Prediction of Water Inrush Hazard in Fully Mechanized Coal Seams’ Mining Under Aquifers by Numerical Simulation in ANSYS Software

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

applsci-3563887-review

Prediction of water inrush hazard in fully mechanized coal seams’ mining under aquifers by numerical simulation in ANSYS software

This study proposes algorithm for assessment of the risk of water inrush from aquifer based on an ANSYS simulation in complex anticline coal seam bedding. The specific opinions and suggestions are as follows:

1.The abstract of the paper needs to be rewritten to highlight the innovation of the research methods and results.

2.Most of the illustrations are not standardized enough, lacking important information such as legends, color codes, and scales, resulting in poor readability. It is necessary to further modify all the images in the paper according to the requirements of the journal.

3.The writing of the conclusion is not rigorous enough and does not fully summarize the innovative results of the paper. Just a brief listing of the aforementioned content.

4.There seems to have been serious water inrush accidents in the research area, but the evaluation results show that the risk is very low. How to verify the accuracy of evaluation results.

5.The author mentioned how the risk of water inrush evolved when directional drilling and grouting were used to transform the coal seam roof in the research area, and further discussion should be conducted.

6.There are many non-standard and imprecise expressions in the English of the paper, and it is recommended to further polish it.

 

 

 

Author Response

Thank you very much for taking the time to review this manuscript. We appreciate the constructive suggestions, which have been valuable and helpful for revising and improving our paper. We have seriously considered all the questions/comments from Reviewers #1, and revised the manuscript as possible as we can, in which the new analysis is highlighted in the text. The part modified according to the reviewer 's Comments is highlighted in red.

Comments1.

1.The abstract of the paper needs to be rewritten to highlight the innovation of the research methods and results.

Response 1. Thank you for pointing this out. The abstract of the paper was rewritten. Сorrected text was highlighted in red.

In addition, the introduction section has been revised to emphasize the novelty of this paper.

Comments 2. Most of the illustrations are not standardized enough, lacking important information such as legends, color codes, and scales, resulting in poor readability. It is necessary to further modify all the images in the paper according to the requirements of the journal.

Response 2. Thank you for pointing this out. The authors carefully reviewed all figures. Figures 8, 12-14, 15 were corrected. If the reviewer has specific comments on the figures, please indicate them more specifically.

Comments 3.The writing of the conclusion is not rigorous enough and does not fully summarize the innovative results of the paper. Just a brief listing of the aforementioned content.

Response 3. Thank you for your suggestion. The authors have made changes to the conclusion section. The third paragraph has been shortened to reduce repetition.

Comments 4.There seems to have been serious water inrush accidents in the research area, but the evaluation results show that the risk is very low. How to verify the accuracy of evaluation results.

Response 4. Thank you for your suggestion. This study examines a 817 longwall located near the 815 accident longwall. During the excavation of the 815 longwall panel the distance to the aquifer is the shortest. Consequently, the risk of establishing a hydraulic connection with the aquifer is maximal. The location of stop mining line of 815 longwall allows to make an assessment of the spatial relationship between the working face, fault and aquafier at the moment of water inrush and to identify its primary causes. One of the causes is the influence of 815F16 fault (the predicted position of this fault is marked in red dashed line in Fig. 5). The steep inclination of the fault at 78 degrees and its large displacement (7.5 meters) leads to the formation of a downward water migration path, even in the absence of hydraulic pressure. The analysis of fault parameters near 817 longwall suggests that the water inflow through faults is unlikely, since faults with steep inclination and large displacement (like 815F16 fault) are not detected by the geological forecast.

Thus, during the extraction of future longwall panels, the highest risks of water inrush are associated with extraction of 817 longwall. At the same time the most hazardous thing is inflow through the water-conducting fracture zone. This conclusion is based on the geological assessment and the adoption of the mechanistic concept of hazardous sections as a risk criterion.

