## 4 Conclusions  
In this study, the rules governing the mechanical properties of coal-cement grouts with different degrees of early damage under uniaxial compression were investigated. Using DIC and AE technology, the deformation and fracture characteristics of the samples were revealed from both internal and external perspectives. Furthermore, the microstructure of the fracture surfaces of the coal-cement grouts was investigated using SEM tests. Our conclusions can be summarized as follows:  
1. The resistance to pressure and elasticity of cluster modules with the increase in early damage has a decreasing trend, with the 40% highest resistance of early cluster coal-cement at 10.66 MPa, an increase of 24.38% compared to the resistance without clustering, while the strength of the cluster decreases to 8.16 MPa when the rise in early clustering is 60%. Therefore, early damage near the work surface to the strength of the coal-cement sample not only has a deteriorating effect; a certain extent of early disruption can increase the strength.
2. In the case of minor early damage, the surface rupture of the rock body is dominated by the damage of the strap, which increases with disruption, and the surface damage gradually turns to cutting and mixing destruction. The elastic phase microcracks begin to expand, and the cracks quickly expand on both ends after reaching the cracking stress, failing at an extreme load. The speed of the test partition increased with the early damage.
3. Internal fissure expansion mainly occurs in the sample destruction stage. As the disturbance increases the extension of the destruction phase, the cluster exhibits certain plastic characteristics, and a typical fragile destruction pattern occurs when the early damage increases to 60%.
4. The microstructure of the fissure surface shows that the early small disturbance is conducive to the penetration of slurry into the cracks of the coal, enhancing the effect of the grout reinforcement. The early major damage (60%) destroys the primary cluster, ultimately destroying the internal structure of the coal-grout rock, which leads to the deterioration of strength.  
The results indicate that in coal mine surface injection, the choice of appropriate injection time and adjacent work surface extraction speed can not only shorten the construction period and improve the efficiency of work but may also increase the strength of coal-burial rock in the pre-injection area, which is conducive to safer extraction.  
**Author Contributions:** Conceptualization, A.J.; methodology, H.D.; software, Y.Z.; validation, Z.W.; formal analysis, H.L.; investigation, H.L.; resources, H.D.; data curation, Y.Z.; writing--original draft preparation, A.J.; writing--review and editing, H.D.; visualization, Y.Z.; supervision, Z.W. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by [National Nature Science Foundation of China] grant number [52174106]. And [National Key Research and Development Program] grant number [2022 YFC2905102].  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data is contained within the article.  
**Conflicts of Interest:** Author [PERSON] was employed by Shanxi Jinmei Group Technology Research Institute 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.