Abstract: The relationships between resilient modulus of improved expansive soil and wettingdrying cycle and dosage of weathered sand respectively were researched through testing the resilient modulus of expansive soil improved by weathered sand. The weak expansive soil in Yichang was taken as the research object. Results showed that 1) with the same dosage of weathered sand, the expansive soil’s resilient modulus gradually decreased with the increasing number of wettingdrying cycles. The decay rate reached maximum at the first wettingdrying cycle, and then gradually decreased. When the wettingdrying came to the fourth to fifth cycle, the resilient modulus is basically stable. Resilient modulus and wettingdrying cycle can be fitted with exponential function, and the correlation is quite well; 2) after the same wettingdrying cycles, the decay rate of resilient modulus and the amount of soil’s microcracks decreased with the increase of weathered sand dosage; 3) in consideration of the coupling effects of wettingdrying cycles and weathered sand dosage, the threedimensional nonlinear prediction model of weathered sand improved expansive soil’s resilient modulus under wettingdrying cycles was established. The prediction model is of simple form and high accuracy, hence it is worth promotion.

Key words: expansive soil, weathered sand, wettingdrying cycles, resilient modulus, prediction model