**4. Conclusions**

The optimum dosage and ratio of additives for amending compacted clay were screened and determined through moisture retention and gas diffusion test. The principal reason for the enhancement of its moisture retention capacity was investigated by the liquid–plastic limit test. Subsequently, the hydraulic performance of the compacted clay amended by additives and unamended was conducted. Based on the results, the following conclusions can be drawn:


**Author Contributions:** Conceptualization, M.W., J.W. and Y.D.; methodology, M.W., Y.D. and J.W.; software, M.W.; validation, M.W. and N.J.; formal analysis, M.W. and J.W.; investigation, M.W., J.W. and H.Z.; resources, M.W.; data curation, M.W. and J.W.; writing—original draft preparation, M.W., J.W., H.Z. and W.X.; writing—review and editing, M.W., Y.D., H.Z. and N.J.; visualization, M.W.; supervision, M.W., Y.D. and W.X.; project administration, Y.D.; funding acquisition, Y.D. All authors have read and agreed to the published version of the manuscript.

**Funding:** Financial support for this project was provided by the National Key R&D Program of China (Grant No. 2018YFC1803100), the National Natural Science Foundation of China (Grant Nos. 41877248, 42177133, and 41902276).

**Data Availability Statement:** Some or all data, models, or code that support the findings of this study are available from the corresponding author upon reasonable request.

**Conflicts of Interest:** The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
