Analysis of Secondary Fracture Law of Roof Strata and Water Inrush Potential in Close-Distance Coal Seam Mining

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript entitled “Analysis of Secondary Fracture Law of Roof Strata and Water Inrush Potential in Close-Distance Coal Seam Mining” investigates the mechanisms of secondary reactivation of the rock mass and the associated water inrush potential in close-distance coal seam mining, combining theoretical analysis, numerical simulation (3DEC), and microseismic monitoring through a case study conducted in China.

The topic is relevant, timely, and well aligned with the scope of the journal Mining, particularly with respect to operational safety, rock mechanics, rock mass stability, and hydrogeological risks associated with underground mining. The integrated approach (theoretical framework, numerical modeling, and field data) is appropriate and has the potential to contribute to the advancement of knowledge in this field.

However, despite the scientific potential of the work, the following doubts, comments, and suggestions should be addressed:

1. The manuscript frequently mixes results, interpretations, and conclusions within the same sections, which hampers critical reading. A clearer and more coherent restructuring of the paper is required.
2. The calibration of the 3DEC model using real field data (subsidence measurements, microseismic monitoring, and fracture observations) is mentioned qualitatively; however, it is not quantitatively demonstrated. A more rigorous and explicit calibration procedure should be presented.
3. Several equations are introduced without proper derivation, adequate referencing, or consistent notation. There are mathematical formatting issues and poorly defined symbols (e.g., inconsistent use of subscripts, Greek letters, and repeated variables with different meanings). For example, Eq. 13 uses the parameter Q_A, which is also mentioned as QA in line 200. A thorough revision of all equations and explicit citation of data sources in the text is strongly recommended.
4. Some figures contain excessive visual information, resulting in low readability in certain contour maps. Scales, units, and legends are not always clear or standardized and should be carefully revised.
5. The correlation between microseismic events and the evolution of hydraulic fracturing is suggested but not supported by statistical analysis. In addition, the discussion of the results lacks direct comparison with previous studies, particularly international literature, which limits the generalization of the findings.
6. A professional English language revision of the manuscript is strongly recommended.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The authors studied strata reactivation and fracturing in an overlying goaf during lower coal seam mining in a close-distance multi-seam mine, using theoretical analysis, numerical simulations, and microseismic monitoring to assess stress evolution, roof behavior, and water-inrush risk.

The manuscript is organized and relevant to the journal’s scope. The work shows merit; however, the following points should be addressed before it can be considered for publication:

• A flowchart summarizing the research methodology should be provided to improve readability.
• The limitations and possible shortcomings of the study should be clearly stated and discussed.
• A map indicating the geographical location of the studied mine should be included.
• The boundary conditions of the numerical model should be added and clearly illustrated in Figure 5.
• Further explanation is required regarding the determination of normal and shear joint stiffness values used in the 3DEC model.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Analysis of Secondary Fracture Law of Roof Strata and Water 2 Inrush Potential in Close-Distance Coal Seam Mining

 

This study investigates the mechanisms of strata reactivation and fracturing within an overlying goaf during lower seam extraction at a mine in Northwest China. Using theoretical analysis, numerical simulation, and microseismic monitoring, the research examines the secondary fracture 15 mechanisms of the goaf roof and the resulting water-inrush potential.

The work appears closer to a descriptive or exploratory study than a fully developed research article. Significant revision is required before the manuscript could be considered for publication.

-In the abstract, this sentence is not clear “This structural stiffness suppresses the expansion of both the caving 25 zone and roof subsidence 30m above the 221 coal seam increased significantly from 1.89m 26 to 5.475m.”

-At the end of the Introduction, explicitly state a research question or specific objectives

-How were the site and data selected (field measurements, reports, satellite data, etc.)

-Please add a clear description of data collection procedures, sampling strategy, analytical tools or models as well as limitations and assumptions. Without this information, the study cannot be replicated, which is a fundamental scientific requirement.

-It is not clear where the section of results begins

-How do the findings compare with previous studies. There is limited discussion of how this study confirms, contradicts, or extends existing knowledge.

-More recent references should be added

-Please describe the nomenclature for equations 1 and 2.

-In figure 7, what are the units

-Figure 12, add a color bar to show the magnitude of the vertical displacement

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

After the revisions, the manuscript has shown a substantial improvement, and all previously raised concerns have been adequately addressed. Therefore, my recommendation is that the paper be accepted in its present form.

Author Response

We sincerely appreciate the valuable feedback previously provided by the reviewer, which has substantially contributed to the enhancement of this manuscript. Once again, we extend our profound gratitude for your insightful suggestions.

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have addressed my previous comments. Before acceptance, it is recommended that they provide and cite references for Equations (26), (27) and (28).

Author Response

Comments 1: it is recommended that they provide and cite references for Equations (26), (27) and (28).

Response 1: Thank you for pointing this out. We apologize for the omission of citations for Equations (26), (27), and (28) in the original manuscript. The corresponding references have now been incorporated into the text. Equations (26), (27):Tien, Y. M., Kuo, M. C. A failure criterion for transversely isotropic rocks.International Journal of Rock Mechanics and Mining Sciences, 2001. 38(3), 399-412. Equations (28):Itasca Consulting Group. 3DEC—3-Dimensional Distinct Element Code, User’s Guide (Version 7.0). 2019.

Reviewer 3 Report

Comments and Suggestions for Authors

The comments have been addressed satisfactorily and the manuscript improved.

Author Response

We sincerely appreciate the valuable feedback previously provided by the reviewer, which has substantially contributed to the enhancement of this manuscript. Once again, we extend our profound gratitude for your insightful suggestions.