Mechanism of PVA hydrophobic cushion layer to prevent basal erosion in earthen sites: Three-dimensional model tests and numerical simulation studies

• Published in: Engineering geology 2023-09, Vol.323, p.107218, Article 107218
• Main Authors: Zhang, Qiyong, Chen, Wenwu, Zhang, Jingke
• Format: Article
• Language: English
• Subjects: Earthen site; Polyvinyl alcohol composite soil; Soluble salt; Water-salt migration; X-ray computed tomography
• ISSN: 0013-7952; 1872-6917
• DOI: 10.1016/j.enggeo.2023.107218

Water-salt migration is an important reason for the development of basal erosion which seriously threatens the conservation of earthen sites. Studies in cutting-off or redirection of the water-salt migration path become vital. Polyvinyl alcohol (PVA) composite soil with extreme hydrophobicity shows the potential as the cushion layer with the damp-proof function, but the feasibility of preventing basal erosion based on the PVA cushion layer still lacks verification. In this study, for the embedded and non-embedded PVA cushion layers, water-salt distribution and morphology of earthen wall after repeated injection of salt solution were compared. The results showed that PVA cushion layer changed the water-salt migration path and promoted the accumulation of soluble salt on the ground outside the wall rather than the bottom of cushion layer, which effectively prevented basal erosion. A numerical model based on HYDRUS-2D confirmed that a partial laying of hydrophobic cushion layer under the wall cannot effectively prevent the water-salt migration, and a full laying of cushion layer should be adopted to prevent basal erosion. The cushion layer was recommended to extend towards the direction of the earthen wall instead of towards the sides, which also resisted the destructive effects of sand-driving wind and runoff erosion. •Basal erosion caused by water-salt migration is directly confirmed.•Water-salt distribution for models with/without PVA cushion layer is explored.•PVA cushion layer can inhibit basal erosion.•Reasonable laying modes of the hydrophobic cushion layer is presented.