“Fulfilment of 1-7 points of the proposed algorithm does not show the risk of water breakthrough over the 815 longwall panel. However, such a risk can be predicted based on point 8. The lack of a reliable forecast of the spatial orientation of the fault does not allow to enter it into the model for a more accurate analysis. The geometry of the model can be adjusted when spatial orientation of the fault is known”.

The above text has been added to the discussion section and highlighted in red.

 

Comments 5.The author mentioned how the risk of water inrush evolved when directional drilling and grouting were used to transform the coal seam roof in the research area, and further discussion should be conducted.

Response 5. Thank you for your suggestion. The experience of successful implementation of the water inrush control method by horizontal regional grouting through multiple directional wells is described in the paper. It is not clear from the reviewer's comment what specific discussions should be added.

Comments 6.There are many non-standard and imprecise expressions in the English of the paper, and it is recommended to further polish it.

Response 6. Thank you very much for this important suggestion. Agree. Revised.

The English language has been carefully corrected. Changes of the text are highlighted in red.

Reviewer 2 Report

Comments and Suggestions for Authors

This study presents a method for predicting and controlling the risk of water inrush during coal mining beneath aquifers. The research applies grouting through multiple directional wells and numerical simulation using ANSYS software to analyze the stress-strain state of the surrounding rock in the Xinhu Coal Mine. As a result, the goaf area and the longwall panel boundary were identified as potentially hazardous zones for rock failure. Based on the calculated stress and strain safety factors, the rock mass near the aquifer was found to be generally stable, with a low probability of failure. Furthermore, an 8-step algorithm for evaluating water inrush risk was proposed and tested. This algorithm can serve as a predictive and preventive tool for similar geological conditions in other mining sites. To meet the requirements for publication, the following revisions are recommended

 

1) Several sentences in the Abstract lack clear subjects and objects. While simplification is acceptable in an abstract, the absence of grammatical components hinders clarity. Please revise the sentence structures to ensure that the key points of the research are clearly conveyed.

2) This study conducts a numerical simulation for the unmined 817 longwall panel. However, it is unclear whether a similar simulation was performed for the 815 panel where an actual water inrush incident occurred. If the proposed algorithm failed to predict water inrush in the 815 panel, then the reliability of the 817 analysis could be questioned. Please provide a detailed explanation to reinforce the credibility of the 817 analysis.

3) The Introduction lacks a comprehensive literature review on water infiltration. Please elaborate on previous cases of water-related incidents, existing mitigation techniques, and their limitations to justify the significance of this study.

4) Furthermore, the Introduction should include a more thorough discussion of countermeasures against water infiltration, including the application and economic feasibility of grouting techniques. A comparison between existing grouting methods and the proposed approach would help clarify its practical advantages.

5) Section 3.3 presents results based solely on the conditions of the 817 panel. The lack of sensitivity analysis for material properties, caved and fractured zone heights, limits the reliability of the interpretation. Additional simulations under varied conditions or for other panels are needed to validate the robustness of the results.

6) In the Discussion, Figure 15 is used to illustrate the relationship between safety factors and rock failure probability. However, the theoretical basis, application scope, and validation of this chart are not sufficiently explained. Please clarify the model's assumptions, applicability, and previous verification studies.

7) While the proposed algorithm is systematic, its novelty and advantages over existing methods are not clearly discussed. A comparative analysis with prior studies would help emphasize the algorithm's originality and improvements.

8) The displacement and strain graphs in the manuscript lack consistent formatting, making it difficult to compare values. In some figures, axis labels overlap with plots, reducing legibility. Please standardize the formatting of all graphs to improve readability and visual consistency.

Author Response

Thank you very much for taking the time to review this manuscript. We appreciate the constructive suggestions, which have been valuable and helpful for revising and improving our paper. We have seriously considered all the questions/comments from Reviewers #2, and revised the manuscript as possible as we can, in which the new analysis is highlighted in the text. The part modified according to the reviewer 's Comments is highlighted in red.

Comments1.

