Critical stress and plastic deformation of graded aggregate material under long-term dynamic repeat load

A research was made of the graded aggregate base bitumen pavement to investigate the rule of plastic deformation and its distribution in different confining stresses and dynamic stresses by using the middle dynamic triaxial instrument and sample compacted by vibration. Test proves that when confining pressure is fixed, the graded aggregate material's plastic deformation curve is stabilization type, disintegration type and destroy type with the increasing of dynamic load, two critical state can be confirmed by plastic deformation distribution. Critical dynamic stress increases in linearity and dynamic stress ratio descends in logarithm with confining stress, two critical dynamic stress ratio tends to the same when confining pressure is high. The relationship between plastic deformation and critical dynamic stress is exponential, stabilization critical stress level and destroy critical stress is 0.79 and 1.0, respectively. The analysis of representative pavement structure indicates that graded aggregate transition base's critical stress level is from 0.72 to 0.92 in standard axial load, which is lower than the destroy critical stress level. The graded aggregate base plastic deformation is stabilization under long-term vehicle load.