The Preparation of Active Support-Based Sealing Material and Sealing Effect Analysis

Round 1

Reviewer 1 Report

I am glad to read such a clear work and such an effective innovative method. The future and safety of underground coal mining can be assured with such remarkable results. I congratulate you on your efforts, concerns and results. Considering the value of the work as well as the clarity of the way of presentation, I opted for the publication of the work in its current form.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The authors discussed the development of a substrate-based sealing material and the analysis of the sealing effect. Researchers conducted orthogonal tests to investigate the design of the mixing ratio of sealing materials. They found that the best ratio of water to binder was: 0.9:1, quicklime content: 0.2, fly ash content: 0.3, accelerator content: 0.15, blowing agent content: 0.2. The work rightly states that with the increase of the active support force provided by the sealing material, the radius of the plastic zone and the fracture zone decrease respectively; the displacement around the borehole also shows a similar trend of change.

The work is very well developed both in terms of content and empirically. I do not make any negative remarks and request that the article be accepted for publication.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

REVIEWER’S COMMENTS (applsci-2425178)

The study uses a specifically designed active support testing device to analyze the development law of borehole fracture under the action of active support force, which was then verified by a field test in a mine in Henan Province. The manuscript needs a minor revision for it to be accepted for publication.

1. Lines 28-30: The authors reported gas drainage concentration unit as a percentage (47.5%) as shown in: ‘As has been proved by the engineering practice, under the same conditions, the gas drainage concentration of the new sealing material is 47.5%, which is 84.8% higher than that of the original sealing material.’ Why not use ppm (parts-per-million)?

2. Line 31: Add ‘borehole sealing’ to your keywords.

3. Lines 38, 43 and 57: The authors should avoid the use of lumped-up references such as [4-7].

4. Lines 54-55: The authors should cite a reference to support this statement: ‘Cement-based material is cheap and can be adjusted by adding additives, so it is widely used in borehole sealing. ’

5. Line 86: The authors should indicate the name of the accelerating agent used.

6. Line 98: What is the expanding agent used in the research? It should be stated in the study.

7. Figure 13: Why is the gas density measured in /%?

8. Lines 109-112: The authors should state the mechanism that led to this reported result: ‘According to the comprehensive analysis based on the orthogonal test of the borehole sealing material in Figure 4(a), the bleeding rate and initial setting time increase with the increase of the water-cement ratio, while the expansion rate and compressive strength decrease with the increase of the water-cement ratio.’

9. Figure 4: The graphs presented in this Figure seem unclear regarding the units of the parameters used in plotting the graphs. There is a lack of uniformity of units since compressive strength has different units of measurement with expansion rate or bleeding rate. The authors need to clarify this.

10. Lines 181-183: The authors need to reference this statement: ‘This is because the larger the expansion rate of the specimen is, the more pores there are in the specimen, and the higher the compaction degree would be under tri-axial compression.’

11. Figure 6: The authors should clarify the vertical axis labelling. Why use σ₁ -σ₃ on the vertical axis instead of σ?

12. Figure 6: The unit of σ₁ -σ₃ is MPa and not /MPa. The authors should change σ₁ -σ₃/MPa to  σ₁ -σ₃ (MPa). The same changes should be made for other Figures units.

The Quality of the English Language is good but can be improved using Grammarly software.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 4 Report

The authors have presented an experimental research study. Following comments should be considered before the acceptance:

1.      Triaxial tests are carried out on the specimens with the expansion rate of 0%, 1%, 3% and 5% respectively, and the loaded confining pressure grade gradient is 1MPa, 2MPa, and 3MPa. Three tests are conducted for each group of specimens, with a total sample size of 36 specimens. The confining pressure is loaded at a rate of 0.01MPa/s until it reaches the set value and then remains unchanged.

Justify this range of rate loading?

2.      At a confining pressure of 3MPa, the elastic modulus of the specimen with an expansion rate of 0% reaches 12.74GPa, 38.6% higher than that of uniaxial compression. 5% reaches 1.53GPa, 50% higher than that of uniaxial compression. By contrast, the increase amplitude is greater than that of 0%. The gas drainage concentration is increased by 84.8%. When the drainage lasts for 90 days, the gas drainage concentration with the bag-type borehole sealing device is 47.5%, increasing by 84.8%.

Poisson's ratio displays a downward trend with the increase of the expansion rate. With the increase of the expansion rate, the cohesion and internal friction Angle of the specimens decrease.

Authors should mention some comparative results in the literature review.

3.      This study revealed the effects of water-cement ratio, quicklime content, fly ash content, accelerating agent content and expanding agent content on the bleeding rate, fluidity, initial setting time, compressive strength, and expansion rate of the sealing material.

Authors should mention some comparative results in the literature review.

4.      With the increase of active support force provided by the sealing material, the radius of plastic zone and breakage zone decreases; the displacement around the borehole displays a similar changing trend.

Authors should mention some comparative results in the literature review.

5.      Based on the concept of active support sealing of gas drainage boreholes, the sealing material should possess the following characteristics: permeability, fluidity, expansibility, early strength, and compressive resistance. The test contents include material mobility, bleeding rate, initial setting time, expansion rate and compressive strength.

The authors should present justification about the choice of the studied combination of raw material.

6.      According to the comprehensive analysis based on the orthogonal test of the borehole sealing material, the bleeding rate and initial setting time increase with the increase of the water-cement ratio, while the expansion rate and compressive strength decrease with the increase of the water-cement ratio. When the quicklime content is 0.2, the sealing material performs better in terms of initial setting time, compressive strength, bleeding rate and expansion rate. With the increase of accelerating agent content, the bleeding rate and initial setting time decrease significantly.

Authors should compare their results with other researchers’ findings in the literature.

Originality of the study and the experimental work should be defended by a strong analysis of the results and specially with previous studies.

 The paper needs an overall review of English language, few points have been highlighted in attached pdf.

Comments for author File: Comments.pdf

Overall scientific writing seems fine, few grammatical errors have bben pointed out in attached pdf.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 5 Report

I have read the manuscript. The title is too wide since the is no materials or method used is mentioned. 

Moderate grammar edition is required. 

Problem statement and method is not clear in abstract. Plus, research gap or novelty is not mentioned.

Introduction can be improvised. The author is suggested to touch more on the method and materials used referring on the previous study. 

The author is suggested to remove Figure 2 and detailed up on the materials used. eg supplier or properties.

What kind or accelerating and expanding agent used in the experiment?

The test scheme should be elaborated in the paragraph. 

How is the author calculate the 16 groups of test?

The result, discussion and conclusion is well presented 

The author is suggested to do an moderate grammar edition as in this current form, the reading is still having grammatical and spelling error.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 4 Report

Dear authors thank you for considering the comments, however, the reviewers comments have not been properly taken into account and the actions are not reflected into the revised manuscript. Please take into consideration all the comments and reflect all the changes in the revised manuscript with page numbers. for-example the reply to comment number 2 is not satisfactory, authors need to compare the results in the light of already published literature and make the analysis and discussion more scientifically stronger.

"Answer: Thank you very much for your suggestion. The comparison of different materials is the direction we will take in our future studies. This article focuses on the analysis of the effect of expansion rate variation on the performance of the self-developed sealing material using different raw materials selected through orthogonal experiments. The conclusions are based on test results of the performance experiments of the self-developed sealing material."

Therefore, the authors are requested to consider the original comments again and please revise the manuscript accordingly. 

The scientific writing needs little improvement.

Author Response

Please see the attachment

Author Response File: Author Response.docx