Simulation Experimental Investigations into the Mechanical Response and Failure Mechanisms of Coal–Rock Combinations

Round 1

Reviewer 1 Report

This paper investigates the mechanical behavior of coal-rock combination through the physical compression testing numerical simulation. The mechanical response and failure mechanism of coal-rock combination were comprehensively investigated. Although the topic is very interesting, but the manuscript is very poorly written and presented. Applying the following comments and suggestions will improve the current version of the manuscript.

·       Abstract is unclear. it is hard to highlight more important information. Abstracts usually have at least one sentence per each: context and background, motivation, hypothesis, methods, results, conclusions.

·       Introduction section lack critical review of the previous literature.

·       According to the available technical literature concerning this paper, article innovation is missing in comparison with other research works.

·       At the end of introduction, add a brief para describing the paper organization.

·       Related works should include more latest references about the subject investigated.

·       How does the accuracy of test results were ensured?

·       On what bases the height ratios (of the sand-stone: coal) used in the experiment were selected?

·     Line 98-99: " with AB super glue ϕ50 × 100 mm standard pieces are employed……", which standard the authors are referring?

·       It is recommended to add a brief description of the procedure of the adopted uniaxial compression test.

·       Discussion of the results presented in Figure 2 is missing.

·       What was the source of the model presented in Figures 3 and 4?

·        What is the reason behind putting a bar above each variable?

·       Results lacks the quantitative discussion.

·  Conclusions should be curtailed summarizing only key points. Further study limitations should be added.

·       The linguistic quality of the paper also warrant improvement.

Moderate editing of English language required

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

Dear author, my observations are in the following lines:

Include references between lines 58 and 60.

Put Table 1 before Figure 1 in the manuscript.

Include references about the software between lines 126 and 129.

Review the complete paper and check of all symbols are included with their respective description.

Include in the analysis of each part, the comparison with other works in the same area.

1. The main question is how much can fit the data to numerical simulation in the case of coal rock combination.

2. In my opinion, the research is interesting and could be relevant incorporating modifications.

3. The methodology is too extensive, it is quite complete, but the reading is complex, and I can detect several mistakes.

4. Are the conclusions consistent with the evidence and arguments presented and do they address the main question posed? Yes, but they are too general. I am not qualified to evaluate the language, but the paper seems too difficult to understand and a language and redaction review could be necessary.

5. The references are scarce in some paragraphs, and they need to be complemented.

6.  The position of tables and figures must be reviewed.

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

The paper deals with experimental tests and numerical simulations of coal-rock layered cylindrical specimens, with respect to various mechanical responses, toward the understanding of the respective constitutive behaviour and cracking-failure mechanisms.

The research subject is nowadays of significant interest for the engineering community, also for practical applications.

However, the present form of the article may be revised according to the following observations:

- the full-text should be accurately revised to properly explain the developed research;

- in particular, the Introduction section should properly pose the devised approach with respect to an extensive literature survey;

- the sections devoted to numerical simulations and comparisons (3, 4 and 5) should describe, in details, the adopted materials, models and computational methods;

- the Conclusion section is expected to derive effective conclusions, also highlighting the innovative contributions, possibly avoiding the numbered list format close to technical report style;

- moreover, the proposed approach seems not to consider any scale size effect (particularly significant with respect to fracture behaviour): such issue is expected to be analysed and discussed in details, particularly with reference to the numerical models and simulations, also aiming at real case applications to bigger size case study conditions;

- as for graphical quality of diagrams, an improved readability and explanation of the results may be suggested.

An accurate revision of the full text is highly suggested to improve readability (English language form) and to remove several mistakes/misprints.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The manuscript has been significantly improved. I would like to recommend the article for publication. 

Author Response

Dear Reviewer,

We would like to heartily thank you for recommend the article for publication. Your academic sense and scientific literacy definitely allowed us to improve the level of this manuscript. We highly appreciate your time and effort. Those comments are very valuable and helpful for revising and improving our paper, as well as the important guiding significance to our researches.

Reviewer 3 Report

The revised version of the manuscript appears to be improved.

However, in this reviewer's opinion, some suggestions shall be considered, also with reference to previous Reviewers' observations.
In particular:
- size effect (particularly referring to fracture behaviour) has to be considered; if not considered, such limitation should be clearly stated, since it significantly diminishes the study meaningfulness;
- most of the figures (and tables) shall be improved in graphical quality, readability of the results, explanations of legends and description in captions;
- the conclusion section is expected to be as a clear and effective text, preferably avoiding point-wise report style.

English language may be improved in clearness and effectiveness (e.g., more explanatory title, more fluent Conclusions).

Author Response

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Author Response File: Author Response.docx

Round 3

Reviewer 3 Report

The revised version appears not to effectively consider Reviewers' suggestions. Despite clear answers in the cover letter, the Authors introduced very limited modifications in the paper (as an example, while it was suggested, and agreed in the cover letter, to improve the Conclusion sections, the only changes are the removal of numbering indexes and of a sentence from the closing ones).

Please, see Comments and Suggestions for Authors.

Author Response

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Author Response File: Author Response.pdf