## 4 Conclusions  
This study investigated the application of MICP technology in soil surface cementation curing. The viscosity of the reaction solution was increased by adding HPMC, a cohesive material, and a series of tests, including mechanical properties, rainfall erosion resistance, wind erosion resistance, ammonia retention, XRD, and SEM, were performed on each test group using four reactant dosage gradients and three solution injection rounds. The results of the study showed that the MICP technique incorporating HPMC is effective for soil surface improvement.  
1. The content of CaCO\({}_{3}\) in the curst of the sample induced by MICP treatment increased with an increase in the number of treatments, and the addition of HPMC can effectively improve the content of CaCO\({}_{3}\) in the curst of the sample. MICP treatment with HPMC can produce up to 1.82 times as much calcium carbonate in the crust as MICP treatment alone, but has no effect on the total calcium carbonate. In addition, the incorporation of HPMC did not significantly change the formation of primary crystal type calcite.  
Figure 14: SEM image without HPMC addition.  
Figure 15: SEM image when adding HPMC.  
2. The rainfall erosion resistance of the soil surface layer was enhanced by the addition of HPMC combined with MICP technology. Rainfall losses were reduced by up to 30% in specimens treated with this method.
3. HPMC combined with MICP technology enhanced the wind erosion resistance of the surface layer. When the wind speed was 12 m/s, the maximum mass loss rate of the specimens treated with HPMC for MICP was only 0.828%.
4. The addition of HPMC and the increase in treatment cycles can effectively improve the surface strength of the sample. By adding HPMC and multiple treatments, more calcium carbonate precipitated in the surface layer of the sample. SEM images showed that more CaCO\({}_{3}\) filled the pores between soil particles and cohesive soil particles, forming a dense structure. The surface strength of the sample treated with HPMC was 1.61 times that of those without HPMC.
5. The ammonia retention rate of MICP treated with HPMC was significantly higher than that without HPMC. The ammonia retention rate of adding HPMC was 1.98 times that of not adding HPMC, which could effectively reduce the release of ammonia gas in the process of MICP, which is of great significance to environmental protection.  
Conceptualization, F.H., Y.Z. and Z.X.; data curation, M.Y.; formal analysis, M.Y., F.H., Y.Z. and Z.X.; funding acquisition, W.Z., F.H., F.M. and Q.T.; investigation, W.Z.; methodology, W.Z. and M.Y.; project administration, W.Z. and F.H.; resources, W.Z. and F.H.; software, M.Y., Y.Z., Z.X., Q.W. and F.M.; supervision, W.Z., F.H. and Y.Z.; validation, W.Z., F.H. and Y.Z.; writing--original draft, W.Z. and M.Y.; writing--review and editing, M.Y. All authors have read and agreed to the published version of the manuscript.  
The research was supported by the Postdoctoral Science Foundation of China (No. 2018M640683), the Postdoctoral Research Grant of Henan (No. 001801006), the National Natural Science Foundation of China (52078317), the Natural Science Foundation of Jiangsu Province for Excellent Young Scholars (BK20211597), the Bureau of Housing and Urban-Rural Development of Suzhou (2021-25; 2021 ZD02; 2021 ZD30), the Bureau of Geology and Mineral Exploration of Jiangsu (2021 KY06), and the China Tiesjiu Civil Engineering Group (2021-19).  
Not applicable.  
The authors declare no conflict of interest.