1) Several sentences in the Abstract lack clear subjects and objects. While simplification is acceptable in an abstract, the absence of grammatical components hinders clarity. Please revise the sentence structures to ensure that the key points of the research are clearly conveyed.

Response 1. Thank you for pointing this out. The abstract of the paper was rewritten. Сorrected text was highlighted in red.

Comments 2) This study conducts a numerical simulation for the unmined 817 longwall panel. However, it is unclear whether a similar simulation was performed for the 815 panel where an actual water inrush incident occurred. If the proposed algorithm failed to predict water inrush in the 815 panel, then the reliability of the 817 analysis could be questioned. Please provide a detailed explanation to reinforce the credibility of the 817 analysis.

Response 2. Thank you for pointing this out. This study examines a 817 longwall located near the 815 accident longwall. During the excavation of the 815 longwall panel the distance to the aquifer is the shortest. Consequently, the risk of establishing a hydraulic connection with the aquifer is maximal. The location of stop mining line of 815 longwall allows to make an assessment of the spatial relationship between the working face, fault and aquifer at the moment of water inrush and to identify its primary causes. One of the causes is the influence of 815F16 fault (the predicted position of this fault is marked in red dashed line in Fig. 5). The steep inclination of the fault at 78 degrees and its large displacement (7.5 meters) leads to the formation of a downward water migration path, even in the absence of hydraulic pressure.

“Fulfilment of 1-7 points of the proposed algorithm does not show the risk of water breakthrough over the 815 longwall panel. However, such a risk can be predicted based on point 8: "Additional assessment of the influence of faults with steep dip angles and large displacement". The lack of a reliable forecast of the spatial orientation of the fault does not allow to enter it into the model for a more accurate analysis. The geometry of the model can be adjusted when spatial orientation of the fault is known.”

The text above has been added to the discussion section and highlighted in red.

Comments3) The Introduction lacks a comprehensive literature review on water infiltration. Please elaborate on previous cases of water-related incidents, existing mitigation techniques, and their limitations to justify the significance of this study.

Response 3. Thank you for this important suggestion. Revised. The next text and table were added in introduction section, and highlighted in red.

Liang et al. [2], based on the analyse of statistics, summarized that a total of 1,196 major water inrush accidents occurred in China in the past 20 years (Table 1), resulting in 4,775 deaths and disappearances, and direct economic losses of more than tens of billions of yuan.

Table 1. Summary of major water inrush incidents [2].

Coal Mines Name	Sudden water          time	Maximum surge capacity（m3/h）	Hydrogeological features	Impact
Cuimu Mine	2013	1300	Water in the Yijun For- mation sandstone and Luohe Formation sandstone aquifers	Discontinued
Guojiahe Coal Mine	2016	2300	Water in the Yijun For- mation sandstone and Luohe Formation sandstone aquifers	Discontinued
Yuanzigou Coal Mine	2019	570	Water in the Yijun For- mation sandstone and Luohe Formation sandstone aquifers	Discontinued
Gaojiabao Coal Mine	2015	3000	Low River Formation Sand- stone Aquifer	Discontinued
Zhaojin Coal Mine	2013 2016	-	Rock River Formation Sandstone Fissure Aquifer	11 deaths
Yangliu Coal Mine	2017	-	Water in the Sandstone Aq- uifer of the Stone Box For- mation	Potential threats
Fangezhuang Coal Mine	2016	60	Hydraulic fracture zones, sandstone fracture bearing aquifers	No impact
Daliu Coal Mine	2013	430	Water-conducting fracture zones, geological for- mations	Discontinued
Wanglou Coal Mine	2013	1345.7	Jurassic sand and conglom- erate fissure aquifer	Discontinued
Lijialou Coal Mine	2016	3158	Water conductive rift zone	Discontinued
Shajihai Coal Mine	2016	-	Water from the Headunhe Formation aquifer, water from the Xishangyao For- mation medium-coarse sandstone aquifer	Discontinued
Shilawusu Coal Mine	2018	921.4	Cretaceous Luohe For- mation sandstone aquifer	Discontinued

 

Comments 4) Furthermore, the Introduction should include a more thorough discussion of countermeasures against water infiltration, including the application and economic feasibility of grouting techniques. A comparison between existing grouting methods and the proposed approach would help clarify its practical advantages.

