## 4 Conclusions  
To study the strength characteristics of cast-in-situ shaft walls under slurry conditions, experiments were conducted on slurry formulation as well as mortar casting in three different environments: slurry, pure water, and dry conditions. The cast specimens were subjected to compressive, tensile, shear strength tests, and microscopic observations to understand the strength development patterns of mortar specimens in different casting environments. The main conclusions are as follows:  
1. Preliminary experiments identified a mortar formulation with suitable strength, good flowability, and underwater non-dispersion properties, as well as a drilling slurry with good stability, certain viscosity, and relative density. 2. Physical simulation experiments showed that as the casting environment becomes more complex, the strength of the cast specimens decreases gradually. Specimens cast in a slurry environment showed a strength reduction of approximately 15-20% compared to those cast in a dry environment, while the strength reduction in a pure water environment was less than 5%. 3. Despite different complexities in casting environments, the compressive, tensile, and shear strengths of the specimens exhibited a similar trend over curing time: the early-stage strength (1 to 7 days) increased rapidly, reaching over 80% of the 28 th-day strength, while the later-stage strength (7 to 28 days) increased more slowly. 4. Different casting environments significantly affected the pore structure of the specimens. Specimens cast in a dry environment had fewer, smaller, and more dispersed air voids. In pure water environments, the number, diameter, and density of air voids increased. In slurry environments, the air voids were the most concentrated and exhibited a bimodal distribution. In conclusion, despite some strength loss, specimens cast in slurry environments still possess relatively high tensile, compressive, and shear strengths. Building on these results, we plan to employ an integral lifting method to construct cast-in-situ model shaft walls and perform corresponding tests. This study provides data and theoretical support for the strength characteristics of cast-in-situ shaft walls under slurry conditions. In addition, the use of high-strength mortar as a substitute for concrete still has limitations due to the absence of coarse aggregates, and we will focus on extending the substitute mortar to actual concrete in the future research, including large-scale validation tests and long-term performance evaluations. Conceptualization, T.L. ; methodology, Z.Y. and T.L. ; validation, Y.C., C.J. and T.Z. ; formal analysis, Z.Y. and T.L. ; investigation, Y.C. and T.Z. ; resources, W.Y. ; data curation, Z.Y., Y.C. and T.H. ; writing--original draft preparation, Z.Y. and Y.C. ; writing--review and editing, T.L., T.H. and W.Y. ; visualization, T.H. ; supervision, T.L. ; project administration, W.Y. ; funding acquisition, W.Y. All authors have read and agreed to the published version of the manuscript. This study was supported by the National Natural Science Foundation of China (Grant No. 52074264, 41501075), the Fundamental Research Funds for the Central Universities (Grant No. 2021 GJZPY15), and the Foundation Research Project of Xuzhou (Grant No. KC22061). Not applicable. The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author. Author [PERSON] was employed by the company Shandong Energy Group Xibei Mining Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Not applicable. The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author. Author [PERSON] was employed by the company Shandong Energy Group Xibei Mining Co., Ltd.