## 5 Conclusions  
The ADNB polymer was a suitable choice as a soil stabilizer due to its special characteristics, such as uniform nanoscale particles when dispersed in water, which permitted the polymer to penetrate  
Figure 11: SEM image of the interior of the aggregates.  
Figure 12: Illustration of the mechanism of water stability of the aggregates: (**a**) inner expansion pressure generated; (**b**) stabilized shell ruptured by the inner expansion pressure.  
into the very small pores of soil, and suitable cohesive properties, which permitted it to play a better role in bonding soil particles together. To understand the penetration process of the soil stabilizer and the stabilization mechanism, laboratory trials of infiltration tests and water stability tests were performed. The mode of infiltration of ADNB in the soil as well as the stabilization of soil were proposed. The mechanism of water stability was analysed based on SEM images. The main conclusions can be summarized as follows:  
(a) The ADNB polymer emulsion had the characteristics of easy adhesion to soil particles, poor fluidity and large molecular volume. The effective infiltration depth of soil reached a maximum for samples treated with 2% ADNB and decreased when the concentration of ADNB increased.  
(b) The water stability of aggregates was significantly ameliorated by the ADNB treatment, which generated a protective shell with a particle-polymer matrix after evaporation of the water in the solution.  
(c) Aggregates with an average diameter of 15 mm exhibited an improved water stability over those with an average diameter of 7.5 mm when treated with the same concentration of polymer emulsion. This result could be explained by the fact that larger aggregates had smaller specific surface areas, on which there were larger amounts of effective polymeric emulsions than on aggregates with smaller diameters.  
(d) Based on the SEM results, two ways for ADNB to stabilize particles were observed: formation of a membrane structure on the surface and chain bonding inside. The latter had a weak bonding effect. The membrane structure that coated the soil particles and/or filled the pores via bonding was believed to play the main role in generating water stability.  
(e) The higher the concentration of the polymer emulsion was, the larger the thickness of the polymer membranes and the higher the water stability of the aggregates. However, the most economical and effective concentration for engineering applications was 2% ADNB.  
When ADNB is sprayed on a slope, the protective shell on the soil surface and large aggregates in the subsoil can not only prevent the loss of topsoil but also increase the number of pores of the soil interior, thereby enhancing the permeability of water and air in the soil, which is very important to the growth of plant roots in soil. Furthermore, because the final degradation products (CO\({}_{2}\) and H\({}_{2}\)O) do not pollute the environment, the application of ADNB can achieve the purpose of the ecological protection of the topsoil of clayey slopes.  
Conceptualization, C.Z. and Z.L.; Data curation, C.Z., S.Z. and Z.L.; Formal analysis, S.Z., W.H., D.L. and Z.L.; Funding acquisition, C.Z. and Z.L.; Investigation, S.Z. and Z.L.; Methodology, C.Z. and Z.L.; Project administration, C.Z. and Z.L.; Resources, C.Z. and Z.L.; Software, S.Z., W.H. and D.L.; Supervision, C.Z. and Z.L.; Validation, C.Z., Z.L. and S.Z.; Visualization, Z.L.; Writing--original draft, C.Z., S.Z. and Z.L.; Writing--review & editing, C.Z., S.Z. and Z.L.  
This research was supported by the Major Programs Special Funds of Applied Science and Technology Research and Development of Guangdong Province (No. 2015B090925016), the National Key Research and Development Project of China (No. 2017 YFC1501201) and the National Key Research and Development Project of China (No. 2017 YFC0804605).  
The authors declare no conflict of interest.