Response 4. Thank you for pointing this out. In this study, the authors considered cases of water breakthrough from aquifer, focusing on the cases of powerful aquifers. In such conditions, drainage systems cannot cope with the volumes of water and mud, as shown in the example of Xinhu Coal Mine. The Introduction focuses on modern concepts and methods for forecasting water inflows, since this is the main topic of the study presented in the article.

Comments 5) Section 3.3 presents results based solely on the conditions of the 817 panel. The lack of sensitivity analysis for material properties, caved and fractured zone heights, limits the reliability of the interpretation. Additional simulations under varied conditions or for other panels are needed to validate the robustness of the results.

Response 5. Thank you for this important suggestion. The authors agree that validation of the modeling results would improve its accuracy. Unfortunately, in this study it was not possible to measure the height of the fractured zones above the goaf, so the authors used theoretical results and the results of their previous studies.

Revised. The next sentences were added in paper (section 3.2), and highlighted in red.

The model width was pre-optimized by testing the sensitivity of the model by the stress factor.

The basis for such an assumption was the research of Borisov S.S., Kuznetsov G. N., Ogloblin D. M. In addition, such a model was validated with the results of field measurements, which was shown in previous studies [12, 30].

Comments 6) In the Discussion, Figure 15 is used to illustrate the relationship between safety factors and rock failure probability. However, the theoretical basis, application scope, and validation of this chart are not sufficiently explained. Please clarify the model's assumptions, applicability, and previous verification studies.

Response 6. Thank you for this important suggestion.

Unfortunately, at this present moment in time there are no generally accepted laws linking safety factors and probabilities of rock mass failure. Therefore, in this paper, the relationships between safety factors and probabilities of rock mass failure obtained in the researches of slope stability by the following authors were used:

MacRobert, C. J. Factors of safety and probabilities of failure in geotechnical engineering: What do we mean? Civil Engineering 2018, 26(3), 45-50.

Gover, S M 2017. Linking safety factor to probability of failure. Proceedings, 9th South African Young Geotechnical Engineers Conference, SAICE, 93–102.

Hubble, T C T 2010. Improving the stream of consciousness: A nomenclature for describing the factor of safety in river bank stability analysis. Ecological Engineering, 36: 1765–1768. doi: 10.1016/j.ecoleng.2010.07.001.

Lambe, T W, Silva, F & Lambe, P C 1988. Expressing the level of stability of a slope. The Art and science of geotechnical engineering: at the dawn of the twenty-first century: a volume honoring Ralph B. Peck, R B Peck & E J Cording, eds. Prentice Hall, 558–588.

Comments 7) While the proposed algorithm is systematic, its novelty and advantages over existing methods are not clearly discussed. A comparative analysis with prior studies would help emphasize the algorithm's originality and improvements.

Response 7. Thank you for pointing this out. Analysis of previous studies did not allow the authors to find similar algorithms for comparison. Therefore, the authors believe that:

The main novelty of this paper is the development of the algorithm for the assessing the risk of water inrush from aquifer based on an ANSYS simulation in complex anticline coal seam bedding.

The text above has been added to the introduction section.

Comments 8) The displacement and strain graphs in the manuscript lack consistent formatting, making it difficult to compare values. In some figures, axis labels overlap with plots, reducing legibility. Please standardize the formatting of all graphs to improve readability and visual consistency.

Response 8. Thank you for pointing this out. Figures 12, 14 have been revised.

