Study on Instability Characteristics of the Directional Borehole on the Coal-Seam Roof: A Case Study of the Tingnan Coal Mine
Round 1
Reviewer 1 Report
processes-2371331-review
Study on instability characteristics of the directional borehole on the coal-seam roof: A case study of the Tingnan Coal Mine
In this paper, the geological conditions of the #4 coal seam in the Tingnan Coal Mine, Shaanxi Province, China was taken as the application background, and the deformation characteristics of boreholes under four typical coal and rock conditions were first analyzed based on the UDEC numerical simulation. Secondly, the stress, strain and plastic deformation of the rock surrounding the borehole with different diameters were carried out using FLAC 3D. This is an interesting and valuable topic. However, The current version of the manuscript has significant flaws, and detailed comments and suggestions are as follows:
(1) Lack of important geological background, engineering geological conditions, hydrogeological conditions, tectonics, stratigraphic lithology description, etc. The simulation without geological background is like playing a game.
(2) How does the authors consider the influence of crustal stress and tectonics on the structural stability of borehole.
(3) A complete directional drilling structure should be established in the numerical simulation.
(4) Why did you choose two numerical simulation software, UDEC and FLAC 3D.
(5) The discussion section is too simple. The analysis of the internal mechanisms of drilling deformation and stress evolution should be deepened.
(6) How the results of numerical simulation guide engineering practice.
(7) The results of numerical simulation should be supported by appropriate measured data.
(8) Can lines 431-433 be deleted. In addition, the language needs deep polish, and there are some syntax error. Figure 1 needs optimization.
(9) Some references may be helpful,
DOI: 10.1007/s10230-020-00701-x,
DOI: 10.1021/acsomega.2c06749,
DOI: 10.3390/w14244093,
DOI: 10.1016/j.jngse.2022.104766,
DOI: 10.1016/j.tust.2022.104701
(10) This is an interesting and valuable topic. However, the author's analysis is not in-depth enough and the key content is missing. Therefore, a significant amount of modification is required before re examination.
the language needs deep polish, and there are some syntax error
Author Response
Dear Editor and Reviewers:
Thanks for reviewers’ comments on our manuscript entitled “Study on instability
characteristics of the directional borehole on the coal-seam roof: A case study of the Tingnan Coal Mine” (ID: processes-2371331). Those comments are all valuable and very helpful for revising and improving our paper. We have read comments carefully and revised accordingly. The revised contents are marked in red in the manuscript. Below are the responds to the reviewers’ comments:
Responds to the reviewer’s comments:
Comment 1: Lack of important geological background, engineering geological
conditions, hydrogeological conditions, tectonics, stratigraphic lithology description, etc. The simulation without geological background is like playing a game.
Response: We sincerely appreciate for your valuable comment. We have added the geological description of the Tingnan coal mine in the manuscript in lines 168-196. And here we did not list the revision but marked in red in the manuscript. We earnestly hope the revision will meet with approval.
Comment 2: How does the authors consider the influence of crustal stress and
tectonics on the structural stability of borehole.
Response: Thanks for your valuable comment. In deep mine, the buried depth of
borehole (in-situ stress) and lateral pressure coefficient (tectonics) are one of the
important factors affecting the structural stability of borehole. With increasing burial
depth, the in-situ stress increases continuously, and the maximum vertical displacement, maximum horizontal displacement, and maximum vertical stress of the surrounding rock of the borehole obviously increase. The stability of the borehole decreases as the stress increases everywhere, so it is necessary to have support for the borehole. Due to different tectonics, the lateral pressure coefficient varies greatly. This has a large influence on the maximum vertical displacement and the maximum horizontal displacement, but little influence on the maximum vertical stress. Tectonics is a major determinant of in-situ stress distribution, so areas of anomalous geological structure should be avoided as much as possible during the drilling. However, considering that this research is based on Tingnan Coal Mine in Shaanxi Province, and the buried depth of the 208-working face in Tingnan Coal Mine is 430 meters; moreover, no major fault was found in the coal mine field, so the influence of in-situ stress and tectonics was not analyzed when studying the stability of the directional boreholes.
