Numerical Investigation into the Mechanical Behaviours and Energy Characteristics of Hard Coal Subjected to Coupled Static-Dynamic Loads
Round 1
Reviewer 1 Report
REVIEWER REPORT
Numerical Study on the Mechanical Behaviours of Coal Subjected to Coupled Static-dynamic Loads
Type: Research Paper
I. The paper quality
1. Is the work understandable, correct, and appropriate for the journal? YES
2. Are they clearly stated? YES
3. Is the purpose or goal of the work within the journal’s scope? YES
4. Is the work correct and free of obvious errors? YES/NO
5. Are the methods and techniques employed appropriate? YES
6. Is the mathematics correct? YES
7. Is the work original and interesting? YES/NO
8. Is the work original and does it contain new results that significantly advance the research field? YES/NO
9. Have any parts of the paper already been published or considered for other publication? NO/YES
10. Is this paper likely to be cited in the future? May be
11. Is the paper scientifically sound and not misleading? YES
12. Does it provide sufficient information and in-depth discussion? NO
13. Is the presentation complete for a scientific paper? YES
14. Is there any critical information missing? YES
15. Is the presentation satisfactory? NO
16. Is the paper well written enough for evaluation of technical content? YES
17. Does the title reflect the contents of the paper? NO
18. Does the abstract describe the essential information in the work? NO
19. Does the introductory section adequately explain the framework and problems of the research? NO
20. Are the importance and usefulness of this research work clear? NO
21. Are sufficient references cited for providing a background to the research? NO
22. Is the length and format of the paper appropriate? YES
23. Is the conclusion logically supported by the obtained results? YES
24. Are the figures and tables easily readable, correct and informative? YES
25. Is the English understandable? YES/NO
26. Is the paper free of typographical and grammatical errors? YES
II. Recommendations (Minor revision)
I reviewed the above-mentioned manuscript for possible publication in APPLIED SCIENCES (ISSN 2076-3417).
The presented work presents a number of novel insights and solid scientific findings that can be viewed as a start point for upcoming, more in-depth studies.
All Minor revision are reported in the attache marked pdf file
Some small changes must be made to the submitted paper in order to improve it:
The research novelty in the introduction section has to be clarified,
-the references section needs to be updated.
-A separated discussion section can be added in order to compare obtained results with those from earlier literature studies such as
-Cheng et al Experimental Study on the Mechanical Behavior of Coal under Triaxial Dynamic Compression. Minerals 2022, 12, 1206. https://doi.org/10.3390/min12101206
Lin et al Response characteristics of coal subjected to coupling static and waterjet impact loads, International Journal of Rock Mechanics and Mining Sciences, Volume 103, 2018, Pages 155-167, ISSN 1365-1609,
https://doi.org/10.1016/j.ijrmms.2018.01.032.
-Wang et al Dynamic Mechanical Properties of Coals Subject to the Low Temperature-Impact Load Coupling Effect. Sci Rep 9, 20218 (2019). https://doi.org/10.1038/s41598-019-56755-7
-Zhong et al . Mechanical Properties of Roof Rocks under Superimposed Static and Dynamic Loads with Medium Strain Rates in Coal Mines. Appl. Sci. 2021, 11, 8973. https://doi.org/10.3390/app111989
- Tao et al Dynamic failure behavior and damage evolution process of holed sandstone under impact loads. International Journal of Damage Mechanics. 2023;32(1):28-49. doi:10.1177/10567895221123092.
- Zhao et al . Experimental investigation on dynamic mechanical properties and fracture evolution behavior of the underground openings with excavation damaged zones. International Journal of Damage Mechanics. 2022;31(10):1533-1561. doi:10.1177/10567895221107709
- Conclusion section seems a second abstract. Abbreviations must defined first time are used in the text.
Comments for author File: 
Comments.pdf
Author Response
The valuable comments and suggestions from editors and reviewers are highly appreciated by the authors. In the following parts, responses and details of the revisions are given according to each comment. The revisions in the revised manuscript are marked in red.
The presented work presents a number of novel insights and solid scientific findings that can be viewed as a start point for upcoming, more in-depth studies.
- All Minor revision are reported in the attached marked pdf file.
Reply: Thanks very much for the careful review. All the problems marked in the pdf file have been revised. Some explanations for them are listed as follows:
(1) The title has been changed to “Numerical Investigation on the Mechanical Behaviours and Energy Characteristics of Hard Coal Subjected to Coupled Static-dynamic Loads”.
