# Effects of Water-Soaking Height on the Deformation and Failure of Coal in Uniaxial Compression
## 4 Conclusions  
In this paper, laboratory tests were conducted to understand the effect of water-soaking height on the deformation and failure of coal in uniaxial compression. The main conclusions are:  
1. Water contents of coal specimens increase with the soaking height. Water significantly weakens the strength of coal specimens. The strength of nonsoaking coal specimens was the highest, and the strength of fully soaked coal specimens was the lowest. The strength of coal specimens with different water-soaking heights did not decrease with the increase of water content, and the unevenness of water distribution had a significant impact on the strength of coal specimens. Uneven distribution of moisture exacerbates deformation and damage of coal.
2. Acoustic emission activities of fully soaked coal specimens and nonsoaking coal specimens were relatively concentrated, occurring mainly in unstable fracture expansion stage and post-peak  
Figure 12: Evolution of axial stress and local strain difference for different soak heights specimens at different loading times. (**a**) 0 mm water-soaking height; (**b**) 25 mm water-soaking height; (**c**) 50 mm water-soaking height; (**d**) 75 mm water-soaking height; (**e**) 100 mm water-soaking height.  
destruction stage. Partially soaking coal specimens, especially the 25% water-soaking height coal specimens and 50% water-soaking height coal specimens, produced obvious acoustic emission activities during the fracture expansion stabilization stage, and then more acoustic emission activities were generated during the unstable expansion stage and the post-peak stage. The characteristics of acoustic emission showed that the heterogeneity of the partially soaking coal specimens was more obvious than that of the fully soaked coal specimens and nonsoaking coal specimens.
3. The nonuniform deformation index \(Si\) can reflect the nonuniform deformation characteristics of coal specimens with different water-soaking heights to some extent. The larger the \(Si\) value of the nonuniform deformation index, the greater the extent of nonuniform deformation of the coal specimens. According to the Si index, it was also shown that the nonuniform deformation of the 25% water-soaking height coal specimens was most obvious among all the coal specimens.  
[PERSON] carried out the experiments, analyzed the results, conducted the theoretical explanations, as well as wrote the manuscript. [PERSON] conceived and designed the framework. [PERSON] reviewed the technology concepts, assisted to analyze the AE data, and performed significant review and editing of the technical paper. [PERSON] provided some help about the mechanical analysis. [PERSON] guided the structure of the article. [PERSON] and [PERSON] assisted to conduct the experiments.  
This research was funded by the Joint Funds of the National Natural Science Foundation of China (U1710258), the National Natural Science Foundation of China, Young Scientists Fund (No. 51804209); Shanxi Applied Basic Research Programs, Science and Technology Foundation for Youths (No. 201801D221363); Shanxi Province Applied Basic Research Program (No. 201801D221342); Science and Technology Innovation Project of Shanxi Colleges and Universities (2019 LO181). Thanks for all the support for this basic research.  
The authors are very grateful to the editors and reviewers for their kind and invaluable comments.  
The authors declare no conflict of interest.