## 7 Conclusions  
This paper successfully developed a novel paste filling material based on mountain sand by conducting a compositional analysis of mountain sand and fly ash, along with a numerical simulation analysis of filling in the corners of the working face. Additionally, this study investigated the distribution characteristics of the oxidation zone in the goat during the process. As a result, the use of inorganic paste filling at the corners of the working face was proposed and effectively implemented in underground field operations. The following conclusions were drawn:  
1. Through experiments involving the determination of particle size distribution and X-ray diffraction on commonly used filling aggregates, such as mountain sand and fly ash, it has been observed that mountain sand is an effective filling aggregate, while fly ash can be used as a substitute for cement as a filling auxiliary material. Based on this discovery, a new mountain sand-based paste filling material was developed. Through rigorous flowability tests, quick-setting tests, and expansibility tests, the optimal mass ratio for this new mountain sand-based paste filling material was determined to be 1:4:15 (cement: fly ash: mountain sand), with a solid concentration of 84%. Additionally, it is recommended to use a 9% dosage of a 85 quick-setting agent and a 0.5% dosage of a UEA expansion agent for optimal results. 2. Various corner-filling scenarios were simulated and analyzed for the 22,122 working faces using FLUENT 2022 R1 numerical simulation software. It was observed that filling significantly impacted the pressure field within the goat area. The presence of filling material in the upper corner reduced the pressure difference between the deep goat area and the lower corner, effectively mitigating air leakage at its source. Similarly, the presence of filling material in the lower corner decreased the pressure difference between the deep goat area and the upper corner, impeding the flow of harmful gases back to the working face and reducing the likelihood of gas exceeding safety limits in the upper corner. Overall, these findings contribute to the prevention of gas accidents by minimizing the risk of gas accumulation in the working face. 3. By employing FLUENT numerical simulation software, different interval distances for filling in the two corners of the 22,122 working face were examined. The findings indicate that the width of the oxidation zone within the goat area was impacted by the interval distance, displaying a trend of an initial reduction followed by an increase. The minimum extent of the oxidation zone within the goat area was observed at an interval distance of 50 m. It was determined that implementing a secondary filling in the corners of the working face was more effective in controlling the width of the oxidation zone within the goat area. However, it is essential to avoid excessively large interval distances. 4. The technology of inorganic paste filling was successfully implemented at the two corners of the 22,122 working face. After conducting two fillings with a 50 m interval between the upper and lower corners, the air leakage in the goat area decreased by 66.7% compared to unfilled conditions. Moreover, the width of the oxidation zone on the intake side of the goat area was reduced by 42%, while on the return side, it decreased by 33%. The filling material effectively acted as a barrier, preventing oxygen from entering the goat area and reducing the risk of spontaneous combustion of residual coal. This advancement significantly contributes to the safe extraction of the working face. **Author Contributions:** Conceptualization, L.S. ; Methodology, L.S. ; Software, L.S. ; Investigation, Z.X. ; Resources, Y.C. ; Data curation, L.T. ; Writing - original draft, L.S. ; Project administration, X.Z. ; Funding acquisition, C.L. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was funded by National Natural Science Foundation of China (NSFC): 52374140.