(2) Line 97: “In addition, a pre-loading unit is mounted to apply static pre-stress before the impact test.” The pre-loading unit is used to apply pre-stress on the specimen for the static-dynamic coupled test. The numerical modelling replicated the experimental static-dynamic coupled SHPB system proposed by Li et al., as introduced in detail in the manuscript.
(3) The introduction about PFC has been revised as suggested. Thanks very much for the reviewer’s suggestion.
(4) The figure numbers are correct in Word file but they turned to be “Error! Reference source not found” in the pdf file somehow. In the revised version, we have double-checked it to make sure all figure numbers are correct.
Some small changes must be made to the submitted paper in order to improve it:
- The research novelty in the introduction section has to be clarified, the references section needs to be updated.
Reply: Thanks very much for this valuable comment. The Introduction section has been improved and more references have been cited.
- A separated discussion section can be added in order to compare obtained results with those from earlier literature studies.
Reply: Thanks very much for the reviewer’s valuable suggestion. A discussion section has been added to the revised manuscript. All the references mentioned by the reviewer have been properly cited in the Introduction section or Discussion section.
- Conclusion section seems a second abstract. Abbreviations must be defined first time are used in the text.
Reply: Thanks for the valuable suggestion. We have revised the Conclusion section. Some contents have been removed from the Abstract and Conclusion to avoid repetition. The manuscript has been carefully checked and all abbreviations have been defined.
Reviewer 2 Report
In this manuscript, based on DEM numerical method, impact tests for coal specimens at different impact speeds and static pre-stress levels were conducted to study the mechanical properties, energy characteristics and failure patterns of coal specimens under coupled static and dynamic loads. Overall, the manuscript structure is clear, and some interesting and valuable conclusions have been obtained to fill the research gap in terms of the coupled static and dynamic mechanical behaviours of coal. I would suggest its publication if the following problems can be addressed:
1. Line 176 to 183: Some numbers are missing.
2. More references related to the study are expected in Introduction.
3. Which contact model was selected in the simulation?
4. Line 171. I suppose it should be 9 times rather than 10 times.
5. In Table 1, the unit of the density should be g/cm3, not g/m3.
6. There are kinds of symbols for the pre-stress coefficient, which are “Ks”, “ks” and “ks”, respectively. They should be uniformed to avoid confusion.
7. How can you make sure the one-dimension dynamic stress theory is effective for the SHPB system when there exists pre-stress?
8. This manuscript shows that the influence of pre-stress is significant only the dynamic loading is weak. This phenomenon is interesting. Can you find some references to validate your numerical results?
Author Response
- Line 176 to 183: Some numbers are missing.
Reply: Thanks very much for the careful review. We are sorry for our carelessness. It has been corrected in the revised manuscript.
- More references related to the study are expected in Introduction.
Reply: Thanks very much for the reviewer’s valuable suggestion. More related references have been added in the Introduction section.
- Which contact model was selected in the simulation?
Reply: In the numerical modeling, the linear parallel bond model and the linear contact bond model were used for coal specimens and SHPB bars, respectively.
- Line 171. I suppose it should be 9 times rather than 10 times.
Reply: Thanks very much for the careful review. It has been corrected in the revised manuscript.
- In Table 1, the unit of the density should be g/cm3, not g/m3.
Reply: We are sorry for our carelessness. It has been corrected in the revised manuscript.
- There are kinds of symbols for the pre-stress coefficient, which are “Ks”, “ks” and “ks”, respectively. They should be uniformed to avoid confusion.
Reply: In the revised manuscript, the symbol of “ks” was used for the pre-stress coefficient.
- How can you make sure the one-dimension dynamic stress theory is effective for the SHPB system when there exists pre-stress?
Reply: The availability of SHPB system with pre-stress has been validated by many literature studies, which has been introduced in the Introduction in the revised manuscript.
- This manuscript shows that the influence of pre-stress is significant only the dynamic loading is weak. This phenomenon is interesting. Can you find some references to validate your numerical results?
Reply: Thanks for the valuable suggestion. In the revised manuscript, a discussion section has been added, where some references were cited for comparison and validation.
Round 2
Reviewer 1 Report
The authors have revised their manuscript and responded to all the points that I had raised in the previous version of the manuscript. Therefore, the manuscript can be accepted for publication
