Abstract: To study the wetting deformation of rockfill materials， the effect of particle size on the strength and softening coefficient of rock particles was first analyzed by laboratory single-particle crushing tests. Then the stress-strain transformation relation between saturated and dry specimens was established by using stress and strain tensor expressions of granular aggregate and the softening coefficient of rock particles， and the wetting deformation of the rockfill materials was predicted using the double-line method. Finally， the effectiveness of the method was evaluated based on the example analysis. The results show that wetting reduces the strength of the rock particles， and the crushing strength of both saturated and dry basalt particles conforms to a Weibull distribution. The characteristic strength of the particles decreases with increasing particle size， although the Weibull modulus and the softening coefficient of the particles are minimally affected by particle size. The stress-strain relationship between saturated and dry specimens of rockfill materials can be converted by the softening coefficient of the particle. The wetting deformation caused by particle breakage can be estimated by the stress-strain relationship of the saturated specimen and the particle softening coefficient. The predicted results are consistent with the test results overall， indicating that particle breakage due to the reduction of particle strength after water immersion is the main reason for the wetting deformation of rockfill materials.

Key words: rockfill materials; wetting deformation; softening coefficient; particle crushing; stress-strain curve