Study on the Partial Paste Backfill Mining Method in a Fully Mechanized Top-Coal Caving Face: Case Study from a Coal Mine, China

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear authors

Thank you very much for giving the opportunity to review this manuscript. Although it is well organized,  many points require revisions. Common and specific comments are listed above:

Common comments

1- The quality of English is not satisfactory for publication. The manuscript contains numerous unclear sentences (particularly in sections 1-3), which limits its readability. It is highly recommended to reevaluate the manuscript from the point of proofreading. 

2- Please state the main motivation for preparing the manuscript more clearly, although you have mentioned that in the literature, there is a lack of information on partial backfilling technology in top coal longwall mining. To do this, you may unveil the meaning of a new partial backfill method. It means that in the literature, there is a partial backfill method applicable to top coal longwall mining. What do you need to propose a new partial backfill method? What are the theoretical advantages of implementing the partial backfill method?

3- Almost all of the figures don't have additional explanations, scale bars and information in existing legends (e.g., Figure 14: Unit: m but what does the legend mean? Does it mean vertical displacement? Consider all the figures in the manuscript based on this comment. 

4- When tackling with top coal longwall mining, you should give a plan view and some cross-sections depicting the fundamentals of top coal longwall coal mining and the problem handled. Herein, you may consider the e-book: Proceedings of the International Conference on Innovations for Sustainable and Responsible Mining, ISRM 2020 - Volume 1

Specific comments:

1- As far as I am concerned, Figure 1 illustrates a plan view of the backfill area.  However, it is not appropriate to include such dots representing the cyclic filling steps, as you have shown. While presenting any representation of a longwall coal mine, I recommend you present a cross-section and a plan view together. Please don't forget to give the scale bar of any figures. 

2- In Figure 2, please give additional information or comment on what the expressions mean. For example, q may be the load of the immediate roof etc. 

3- Eqs 1 - 10 are not clear and easy to understand. Explanations on the issue are missing. What did the authors state in such equations? Did you implement these equations? If so, indicate them in the results and discussion section. If you did not implement these equations, you don't need to give them in the manuscript. 

4- There is a problem in Table 1. You have written in the title that "mechanical parameters of the coal-bearing strata and rock mass. However, rock mass properties such as elastic modulus (e.g. 25 GPa) can not be as you have given. It could be the elastic modulus of intact rock, not rock mass. Please try to understand the difference between the intact rock and rock mass. If you want to give some rock mass properties, you should give the failure criterion such as Mohr-Coulomb or generalized Hoek-Brown. 

5- In Figure 3, there are problems when representing the coal measure rocks. For example, the symbol of + is only valid for granitic rocks not for sandstones. It is not true from the viewpoint of geological engineering principles. 

6- In Figure 4, give additional information on the numbers stated. 

7- In Figure 5, there are some legends representing the stress levels around the longwall coal mine. However, these values in the legend seem to be unlogical. xxx 10^7 MPa means xxx10^4 GPa which seems unlogical. Please check the legends.

8- Please rewrite the conclusion section by considering the findings obtained from the present study. What was the main motivation for preparing this manuscript, and what did you find? You should also give some comments to the audience for further studies including partial backfill technology in longwall top coal mining. 

I hope the comments would help improve the quality of the manuscript. 

With kind regards.

Comments on the Quality of English Language

The quality of English is not satisfactory for publication. Please receive support in improving the quality of English. 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript proposes a partial paste backfill mining method suitable for Fully Mechanized Top-Coal Caving Face, which innovatively solves the problem of small filling space in Fully Mechanized Top-Coal Caving Face. This method can provide guidance and reference for thick coal seam filling mining, and has important theoretical and engineering significance. The overall evaluation of the manuscript suggests minor revisions. The review comments are as follows.

1. The meanings of C₁, C₂, C₃, and C₄ parameters are not given in formulas (5) and (6). It is suggested that the author add calculation formulas or determination methods for each parameter.

2. The author needs to add a flowchart of the filling process in the filling process section. This can increase readers' understanding of the filling process and increase the readability of the manuscript.

3. Most of the references are from two years ago. It is recommended that the author add the latest relevant references from the past year or two.

