对初始状态相同南阳膨胀土试样进行1～6次干湿循环，选取其中的1、3、6次循环后的试样，采用饱和盐溶液蒸汽平衡法测定其含水率、孔隙比、饱和度等与吸力的关系，并对比分析干湿循环对南阳膨胀土的持水能力影响。在1～6次干湿循环过程中，以环刀为参照物拍摄每次烘干后试样上表面照片，用数字图像处理提取图像中的裂隙与收缩面积，以此分析试样烘干过程中裂隙与收缩与干湿循环次数的关系。试验结果表明，干湿循环过程中相同吸力的试样含水率略降低、孔隙比略增大、持水能力略降低，烘干过程中试样收缩面积增大，裂隙展开面积增大，但上述性质变化幅度都随干湿循环次数增加而减小。试验成果为研究膨胀土的持水能力和湿胀干缩变形性质随干湿循环的变化规律提供实测数据。

The specimens of Nanyang expansive soil compacted at the same initial condition, were subjected to one to six wetting-drying cycles; and then the specimens after one, three and six wetting-drying cycles were selected for measuring the relationship between suction, water content, void ratio and saturation degree by the vapor equilibrium method using saturated salt solutions; and thus the soil-water characteristics of compacted Nanyang expansive soil was analyzed. When every drying process finished; the picture of the specimen top surface was taken. The pictures were dealt by the digital image processing using cutting ring as a frame of reference, and then the shrinkage and crack areas were extracted. The shrinkage and crack areas developing with drying-wetting circles were analyzed by calculating the ratios of shrinkage and crack areas to cutting ring area. The test results show that with the increasing of wetting-drying cycle, water content decreases, void ratio increases and water retention capacity decreases, and the shrinkage and crack areas after oven dry increase. But the changes in the above behavior become less with increasing the cycle. The above test results are useful to study soil-water and shrinkage characteristics of expansive soils during drying-wetting circles.