Experimental Study on Electric Potential Response Characteristics of Gas-Bearing Coal During Deformation and Fracturing Process
Round 1
Reviewer 1 Report
The paper entitled "Experimental Study on Electric Potential Response Characteristics of Gas-Bearing Coal During Deformation and Fracturing Process" is a good and interesting research, based on the results of laboratory tests on the generation of electrical potential (EP) when coal mass is deformed and fractured under stress.
- The paper can be published after some corrections.
- Page 2, line 67: “Takeuchi et al. [22-23]” is better “Takeuchi et al. [22] and Wang et al. [23]”.
- Page 2, line 75: “Niu et al. [26]” it must be corrected in “Niuet al. [25]”.
- Page 2: Where is [26]?
- On the x-axis of the Figure 10 write: “Time (s)”.
- On the y-axis of the Figure 11, on the right and on the left, it is better to write the captions.
- In the References are absent: Guangzhi et al. (2018) [Pag 13, line 328], Polesek – Karczewska (2017) [Pag 14, line 360], Dokukin et al., (2009) [Pag 15, line 388] and He et al. (2018) [Pag 15, line 389].
- Page 18, line 466: In the References is absent [39].
- Page 13, line 330 to 333: There is no symbol “p” and its explanation. The connection of the symbols to the relative explanation is not very clear.
Author Response
Response to reviewer #1
In accordance with the comments of the reviewer #2, we have finished the following revisions:
Reviewer #2 pointed out:
The paper entitled "Experimental Study on Electric Potential Response Characteristics of Gas-Bearing Coal During Deformation and Fracturing Process" is a good and interesting research, based on the results of laboratory tests on the generation of electrical potential (EP) when coal mass is deformed and fractured under stress.
The paper can be published after some corrections.
Response: Thanks sincerely for your comments which are very helpful for revising and improving our manuscript. We have read the comments carefully which is valuable to improve the manuscript in-depth. Here we will make a further detailed reply to each comment.
Details are as follows:
1. Page 2, line 67: “Takeuchi et al. [22-23]” is better “Takeuchi et al. [22] and Wang et al. [23]”
Response: Thank you for your suggestion. “Takeuchi et al. [22] and Wang et al. [23]” has been replaced by “Takeuchi et al. [22-23]” in the revised manuscript.
2. Page 2, line 75: “Niu et al. [26]” it must be corrected in “Niuet al. [25]”.
Response: We are so sorry to miss an important reference as follows, which should be marked as [25].
Li, Z.H.; Wang, E.Y.; He, X.Q. Study on theory and mechanism of surface potential during coal fracture. Xuzhou, China University of Mining and Technology Press, 2013.
After the correction, “Niu et al. [26]” is available in the manuscript. Thank you for consideration.
3. Page 2: Where is [26]?
Response: After adding the reference [25], the [26] is not missed. We are so sorry for the mistake.
4. On the x-axis of the Figure 10 write: “Time (s)”.FDSAA
Response: Thank you very much. It is our carelessness for this mistake. We have corrected the item.
5. On the y-axis of the Figure 11, on the right and on the left, it is better to write the captions.
Response: Thank you for your valuable suggestion. Figure 11 describes the change of broken strength, strain maximum, EP maximum, EP variation coefficient along with loading time separately. It indicates the mechanics properties and EP response impacted the gas pressure. We have add the legends and revised the graphs. Hope it will meet your requirements.
6. In the References are absent: Guangzhi et al. (2018) [Pag 13, line 328], Polesek – Karczewska (2017) [Pag 14, line 360], Dokukin et al., (2009) [Pag 15, line 388] and He et al. (2018) [Pag 15, line 389].
Response: We are so sorry for the missed marks in the references. We have corrected the mistakes. The four references have been added and the order also was adjusted.
7. Page 18, line 466: In the References is absent [39].
Response: The reference has been added in References section.
