Earthen sites have important social, historical, artistic, and scientific value. Basal erosion, which is closely related to soluble salt, is one of the most important reasons for the destruction of earthen sites. Soil hydrophobicity may change the path of water–salt migration. Thus, it can protect earthen sites by inhibiting basal erosion at the bottom of earthen walls. However, the changes in the hydrophobicity after freeze–thaw and dry–wet cycles are still unclear. Therefore, the primary aim of this study is to investigate the effects of these cycles on the hydrophobicity of PVA composite soil with a high alcoholysis degree. The results indicate that soil hydrophobicity decreased with increasing number of freeze–thaw and dry–wet cycles. At a dry temperature of 80 °C, the soil lost its hydrophobicity. The surface hydrophobicity of immersed samples dried at room temperature decreased or was lost; however, the hydrophobicity inside samples still remained after five dry–wet cycles. Furthermore, an indicator based on the water inlet velocity was presented to judge the interior wettability. The changes in the wettability of the PVA composite soil were mainly controlled by changes in hydrogen bonds, the coiling and stretching of alkyl chains, and the orientation of free hydroxyl groups.

土遗址具有重要的社会，历史，艺术和科学价值。与可溶性盐密切相关的基础侵蚀是破坏土层的最重要原因之一。土壤疏水性可能会改变水盐迁移的路径。因此，它可以通过抑制土壁底部的基础侵蚀来保护土点。但是，冻融和干湿循环后疏水性的变化仍然不清楚。因此，本研究的主要目的是研究这些循环对高醇解度的PVA复合土壤疏水性的影响。结果表明，随着冻融和干湿循环次数的增加，土壤疏水性降低。在80°C的干燥温度下，土壤失去了疏水性。在室温下干燥的浸没样品的表面疏水性降低或消失；但是，经过五个干湿循环后，样品内部的疏水性仍然保持。此外，提出了一种基于进水速度的指标来判断内部润湿性。PVA复合土的润湿性变化主要受氢键变化，烷基链的卷曲和拉伸以及游离羟基的取向控制。