Comment 3: A complete directional drilling structure should be established in the
numerical simulation.
Response: Thanks for your valuable suggestion. We have added a complete coal seam
mining model of directional drilling structure as shown in Figure 1(a) in the Section
2.1.1 Model Building. The model is 300 meters long and 180 meters high. According to the histogram distribution of rock layers, joints are set and grids are divided, and the number of grids is 2976224. At the upper boundary of the model, the self-weight stress of the overlying strata is imposed, and the simulated mining depth is 430m. According to the actual situation, it is assumed that the left and right sides are mined together, and the distance between the mining boundary and the left and right boundaries of the model is 60 meters, each mining is 10 meters, and the mining length is 180 meters. To facilitate simulation and calculation, the model is partially simplified: The change in coal seam dip angle and thickness is ignored, and the calculation is based on the average coal seam thickness. Considering the large span of high-level directional drilling in horizontal and
vertical directions, the strata and rock lithology through which the drilling passes are also complicated. Therefore, this study models and analyzes the stability of high-level directional drilling under different lithologies based on mining disturbance. Considering the different lithologic horizons that are encountered in drilling practice, four main rock layers are selected for study in the model, namely coal rock, mudstone, fine-grained sandstone and coarse-grained sandstone. Given that the roof-directed long borehole has a large span in the roof, the horizon and rock lithology through which the hole passes is complex. The borehole stability of coal, mudstone, fine-grained sandstone and coarse-grained sandstone in the working face rock mass was investigated using the UDEC. A 1m×1m rock mass model with a 130mm aperture is created as shown in Figure 1(b) and Figure 1(c).
Comment 4: Why did you choose two numerical simulation software, UDEC and FLAC 3D.
Response: Thanks for your valuable question. We choose two numerical simulation software to integrate their advantages. UDEC has the advantages of fast modeling, high reproducibility and intuitive effect compared with similar simulation research. UDEC is commonly used to study rock instability in two dimensions. FLAC 3D can simulate the mechanical properties of three-dimensional structures of soil, rock and other materials and analyze plastic flow. FLAC 3D adopts explicit Lagrangian algorithm and mixed-discrete partition technology, which can accurately simulate plastic failure and flow. Since there is no need to form a stiffness matrix, a wide range of three-dimensional problems can be solved based on a small memory space.
Comment 5: The discussion section is too simple. The analysis of the internal
mechanisms of drilling deformation and stress evolution should be deepened.
Response: Thanks for your valuable suggestion. We have revised the discussion section in lines 419- 434. And here we did not list the revision but marked in red in the manuscript. We earnestly hope the revision will meet with approval.
Comment 6: How the results of numerical simulation guide engineering practice.
Response: Thanks for your valuable comment. We have added the guidance in the Section 4 to strengthen the analysis of the results. There are many factors that affect the stability of the borehole, and they can be roughly divided into two categories: geological factors and engineering factors. The geological factors include the in-situ stress, the geological structure, the mechanical properties of the coal and rock mass, the gas pressure, etc.; and the engineering factors include the drilling technology and the support methods. The simulation results show that the stability of high-level directional drilling is greatly affected by both lithology and aperture. The stability of the borehole is inversely proportional to the size of the borehole. As the borehole diameter increases, the stress distribution area, plastic zone and displacement around the borehole begin to increase significantly. When the borehole diameter exceeds 160mm, the borehole will be in a relatively unstable state, which may lead to instability and damage, and appropriate borehole protection measures should be taken. By analyzing the compression test structures of PVC borehole protection pipes with different internal support structures, it can be concluded that the compression resistance of 110 mm and
160 mm diameter borehole with the cross-shaped internal support structures is the best. Compared with ordinary borehole protection pipes with other internal support
structures, it is capable of providing stronger and more effective support. Therefore, the 110 mm diameter borehole with cross-shaped support structure can be selected for engineering field.
Comment 7: The results of numerical simulation should be supported by appropriate measured data.