8.Page 13, line 330 to 333: There is no symbol “p” and its explanation. The connection of the symbols to the relative explanation is not very clear.
Response: We are so sorry that “p” is equal to “P”, which means the gas pressure. We will correct the equation in the revised manuscript. Thanks so much for your carefulness.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Dear Authors,
Many thanks for your good work with the title of "Experimental Study on Electric Potential Response Characteristics of Gas-Bearing Coal During Deformation and Fracturing Process". I can see that your paper has almost a good structure but it suffers from many aspects and even some fundamental ones. Please find the following comments on your work.
1- First of all, all abbreviations must be defined before their first use. I can see that ER is never defined. Please revise your paper and fix these kind off errors.
2- As far as I see there is no novelty in your work. What is your novelty and what you have done new in this topic.
3- I can see that you claimed that you validated results and even mentioned it in abstract but i couldn't see any validation in your manuscript.
4- Your writing suffers from many grammatical mistakes and typos please revise it with the passive voice rather that using we or .....
5- When you define your experiment apparatus please put all the parts in a table to make it more readable for readers instead of using them in figure captions. Your figure capture is boring and it is too much.
6- What is your experimental errors? please define them all.
Author Response
Response to reviewer #2
In accordance with the comments of the reviewer #2, we have finished the following revisions:
Reviewer #2 pointed out:
Many thanks for your good work with the title of "Experimental Study on Electric Potential Response Characteristics of Gas-Bearing Coal During Deformation and Fracturing Process". I can see that your paper has almost a good structure but it suffers from many aspects and even some fundamental ones. Please find the following comments on your work.
Response: Thanks sincerely for your comments which are very helpful for revising and improving our manuscript. We have read the comments carefully which is valuable to improve the manuscript in-depth. Here we will make a further detailed reply to each comment.
Details are as follows:
1- First of all, all abbreviations must be defined before their first use. I can see that ER is never defined. Please revise your paper and fix these kind off errors.
Response: Thank you for the comments. The items have been corrected in the manuscript.
2- As far as I see there is no novelty in your work. What is your novelty and what you have done new in this topic.
Response: Previous studies have shown that granite, shale, coal, etc. can generate potential signals under the action of stress. Meanwhile, the EP response is closely related to the stress level and damage state of the material. As the current coal mining activities continue to deepen underground, the gas has a profound impact on the mechanical properties of coal and the evolution of damage. However, the predecessors have little research on the charging phenomenon of coal bodies under gas-bearing conditions, and have not formed a relatively complete research system.
The innovation of this paper is to design a multi-parameter experimental system for self-design, which is applied to test the dynamic evolution image of potential, acoustic emission signal and crack propagation during the loading process. Through the comparison of various indexes and the experimental results under different gas pressures, the EP response characteristics under stress and gas coupling are studied, and the physical mechanism of the generation was analyzed. The results show that in the process of deformation and failure on coal sample caused by stress and gas, the potential signal can also be generated, and the gas has confining pressure and erosion effect on the coal body. As results, the EP response is promoted by the influence of coal damage evolution. .
When the failure of the coal occurred, EP value rapidly rose to a maximum, which could be considered as anomalous information for monitoring the stability and revealing failure of gas-bearing coal. The research results are beneficial for further investigating the damage-evolution process of gas-bearing coal.
3- I can see that you claimed that you validated results and even mentioned it in abstract but i couldn't see any validation in your manuscript.
Response: We are sorry that limited with the abstract’s length, the verification has not been spread in details.
In the manuscript, as the loading progresses, the loading stress rises (Figure 5), the coal damage increases, the EP signals (Figure 8) and the AE signals (Figure 6) continue to increase, and the cracks continue to generate and expand (Figure 7). When the stress drop occurs, the EP intensity and AE count have the sudden increase in mutation. The AE count represents the number of micro-fractures inside the coal body. The average amplitude of the signal represents the intensity of the fracture. When the count is abrupt and the amplitude increases, it means that the damage of the coal body is more severe, meanwhile the EP is also abrupt. And the cracks expand significantly. When the coal body is unstable and to be ruptured, the AE count reaches the peak value, and the crack rapidly expands and penetrates, causing the fracture of the specimen. At this time, the potential intensity also rapidly reaches the peak value, which can be used as the monitoring abnormal information of the loading stress level and damage state of the coal body.
