## 4 Conclusions  
1. At low cementation solution concentrations, when CaCl\({}_{2}\):urea reaches 1:1, the amount of urea basically reaches the inhibition limit, and it is not economical to boost the ratio of urea. At high concentrations of cementation solution, the suitable ratio of CaCl\({}_{2}\):urea should be 1:1.5 for economic reasons. The process of EICP can be divided into three stages: an express reaction period, a weak period, and a stable period. The first stage of EICP can provide a higher urease activity than MICP, but it is easy to inhibit because of the lack of cell structure protection, and the calcium carbonate precipitation efficiency is reduced. The lower the cementation solution concentration is, the shorter the duration of the rapid reaction period and the earlier the reaction ends. An total of 41\(\sim\)68% of the whole reaction can be completed within the first 4 h of the reaction, and 87-98% can be accomplished in 24 h. When the cementation solution concentration is 1.6 M, the calcium carbonate precipitation ratio is the highest.
2. The optimal concentrations of skim milk powder, glutinous rice powder, and brown sugar are 8 g/L, 8 g/L, and 16 g/L, respectively. The strengthening effect of adding any one of the three organic materials alone is generally poor, and the strength is only increased from 6\(\sim\)52% compared to that of the untreated soil. The strength through the improved EICP method containing organic material is nearly 4 times higher than that of the original soil and 25\(\sim\)33% higher than that of traditional EICP. The improvement from skim milk powder is the best herein, followed by glutinous rice powder, and that with the brown sugar was the weakest. The modification effect difference is mainly due to the different template and matrix amounts of nucleation sites for calcium carbonate crystal formation.
3. The improvement effect of EICP combined with organic materials is not the simple superposition of the two alone. The incorporation of organic materials can promote calcium carbonate to continuously accumulate and stack to form new crystals with the constituents of organic materials as templates and nucleation sites, producing multiparticle cluster-shaped crystals, which can facilitate the transition of calcium carbonate crystals from vaterite to calcite and compensate for the lack of nucleation sites and low strengthening efficiency of fine-grained soil in traditional EICP.
4. Considering the difficulty of injecting the treatment solution into fine-grained soil, multiple injection cycles were not adopted. The treatment solution containing organic materials was mixed with silt in this study, and the total amount of reaction liquid was less. Compared with EICP, the CCC changes little (approximately 1%), the strength is increased by approximately 33%, and the strength enhancement efficiency is raised by 32% through modified-EICP treatment, which shows that the improvement of modified EICP is mainly attributed to an optimization in the calcium carbonate crystal structure. Soil reinforced by both EICP and improved EICP shows brittle failure. The greater the strength increases, the more obvious its brittle failure characteristics.  
Conceptualization, H.Y. and Z.Z.; methodology, G.R. and Z.Z.; software, W.Z.; validation, G.R., K.L., and W.Z.; formal analysis, H.Y. and G.R.; investigation, H.Y.; resources, Z.Z.; data curation, G.R. and K.L.; writing--original draft preparation, G.R.; writing--review and editing, H.Y. and Z.Z.; visualization, G.R.; supervision Z.Z.; project administration, Z.Z.; funding acquisition, Y.H. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Key Research and Development Project of Henan Province (Science and Technology Research Project) (Grant No. 202102310247). All authors thank the anonymous reviewers and the editor for the constructive comments on the earlier version of the manuscript.  
The authors declare no conflict of interest.