 

Reviewer 3 Report

Comments and Suggestions for Authors

After reviewing the manuscript, I have the following questions, comments, and suggestions:
1.    In the literature review, it is worth mentioning the theory by W. Budryk and S. Knothe.
2.    2.    Why does the numerical model have a length of 200 m? The same problem could be solved with a planar model, or spatial, for example 1 meter long.
3.    Lines 313–314: On what basis was it assumed that "The height of the caved zone was equivalent to eight times the thickness of the coal seam, and the height of the fractured zone – to twenty times the seam thickness"?
4.    It should be stated that the calculations were performed using an elastic model, which is a significant simplification compared to the actual behavior of the rock mass.
5.    Line 316: What does "pseudo-elastic" mean?
6.    Table 1: In what directions were the individual parameters (E₁, E₂, E₃) of the anisotropic model set?
7.    Fig. 7: There are no marks a, b, c.
8.    Fig. 7c: In my opinion, there should be a small upward displacement on the floor of the mined coal seam. I do not see such displacement in Figure 7c.
9.    Fig. 8: There are only two drawings, a and b, while the caption mentions three: a, b, and c.
10.    Fig. 8a: Why does dark blue cover such a large part of the model? I believe the increase in vertical stress should be similar throughout the entire model.
11.    Fig. 8a: Vertical stress can be calculated by multiplying the rock mass density by depth. According to this calculation, the maximum vertical stress in the model should be 814 meters multiplied by 24 kN/m³ (approximately), resulting in 19.54 MPa. Why does Figure 8a show a maximum stress of 13.7 MPa?
12.    Fig. 8b: The color scale should be adjusted to clearly show the location of the highest stresses, which reach 63.7 MPa.
13.    Line 396: Why do you consider the cumulative error value of 5.79% to be sufficient, and not more or less?
14.    Lines 532–543 and 586–596: These sections are identical; you only need to include them once.

Author Response

Thank you very much for taking the time to review this manuscript. We appreciate the constructive suggestions, which have been valuable and helpful for revising and improving our paper. We have seriously considered all the questions/comments from Reviewers #3, and revised the manuscript as possible as we can, in which the new analysis is highlighted in the text. The part modified according to the reviewer 's Comments is highlighted in red.

Comments1.

1. In the literature review, it is worth mentioning the theory by W. Budryk and S. Knothe.

Response 1. Thank you for this important suggestion. The theory by W. Budryk and S. Knothe was added in paper, and highlighted in red.

Budryk and Knothe [13] proposed the subsidence theory for the Upper Silesia region conditions. According to Budryk and Knothe [13] the maximum predicted subsidence is equal to thickness of excavating seam multiplied by exploitation parameter a (values between 0 and 1). The maximum area of exploitation influences contains mining area and area in the influence range of exploitation. The depth of seam and the rock mass parameter tan(β) (where β is the angle of main influences) should be known to compute the range of exploitation. With known values of maximal subsidence and range of exploitation, one can compute the inclination in the distance from the edge of exploited seam. For standard geological conditions of Upper Silesia Coal Basin, the assumption of tan(β) = 2 is usually made [14]. The Budryk and Knothe [13] subsidence scheme is a classical one. Similar subsidence schemes are used in different coal regions of the world. In particular, they form the basis of current regulatory documents of Ukraine [15].

Comments 2.  Why does the numerical model have a length of 200 m? The same problem could be solved with a planar model, or spatial, for example 1 meter long.

Response 2. Thank you for your professional opinion. The authors fully agree with this point of view. Moreover, in previous studies we used a model thickness of 1.0 m. However, reviewers too often return papers with thin models, so to be on the safe side we started to use volumetric models. Although we understand that the result will not change from this, and the calculation time will increase significantly.

Comments 3.    Lines 313–314: On what basis was it assumed that "The height of the caved zone was equivalent to eight times the thickness of the coal seam, and the height of the fractured zone – to twenty times the seam thickness"?

Response 3. Thank you for this important suggestion. Revised. The text was added in paper, and highlighted in red.