Besides, microscopically, comparing the SEM images before and after the coal body damage (Figure 12 and 13), it can be found that a large number of crack initiation and expansion occurred during the destruction of the specimen, resulting in structural damage of the specimen. This is the direct cause of the final failure of the specimen. In addition, many of the contents of the abstract can be verified from experimental results and theoretical analysis. Compared to the abstract, the conclusions in the conclusion are more detailed and specific.
4- Your writing suffers from many grammatical mistakes and typos please revise it with the passive voice rather that using we or .....
Response: Thank you for your comments. The grammatical mistakes and typos has been revised with the help of native English speaker scholar related to the research direction. Of course, the passive voice has been utilized as the help in the revised manuscript.
5- When you define your experiment apparatus please put all the parts in a table to make it more readable for readers instead of using them in figure captions. Your figure capture is boring and it is too much.
Response: Thank you so much for the good suggestion. The parts’ names and their number have been put in the new table separately to make it clear and more readable.
6- What is your experimental errors? please define them all.
Response: I am sorry might I misunderstand what you have introduced. Do you mean the accuracy of instruments which cause the experimental errors? If so, the answers are shown as follows.
The maximum load of loading system is 3000 kN and its accuracy can get the 10 N response if the load is less than 100 kN. The unpolarized electrode is adopted in the EP monitoring subsystem, and its drifting EP difference is less than 0.5 mV within 24 hours. During each experimental period, the EP value without loading can be considered as stable. Besides, the tightness of the sealed chamber is fine. The gas pressure can be kept as 2 MPa with loss less than 0.05 MPa for 24 hours. During the test, when the pencil lead is broken slightly, the AE sensor can counts less than 10 with the maximum energy values below 5 mV. It indicate the AE monitoring subsystem can reduce the environmental noise interference to low level, meeting the requirements of rock mechanics analyses.
If you have any other questions, please do not hesitate to contact us.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
Dear Authors,
Many thanks for providing the revised version of your manuscript with the title of "Experimental Study on Electric Potential Response Characteristics of Gas-Bearing Coal During Deformation and Fracturing Process". I think now your paper has a better quality and it has been improved a lot. I can see that you added and modified some table and some words to fulfill the reviewer comments. Apart from all of the corrections and improvement that you have done, I believe that the nomenclature still is not appropriate, it needs to be alphabetically corrected and moreover, you should separate greek alphabet.
Author Response
Response to reviewer #2 for second round
In accordance with the comments of the reviewer #2 for second round, we have finished the following revisions:
Reviewer #2 pointed out:
Many thanks for providing the revised version of your manuscript with the title of "Experimental Study on Electric Potential Response Characteristics of Gas-Bearing Coal During Deformation and Fracturing Process". I think now your paper has a better quality and it has been improved a lot. I can see that you added and modified some table and some words to fulfill the reviewer comments. Apart from all of the corrections and improvement that you have done, I believe that the nomenclature still is not appropriate, it needs to be alphabetically corrected and moreover, you should separate greek alphabet.
Response: Thanks sincerely for your recognition and encouragement on our revised manuscript. After consideration, your comment is valuable for the further improvement of the quality. We have do the following revision:
(1) Some inappropriate nomenclatures have been edited referencing others’ literature.
(2) All the symbols in the table are corrected alphabetically with the greek alphabet separated.
What we corrected has been marked red in the revision manuscript.
Thank you very much again for your time and patience.
Sincerely yours,
Zhonghui Li
Author Response File: Author Response.docx
