Study on Dynamic Parameters and Energy Dissipation Characteristics of Coal Samples under Dynamic Load and Temperature
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis study is of scientific and practical interest for the study of geodynamic phenomena in coal mines. recommended for printing.
1. The research examines the reaction of a carbon-bearing array under stress-strain conditions, to acting dynamic loads taking into account energy dissipation and the macroscopic reaction of coal.
2. This work is original, taking into account the fact that the energy acting on the coal sample is considered, taking into account the imposition of reflected energy on it leading to the formation of a dynamic system of internal cracks that are associated with the hardening of the sample.
3. The relationship of dynamic and static loads on a sample of coal representing micro and nanostructures, the regularity of energy dissipation depending on the voltage generated is established. These factors have been studied in relation to the temperature effect. The development of cracks consistent in the direction with the propagation of the stress wave will serve as a significant contribution to the practice of hydraulic fracturing of the coal seam, with the aim of its degassing and unloading in areas of increased stress-strain state of the coal seam.
4. The studies on the samples were performed correctly. It should be recommended that their results be transferred to the coal seam under stress-strain conditions and temperatures.
5. The results of the study are fully consistent with the conclusions presented in the conclusion, and the latter meet the purpose of this work – to study violations of the structure of internal pores and the propagation of cracks in the coal in its natural state (SSC and temperature) at abnormal values of the supply, reflected and scattered energy.
6. The recommendations set out in the conclusion are justified by experimental studies and correspond to the basic laws of energy distribution in coal and the physical effects that change the structure of coal, which is important for understanding the process of sudden emissions of coal and gas in mines.
7. To establish the connection of the results of research on coal samples with the coal mass in the formation, taking into account the rock pressure, the distribution of elastic energy under the action of mining mechanisms.
8. The references given correspond to fragments of articles.
9. The figures and tables are consistent with the text of the work. Table 3 should show the standard error of the estimation of the parameter being determined by the correlation level, as well as the number of observations used to obtain the level. Here, replace the correlation coefficient (for linear equations) with correlation relations (for polygonal ones), and also take into account that R2 is the correlation coefficient, since R 
R2, the sign of the correlation coefficient is not specified here. R2 - shows the proportion of closely related parameters of the argument and function, this is the coefficient of determination.
Comments for author File: 
Comments.pdf
Author Response
Thank you very much for your suggestions on the revision of this article.
In response to your 9th comment, we have carefully analyzed your definitions of correlation coefficient and determination coefficient. We have recalculated the values of the relevant parameter R in Table 3 and added the standard error between the number of observed samples and the fitting results.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors' article is devoted to an important and topical issue related to the study of the analysis of dynamic parameters and energy dissipation characteristics of coal samples.
The process in which a brittle collapse of a stressed structure of a seam in contact directly with a coal mine occurs is called a rock burst. It arises as a result of the conversion of potential energy inside a coal mass (the source of a rock burst) into kinetic energy. This is usually associated with abundant emissions of coal, ore, salt and other hard rocks, their collapse, strong sound vibrations and the formation of a shock wave. During these processes, a dynamic uneven redistribution of rock pressure occurs, which is a direct threat to serious accidents. They can result from weakening and destruction of support, as well as dangerous movement of mining and auxiliary equipment. The rock filling the mine workings affects the functioning of the ventilation system. It is disrupted, resulting in dangerous flammable gases accumulating in the voids.
In order for activities at mine sites to be safe from the point of view of the occurrence of rock bursts, it is necessary to carry out a set of preventive measures: reducing the tension of the coal seam by mining rock masses that are less susceptible to outbursts (advanced mining); formation of protective zones by reducing the risk of rock bursts in the bottom-hole part of the formation; technological orderliness of preparation and processing of arrays.
The forecast of outburst hazard in the faces of development workings in coal seams prone (threatened and dangerous) to coal and gas outbursts is carried out based on the structure of the coal seam, which is determined by the strength of the coal and by the results of measuring the initial rate of gas release from wells drilled through potentially dangerous units of the coal seam.
At the working face, the forecast is carried out using the same method in areas of a potentially dangerous coal seam, which are determined based on the results of geophysical studies in the excavation column prepared for mining.
Based on the relevance of the presented work, the results obtained in it will be useful for the analysis of specialists in this field.
However, there are the following issues that should be clarified:
1. The introduction should expand the literature review by comprehensively considering the various causes of rock bursts and the hazards that may occur when working in coal mines, in particular methane explosions, aerological risks, etc. In particular, one could pay attention to the practical results obtained in the following work https://doi.org/10.1016/j.ssci.2023.106170.
2. Should it be explained in more detail why dynamic experiments with coal were carried out at a temperature of 60 °C, and not at another temperature value? Are there plans to conduct experiments with other values of the parameters under consideration and a corresponding comparative analysis?
3. Are there plans to obtain a patent for the experimental system presented in Figure 1? It is necessary to dwell in more detail on its advantages compared to other known analogues.
4. Was a comparative analysis of the coal samples under consideration carried out in section “2.2. Coal Sample Preparation" with similar samples in other regions of the world? It would be possible to provide a more detailed description of the Hengda coal mine in question.
5. It was possible to conduct a correlation analysis between the values of the parameters presented in Figure 3.
6. Using the obtained regression equations shown in Table 3, it would be possible to obtain predicted values of output parameters for short-term and long-term periods of time. For these purposes, in recent years, forecasting methods based on machine learning, in particular using artificial neural networks, have become increasingly used (https://doi.org/10.3390/en15238919).
7. In section “4.2. Energy dissipation model” should explain in more detail what methods are used to determine the propagation of internal cracks in coal at the nanoscale.
8. The quality of the numerical values shown in Figure 7 should be improved.
9. It is necessary to add a “Discussion” section.
10. In the “Conclusions” section, specific objects on which it is planned to test the results obtained in the work and prospects for further research should be given.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for Authors1. Figures 1 and 2 should be separated by a, b and the caption of each should be written separately.
2. What is the importance of the subject being studied? Where are the results used? In particular, what will be the use of examining the effect of temperature on dynamic strength? This matter should be addressed in the introduction.
3. The tolerance of density and wave speed is high in the samples according to Table 1. If all the samples were from the same place, why is there such a difference in the values? It is good to specify the standard deviation of the values.
4. What does this sentence mean? “the coal samples show a certain degree of discreteness”
5. Explain why the strain changes are wavy in Figure 4? Does it mean that with the increase in temperature, it first decreased, then increased and decreased again? The results should be interpreted correctly.
6. Non-linear regressions in Table 3, with what software or method was done? And how is R2 obtained? Explain.
7. In the first equation of Table 3, the third sentence, the letter T is written in small letters. Please correct.
8. What is the reference of relationship 1?
9. Why in Figure 5-f, the energy changes are first decreasing, then increasing and then decreasing again? Interpretation of graphs should be added to the article.
Comments on the Quality of English LanguageMinor editing of English language required
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors revised the article and took my comments into account. The article may be published in my opinion.
Reviewer 3 Report
Comments and Suggestions for Authorsthere is no comment.