The basis for such an assumption was the research of Borisov S.S., Kuznetsov G. N., Ogloblin D. M. In addition, such a model was validated with the results of field measurements, which was shown in previous studies [12, 30].

Comments 4.    It should be stated that the calculations were performed using an elastic model, which is a significant simplification compared to the actual behavior of the rock mass.

Response 4. Thank you for this important suggestion. The authors agree that the elastic model does not reflect the actual behavior of the rock mass. However, long-term numerical modeling of the subsidence processes in Ansys software, conducted by the authors, shows that the orthotropic model is the most accurate for subsidence studies from the available models. Similar conclusions have been obtained by other researchers, for example:

1. Khanlari, G.; Rafiei, B.; Abdilor, Y. Evaluation of strength anisotropy and failure modes of laminated sandstones. Arab. J. Geosci.2015, 8, 3089–3102.
2. Dudek, M.; Mrocheń, D.; Sroka, A.; Tajduś, K. Integrating the Finite Element Method with Python Scripting to Assess Mining Impacts on Surface Deformations. Appl. Sci.2024, 14, 7797. https://doi.org/10.3390/app14177797

This is precisely why this model was used in the study.

Comments 5.    Line 316: What does "pseudo-elastic" mean?

Response 5. Thank you for pointing this out. The term "pseudo-elastic" is used to emphasize that in reality the behavior of rock masses is not elastic. This is a kind of assumption.

Comments 6.    Table 1: In what directions were the individual parameters (E1, E2, E3) of the anisotropic model set?

Response 6. Thank you for this important suggestion. Revised. The text was added in paper, and highlighted in red.

The directions of E1, E2, E3 in the anisotropic model corresponded to the direction of the axes OX (horizontal), OY (vertical), OZ (horizontal).

Comments 7.    Fig. 7: There are no marks a, b, c.

Response 7. Thank you for your suggestion. Agree. Revised.

 

Comments 8.    Fig. 7c: In my opinion, there should be a small upward displacement on the floor of the mined coal seam. I do not see such displacement in Figure 7c.

Response 8. Thank you for pointing this out. You are right. However, the displacement step (can be seen at the legend) does not allow to see this uplift.

Comments 9.    Fig. 8: There are only two drawings, a and b, while the caption mentions three: a, b, and c.

Response 9. Thank you for your suggestion. Agree. Revised.

Comments 10.    Fig. 8a: Why does dark blue cover such a large part of the model? I believe the increase in vertical stress should be similar throughout the entire model.

Response 10. Thank you for pointing this out. Agree. Revised.

You are right. The stresses in the rock masses, caused by gravity, increase uniformly. The step of the stress scale was set manually, so as to show the pattern in the roof in more detail. Therefore, in Fig. 8a there is disproportionately more dark blue (the step of the color scale is indicated in the legend).

In the process of preparing the figure for the paper, the scale signatures were adjusted manually. The authors made an inaccuracy: the lower limit of the range is not 13.7 MPa but 19.7 MPa.

Comments 11.    Fig. 8a: Vertical stress can be calculated by multiplying the rock mass density by depth. According to this calculation, the maximum vertical stress in the model should be 814 meters multiplied by 24 kN/m³ (approximately), resulting in 19.54 MPa. Why does Figure 8a show a maximum stress of 13.7 MPa?

Response 11. Thank you for pointing this out. Agree. Revised.

In the process of preparing the figure for the paper, the scale signatures were adjusted manually. The authors made an inaccuracy: the lower limit of the range is not 13.7 MPa but 19.7 MPa.

Comments 12.    Fig. 8b: The color scale should be adjusted to clearly show the location of the highest stresses, which reach 63.7 MPa.

Response 12. Thank you for pointing this out. The maximum of vertical stresses is located above the edge of the longwall (abutment pressure). This study does not contradict the traditional idea of the stress distribution around the longwall. The stress scale is adjusted to show the change in the stress diagram after the coal seam in longwall is extracted. The stress distribution along the monitoring lines (Fig. 13a) shows the axis of maximum stresses. Your opinion is very valuable to us, however, according to the authors, reconfiguration of the scale is not required.