Response: We sincerely appreciate for this excellent suggestion. Coal samples were taken from the No. 4 coal seam of the Tingnan Coal Mine, Xianyang, Shanxi Province, China. The sampling site was the 208-working face of the coal mine. Data of the rock mechanical parameters are obtained by the triaxial stress test in the laboratory, as shown in Table 1 in line 234.
Comment 8: Can lines 431-433 be deleted. In addition, the language needs deep polish, and there are some syntax errors. Figure 1 needs optimization.
Response: Thanks for your careful checks. We have deleted the lines 431-433. We have invited a friend of us who is a native English speaker from the Canada to help polish the language and writing style, the modifications of the language are marked in red in the manuscript. And we hope the revised manuscript could be acceptable for you. We have optimized and marked the size of the figure in line 232, page 7.
Comment 9: Some references may be helpful, DOI: 10.1007/s10230-020-00701-x,
DOI: 10.1021/acsomega.2c06749, DOI: 10.3390/w14244093, DOI:10.1016/j.jngse.2022.104766, DOI: 10.1016/j.tust.2022.104701.
Response: We sincerely appreciate for these excellent references. We have checked the literature carefully and added these important references into the literature review in lines 103-113.
Comment 10: This is an interesting and valuable topic. However, the author's analysis is not in-depth enough and the key content is missing. Therefore, a significant amount of modification is required before re-examination.
Response: Thanks for your valuable comment. We have read comments carefully and revised accordingly. We appreciate for your warm work earnestly and hope that the revised manuscript will meet with your approval.
Reviewer 2 Report
Comment 1. The paper is about studying the stability of the surrounding rock in directional long drilling on the roof, which is used as a gas control measure in the goaf. The study analyzes the deformation characteristics of boreholes under different coal and rock conditions and simulates the stress, strain, and plastic deformation of the rock surrounding the borehole with different diameters. The effect of casing on borehole stability is also simulated. The research found that the borehole stability of coal and mudstone was lower than that of fine-grained sandstone and coarse-grained sandstone, and the larger the borehole diameter, the lower the stability. The research also tested various internal support tubes and found that the cross-shaped pipe had the highest compressive strength and a good protective effect. The research results can provide technical support for the protection of directional boreholes on roofs through strata and have important implications for the popularization and application of the directional long borehole technique. The manuscript has practical implications as well as significant theoretical contributions for future research. Upon making the corrections outlined below, the paper may be considered for publication.
Comment 2. Lines 41-86 make one paragraph. Please subdivide it into several ones.
Comment 3. Lines 119-121. “This paper will provide some guidance for the popularization and application of directional long borehole on the roof technology, and also gradually realize the "replacing alley with borehole" in goaf gas treatment.” – Please add after this text the tasks of the research.
Comment 3. The paper's readability is challenging, and it would be helpful if the authors had structured it using the widely recognized IMRaD format. A traditional pattern, including clearly stated Methods, Results, and Discussion sections, would assist readers in grasping the manuscript's essential concepts.
Comment 4. In the Introduction section, an enhanced literature review is required. Why? Because for this study, the authors have used only literature sources from China.
Comment 5. Including a contextual explanation of why the study is significant would be beneficial for readers and enhance the paper's overall value.
Comment 6. What are the limitations of your research?
Comment 7. Please consider the suggested research in your paper when enhancing the literature review. I believe they are worth considering in your paper.
Katanov, Y.; Vaganov, Y.; Cheymetov, M. Neural simulation-based analysis of the well wall stability while productive seam penetrating. Min. Miner. Depos. 2021, 15, 91-98. https://doi.org/10.33271/mining15.04.091
Ma, Y.; Xu, Y. Research into technology for precision directional drilling of gas-drainage boreholes. Min. Miner. Depos, 2022, 16, 27-32. https://doi.org/10.33271/mining16.02.027
Comment 8. Please discuss mentioned below questions in the methodology section.
What geological conditions were used in the study (detailed)?
What method was used to analyze the deformation characteristics of boreholes?
How were the stress, strain, and plastic deformation of the rock surrounding the borehole measured?
What was the effect of casing on the stability of the borehole?
What types of internal support tubes were tested in the study, and what were the results?
