The wetting deformation of coarse-grained soil is of great importance to deformation and stability of earth-rockfill dam. CT triaxial wetting test was conducted to study the micro deformation mechanism of coarse-grained soil. The test result shows that the particle is softened and lubricated when water immerses the dry and stable soil under a certain axial stress condi-tion. The particle contact status changes from stable status to an unstable status, during which the particle continuously generates dislocation and movement until every single particle has a relatively large contact area. The final result of particle adjustment is that the porosity reduces and vertical deformation increases. Due to the strength reduction by softening and lubricating effect is greater than the strength gain by compacting effect, the strength of coarse-grained soil decreases after wetting, thus exerting un-favorable effect on dam safety.%粗粒土的湿化变形对土石坝的变形和稳定具有重要影响，通过粗粒土CT三轴湿化变形试验对粗粒土的细观变形机理进行了初步探讨。试验结果表明，对于处于某一轴向应力条件下相对稳定且干燥的粗粒土，由于水的浸润作用，颗粒被软化或润滑，原本相对稳定的接触状态变的不稳定，颗粒产生错动和转动，颗粒位置发生调整，直到各个颗粒具有相对较大的接触面积时重新趋于稳定状态。颗粒调整的最终结果是孔隙减小，竖向变形增大。由于颗粒软化和润滑作用导致的强度降低大于颗粒挤密作用带来的强度提高，因此湿化后粗粒土的强度降低，这会对坝体安全带来不利影响。
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