Natural soils usually experience multiple drying and wetting cycles in geotechnical engineering. In this paper, the influences of history of drying and wetting upon the desorption and adsorption soil–water retention curve (SWRC) of silicon micro-powder (SMP) and Guangxi Guiping clay (GGC) are examined and discussed. The experimental results presented are obtained by using an improved pressure-plate instrument. The results show that the size of the hysteresis loops decreases with increasing drying–wetting cycles, and these are almost identical after 4 drying–wetting cycles. In addition, the all drying–wetting curves are best fitted by VGM model, and the estimated drying air-entry value reduces with the drying number and remains almost unchanged in the fourth and fifth drying. On the contrary, the wetting estimated air-entry value increases with the wetting number and tends to a stable value.

在土力工程中，天然土壤通常经历多次干燥和润湿循环。本文研究和讨论了干燥和润湿的历史对硅微粉（SMP）和广西桂平粘土（GGC）的解吸和吸附水土保持曲线（SWRC）的影响。提出的实验结果是通过使用改进的压板仪器获得的。结果表明，磁滞回线的大小随干湿循环的增加而减小，并且在经过4个干湿循环后，它们几乎相同。此外，所有的干湿曲线都最好通过VGM模型拟合，并且估计的干燥空气进入值随干燥次数而减少，在第四和第五次干燥中几乎保持不变。反之，