4.The author used numerical simulation to study the failure characteristics of overlying rocks. Suggest the author to provide a basis for the failure criteria of coal rock mass in this section.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

This paper presents a comprehensive case study on the application of the partial paste backfill mining method within a fully mechanized top-coal caving face in a coal mine in China. offer valuable insights into the evolution of overlying strata under various mining scenarios, including intermittent cut and fill, longwall excavation, and continuous fill. The study’s findings that intermittent filling and excavation can significantly minimize overburden damage and subsidence are particularly noteworthy and contribute meaningfully to the literature on sustainable mining practices.The manuscript is well organized, reasonable in structure, clear in thought and credible in conclusion.My detailed comments are as follows:

1.Abstract: It is necessary to summarize the main quantitative conclusions of this study, rather than just describing what this study has done.

2.Introduction : The authors provide a comprehensive overview of the Partial Paste Backfill Mining Method used in a fully mechanized top-coal caving face, with specific reference to a case study from a coal mine in China. However, it would greatly enhance the reader’s understanding if the authors could provide a brief comparison with other backfill mining methods, highlighting the unique aspects and advantages of the Partial Paste Backfill Mining Method.

3.Partial Filling Mining Method : . For further clarity, it is recommended that the authors include schematic diagrams or figures illustrating each step of the process. This would help readers visualize the method more effectively.

4.Results and Discussion on Overburden Movement: . It would be beneficial if the authors could expand this section by discussing the implications of these findings for mine safety and productivity.

5. It is mentioned that software was used for validation, yet there is minimal information on the specific software tools or the validation process itself. Providing details on the software used and explaining the validation methodology would bolster the credibility of the study’s results.

6.Figures: The article mentions figures (e.g., Figure 5 showing the relationship between superstratum stress and mining distance at different filling rates), but there is no direct critique here. Ensure that all figures and tables are clearly labeled and referenced within the text. The interpretation of images should not be limited to the explanation of phenomena, but should further analyze the underlying mechanisms.

7.Conclusion: Do not merely describe phenomena, but rather summarize the underlying principles behind the phenomena.

8.It would be beneficial for the authors to more explicitly state the novel contributions of their research to the existing body of knowledge, especially in the conclusion section, to highlight the significance of their work.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

The article contains interesting analytical solutions and numerical studies on the distribution of stresses and displacements around workings partially filled with paste backfill. The idea of the proposed solution is interesting both in scientific and technological terms and may be useful in improving the stability of the transport and ventilation roadways of the longwall face. Below are some comments and suggestions:

1. In the introduction, it is worth mentioning that one of the important parameters of paste backfill is its compressibility (doi:10.3390/en14227750), which, due to the different content of ingredients, mainly cement, affects the deformability of the overlying layers;

2. For Figure 1, for designation 1 - the name "chute" is not used; if it is an inclined working, it is better to use the name inclined roadway;

3. In the subsection 2.2.3, it should be expanded the information regarding the backfilling process, first of all, please write: what diameters of the pipelines are used to transport the backfill mixture to the post-mining space; how long the backfilling takes, in how many work shifts it is carried out and how many meters the pipeline is shortened - in other words, how long is the backfilling step;

4. In the subsection 3.2.1, a few sentences should be added regarding the control of the backfilling process; what criterion is adopted for the correct flow of the backfill mixture and the degree of filling of the goafs;

5. Line 302, word "lonngueur" - should be corrected;

6. In the fourth chapter, table 1 presents the parameters for backfill, but there is no information for goafs, so it is necessary to write what structural, strength and deformation parameters were adopted for goaf. In addition, please describe how the cohesive and internal friction angle parameters were determined - were they selected from the table and calculated on the basis of laboratory tests;

7. For Figure 6b, please explain what causes the increase-decrease-increase in vertical stress on the section from 60 m to 120 m in relation to a filling rate of 100% - please explain why such a fluctuation is not visible for the filling rate curve of 80%;

8. Line 473, Mpa unit;

9. Figures 13 and 14 - check the units MPa, GPa, GP;

10. In the subsection 5.3.2, it is worth adding information regarding the permissible value of deflection/displacement of the rock mass layers so that the results can be compared or it can be stated that the subsidence and inclinations have not been exceeded;

11. In the conclusions, please add one statement regarding the comparison of the progress between the progress of the longwall face with just the caving and the longwall face with the caving and partial backfilling - in other words, whether this type of liquidation of workings affects the effectiveness of the progress of mining works.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Dear authors, 

Thank you very much for revising the manuscript. The revisions are sufficient for publication in Sustainability. However you should include the 3D schematic diagram representing the backfill method in top coal mining. You may include the figure stated in the author's reply. 

Round 3

Reviewer 1 Report

Comments and Suggestions for Authors

Dear authors

Thank you very much for revising the manuscript.

It is fine now and can be accepted for publication in Sustainability.