Comments 13.    Line 396: Why do you consider the cumulative error value of 5.79% to be sufficient, and not more or less?

Response 13. Thank you for your suggestion. Agree. Unfortunately, the authors do not know of a single criterion for accuracy. Analysis of studies of numerical simulation of geomechanical processes published in high-impact journals shows that with an accuracy of models up to 10%, a conclusion is usually made about the sufficient adequacy of the models. The authors will be grateful to the reviewer for a hint regarding the permissible accuracy of numerical models in mining.

Comments 14.    Lines 532–543 and 586–596: These sections are identical; you only need to include them once.

Response 14. Thank you for pointing this out. Agree. Revised.

Reviewer 4 Report

Comments and Suggestions for Authors

The study submitted for review is devoted to the problem of mine safety - water inrush in fully mechanized coal seams under aquifers. The study focuses on the risks of water-conducting zone cracks and their impact on the safety of mine operations. Given the frequency of accidents in coal mines, the topic of the study is relevant.

In the first section of the manuscript, the literature review is presented comprehensively. The authors cover classical approaches to analyzing roof collapse in coal seams, including the "vertical line theory", the "arch theory", the "zonal theory", the "premature failure hypothesis", and the "layered beam model". Along with modern approaches, such as the "key strata theory", this provides a solid scientific foundation for the study. The research objective is clearly formulated: assessing the risk of water inrush through numerical modeling in ANSYS.

The research methodology is based on numerical modeling. The competent use of the ANSYS software package allows for a detailed analysis of the stress-strain state of the rock massif and an assessment of the probability of water breakthrough. The originality and novelty of the research is manifested in the combination of numerical modeling and real geological conditions of the Xinhu mine, as well as in the application of a safety criterion based on stress and strain parameters.

The modeling results indicate a low risk of the formation of a water-conducting zone of cracks in the considered mine. Figures 12, 13 and 14 demonstrate the distribution of stresses and strains in the rock massif. They well illustrate the conclusions of the study. This is an important conclusion for further mining planning and the implementation of safety measures.

It should be noted that scientists from European universities are involved in solving problems that are of critical importance for the mining industry of East Asia. Such international cooperation deserves high praise, as it contributes to the exchange of advanced technologies and experience.

In general, the presented manuscript is an original scientific study, and the obtained results have practical significance for ensuring the safety of coal mines. I recommend accepting the article for publication after minor revisions. Comments and recommendations are given below.

There are several comments and recommendations to the text of the manuscript.

1.What is the impact of the choice of boundary conditions in the model on the results of water permeability forecasting? Did the authors test the sensitivity of the model to changes in these parameters? The presence or absence of such results should be reported to the potential reader. Also, the text should more clearly emphasize the criteria used to conclude on the risk of water breakthrough.

2.The method proposed by the authors involves affecting the geomechanical state of the massif. Injecting materials into cracks can change their configuration, which in turn can likely affect the spread of water. It is important to evaluate whether the study takes into account the possible side effects of this approach. This leads to the following question. Could the method of horizontal tamping through multi-directional wells itself cause additional cracks and changes in the permeability of the massif? If such a possibility exists, it should be mentioned in the text.

3.The manuscript presents an approach to minimizing the risk of water breakthrough, but its effectiveness may significantly depend on the economic feasibility of implementing the proposed measures. Has a comparative analysis of the costs of implementing this method been carried out in comparison with alternative strategies, in particular, pre-mining dewatering (e.g., drainage systems)? It would be useful to include in the study a recommendation on the choice of this method, taking into account hydrogeological conditions, scale of development and economic feasibility.

Comments for author File: Comments.pdf

Author Response

Thank you very much for taking the time to review this manuscript. We appreciate the constructive suggestions, which have been valuable and helpful for revising and improving our paper. We have seriously considered all the questions/comments from Reviewers #4, and revised the manuscript as possible as we can, in which the new analysis is highlighted in the text. The part modified according to the reviewer 's Comments is highlighted in red.

