grows approximately linearly as load increases, three rebound strain thresholds for the four deformation evolution states are obtained. These results provide theoretical and experimental bases for determining the deformation evolution state of geotechnical structures.