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Earthen sites have important historical, cultural, artistic, social, and scientific values. However, they have been seriously destroyed by weathering. The methods of in situ replacement and sacrificial layer were previously presented to protect the surface of the earthen sites. This work presents the feasibility of the polyvinyl alcohol (PVA)-treated soil in a mud state as the anti-weathering material for these two methods. The desiccation cracking behaviour of soil was the main concern, and the surface peeling, hardness, and colour difference were used as the auxiliary evaluation criteria. The results showed that the PVA solution with a high degree of alcoholysis effectively inhibited soil cracking, but cannot eliminate all cracks even if the content reached 1%. The cracks of samples with the PVA mainly developed when the water content exceeded water content corresponding to air-entry value. Filamentous (or meshy) connections and cementation between particles were the main reason to inhibit the development of the cracks. The obvious advantages of the PVA in the decohesion index, hardness, colour difference, and so on cannot be also ignored. Based on these evaluation indicators, a PVA content of 0.8% may be the best choice for anti-weathering of earthen sites. [ABSTRACT FROM AUTHOR]

Earthen sites with important historical, cultural, artistic, social, and scientific values have been seriously damaged. Basal erosion, which is caused by soluble salts, water runoff, and sand-driving wind, is an extremely threatening erosion pattern for earthen sites. A cushion layer which has a damp-proofing function and good physical and mechanical properties can effectively decrease basal erosion. The primary aim of this study is to investigate material selection for the hydrophobic cushion layer for earthen sites in northwest China. The results indicate that cooked tung oil and sticky rice liquid, traditionally used in China, cannot meet the fundamental requirements of sufficient hydrophobicity for the cushion layer. Although polyvinyl alcohol (PVA) solution and tung oil exhibit similar properties in terms of soil hydrophobicity, water vapour permeability, water resistance, surface hardness, and colour difference for samples with 0.0-1.0% content, the PVA solution is significantly better than tung oil in unconfined compressive strength, deformation modulus, wave velocity, and viscosity. Therefore, the PVA solution should be preferentially selected as a hydrophobic cushion layer material according to the results of this work. When the mixing method is adopted, 0.6-1.0% PVA content is the best choice. [ABSTRACT FROM AUTHOR]