Comments1.

1. What is the impact of the choice of boundary conditions in the model on the results of water permeability forecasting? Did the authors test the sensitivity of the model to changes in these parameters? The presence or absence of such results should be reported to the potential reader. Also, the text should more clearly emphasize the criteria used to conclude on the risk of water breakthrough.

Response 1. Thank you for your suggestion. Agree.

The numerical model has a length of 200 m. According to the authors, the same problem could be solved with a planar model, or spatial, for example 1 meter long. However, the comments of reviewers in previous publications often indicated that preference should be given to volumetric models.

The vertical size of the model is determined by geology. As for the width of the model, the model was preliminarily optimized by testing the sensitivity of the model.

Revised. The next text was added in paper, and highlighted in red:

"The model width was pre-optimized by testing the sensitivity of the model by the stress factor".

« Thus, it is proposed to use probability of rock failure based on safety factors as criteria for the risk of water inrush."

Comments 2.The method proposed by the authors involves affecting the geomechanical state of the massif. Injecting materials into cracks can change their configuration, which in turn can likely affect the spread of water. It is important to evaluate whether the study takes into account the possible side effects of this approach. This leads to the following question. Could the method of horizontal tamping through multi-directional wells itself cause additional cracks and changes in the permeability of the massif? If such a possibility exists, it should be mentioned in the text.

Response 2. Thank you for your comment. Unfortunately, the authors did not consider these issues in their study. The reviewer's advice will be taken into account in future studies.

Comments 3.The manuscript presents an approach to minimizing the risk of water breakthrough, but its effectiveness may significantly depend on the economic feasibility of implementing the proposed measures. Has a comparative analysis of the costs of implementing this method been carried out in comparison with alternative strategies, in particular, pre-mining dewatering (e.g., drainage systems)? It would be useful to include in the study a recommendation on the choice of this method, taking into account hydrogeological conditions, scale of development and economic feasibility.

Response 3. Thank you for your deep comments and suggestions for improving the article.

In this study, the authors considered cases of water breakthrough from aquifer, focusing on cases of powerful aquifers. In such conditions, drainage systems cannot cope with the volumes of water and mud, as shown in the example of Xinhu Coal Mine. An alternative to the surface-based method is grouting from underground mine roadways. In this case, the total drilling costs would be significantly lower. According to preliminary estimates, the cost of drilling work can be reduced by about 5 times. However, many technological problems arise with the delivery of cement mixture to the mine and the implementation of effective underground injection. The lack of a clear project indicating the equipment does not allow obtaining sufficiently accurate economic estimates. In addition, the authors do not have the right to disclose any commercial information related to the described project. Therefore, the article focuses on the scientific component of the project.

Reviewer 5 Report

Comments and Suggestions for Authors

Dear Authors
You have presented a very interesting work at a high technical level. Unfortunately, there are many errors in the text that need to be corrected. I kindly ask you to read the attachment, where language corrections have been made by hand.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The English style is at average level,  there are many errors. You have to correct them

Author Response

Thank you very much for taking the time to review this manuscript. We appreciate the constructive suggestions, which have been valuable and helpful for revising and improving our paper. We have seriously considered all the questions/comments from Reviewers #5, and revised the manuscript as possible as we can, in which the new analysis is highlighted in the text. The part modified according to the reviewer 's Comments is highlighted in red.

Comments1. Dear Authors
You have presented a very interesting work at a high technical level. Unfortunately, there are many errors in the text that need to be corrected. I kindly ask you to read the attachment, where language corrections have been made by hand.

Response 1. Dear Reviewer

 Thank you for your comment. You have done a great job. We have added all your corrections to the manuscript. Huge thanks for your meticulousness and your work!

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

 Accept in present form

Reviewer 3 Report

Comments and Suggestions for Authors

After corrections the manuscript is suitable for publication.