Filled road embankment along river levee or widen river levee as road embankment is often used in highway construction, part of the embankment will always immerged in water for seepage. The intensity of the filler will decrease due to the long-term immersion，which lead to eventually failure, especially in the expansive areas. This paper carried out CBR test on the lime improved expansive soil after different time’s immersion. The test results show: The CBR will linearly decreased with the previous immersion time, and then, it varies very small with the immersion time, and the stable CBR after long term immersion is about 80% of the CBR under standard condition. The paper put forward a prediction model of CBR by the immersion time, it can be used to predict the CBR of improved expansive after long term immersion, and to judge whether it meet the requirements of specification.
