## 4 Conclusions  
This paper proposed a new method by which to evaluate the homogeneity and structure of remolded loess samples based on the air permeability coefficient. The conclusions are as follows:  
1. When the moisture content is fixed, the delamination dry density of remolded samples changes with the designed dry density and the overall height of the sample.
2. With the increase in sample height, the air permeability coefficient of the sample gradually increases, which indicates that the sample tends to be more uniform with the increase in the overall sample height. The more uniform the soil sample, the greater the air permeability coefficient of the remolded sample.
3. When the dry density was \(\rho_{d}<1.58\) g/cm\({}^{3}\), the air permeability and structural texture index \(m_{k}\) of remolded loess were found to first decrease and then increase with the increase in moisture content; when \(\rho_{d}\geq 1.58\) g/cm\({}^{3}\), \(m_{k}\) was found to increase with the increase in the moisture content of remolded loess, and the range of the increase in \(m_{k}\) was found to vary with dry density.
4. Combined with the microscopic scanning electron microscope images, it was revealed that the redistribution of clay, colloidal particles, and soluble salt ions in undisturbed loess during countless drying/wetting cycles endows the loess with a strong structure. However, remolded loess is characterized by the greatly reduced effectiveness of cementation between skeleton particles, which causes its structure to be weaker than that of undisturbed loess.  
In summary, the air permeability coefficient is demonstrated to be a powerful tool in evaluating the homogeneity and structure of remolded loess samples, with good application prospects. However, compared with the visual damage of the water permeability test, there are still many variables that cannot be controlled independently. For example, since the undisturbed loess has a more open pore structure, the results of the air permeability test are related to the number and connectivity of effective pores in the soil. This test may therefore have certain limitations in determining microstructure information using macrophysical indicators. This will require us to introduce other influencing factors in future research for in-depth analysis and verification.  
Figure 15: The conceptual model of the (**a**) filling and (**b**) adsorption effects of colloidal clay.  
**Author Contributions:** Conceptualization, Z.H. and X.L.; methodology, Z.H., X.L., J.Z. and B.Z.; software, M.A., F.W. and B.Z.; validation, X.L. and F.W.; formal analysis, Z.H. and R.G.; investigation, Z.H., R.G., M.A., J.Z., F.W. and Q.X.; resources, X.L. and J.Z.; data curation, Z.H., R.G., M.A. and Q.X.; writing--original draft preparation, Z.H. and Q.X.; writing--review and editing, Z.H.; visualization, F.W. and Q.X.; supervision, X.L. and B.Z.; project administration, X.L. and B.Z.; funding acquisition, X.L. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China, grant number 41572264, and the National Natural Science Foundation of China, grant number 41877225.  
**Data Availability Statement:** Not applicable.  
The authors would like to sincerely thank the editors as well as the reviewers of this paper, who put forward useful comments that improved the manuscript substantially.  
The authors declare no conflict of interest.