Comment 9. What about the influence of geological disturbance on well stability? Can such actions make influence Damage Evolution Law? Please consider mentioned below research in your study as it can affect further research direction.
Dychkovskyi, R.O., Lozynskyi, V.H., Saik, P.B., Petlovanyi, M.V., Malanchuk, Ye.Z., & Malanchuk, Z.R. (2018). Modeling of the disjunctive geological fault influence on the exploitation wells stability during underground coal gasification. Arch. Civ. Mech. Eng. 2018, 18, 1183-1197. https://doi.org/10.1016/j.acme.2018.01.012
Petlovanyi, M.; Lozynskyi, V.; Saik, P.; Sai, K. Predicting the producing well stability in the place of its curving at the underground coal seams gasification. E3S Web of Conf. 2019, 123, 01019. https://doi.org/10.1051/e3sconf/201912301019
Comment 10. The references are presented not in MDPI style. You need to reformat existing references with a proper guide.
Comment 11. Address e a short description of further research.
Comment 12. In general, the presented article leaves a positive impression and, after eliminating these comments and taking into account the recommendations made, it can be recommended for publication in the journal “Processes”.
Author Response
Comment 1: The paper is about studying the stability of the surrounding rock in directional long drilling on the roof, which is used as a gas control measure in the goaf. The study analyzes the deformation characteristics of boreholes under different coal and rock conditions and simulates the stress, strain, and plastic deformation of the rock surrounding the borehole with different diameters. The effect of casing on borehole stability is also simulated. The research found that the borehole stability of coal and mudstone was lower than that of fine-grained sandstone and coarse-grained sandstone, and the larger the borehole diameter, the lower the stability. The research also tested various internal support tubes and found that the cross-shaped pipe had the highest compressive strength and a good protective effect. The research results can provide technical support for the protection of directional boreholes on roofs through strata and have important implications for the popularization and application of the directional long borehole technique. The manuscript has practical implications as well as significant theoretical contributions for future research. Upon making the corrections outlined below, the paper may be considered for publication.
Response: Thanks for your valuable comment. We have read comments carefully and revised accordingly. We appreciate for your warm work sincerely and hope that the revised manuscript will meet with your approval.
Comment 2: Lines 41-86 make one paragraph. Please subdivide it into several ones.
Response: Thanks for your valuable comment. We have subdivided the first paragraph in the introduction section into three ones in the manuscript.
Comment 3: Lines 119-121. “This paper will provide some guidance for the popularization and application of directional long borehole on the roof technology, and also gradually realize the "replacing alley with borehole" in goaf gas treatment.” – Please add after this text the tasks of the research.
Response: We think this is a valuable comment. We have added the tasks of this research in the manuscript in lines 152-158. The rest of this study is organized as follows. Section 2 analyzes the deformation characteristics of boreholes under different coal and rock conditions, and simulates the stress, strain and plastic deformation of rocks around boreholes with different diameters. In section 3, the experiment on the influence of internal support hole protection tube on the stability of hole wall was carried out. Section 4 analyzes the mechanism of numerical simulation and laboratory experiment results. Finally, the conclusions are presented in section 5.
Comment 3: The paper's readability is challenging, and it would be helpful if the authors had structured it using the widely recognized IMRaD format. A traditional pattern, including clearly stated Methods, Results, and Discussion sections, would assist readers in grasping the manuscript's essential concepts.
Response: We earnestly appreciate for the valuable comment. We have revised the manuscript in a traditional pattern to present a present our research and findings.
Comment 4: In the Introduction section, an enhanced literature review is required. Why? Because for this study, the authors have used only literature sources from China.
Response: Thanks for your valuable comment. We have revised the review of the literature in the Introduction section and have added some of the literature sources from around the world. And here we did not list the revision but marked in red in the manuscript. We earnestly hope the revision will meet with approval.
Comment 5: Including a contextual explanation of why the study is significant would be beneficial for readers and enhance the paper's overall value.
Response: Thanks for this valuable and significant comment. We have added the significance of this research in the Conclusions section. Borehole construction is the prerequisite for gas extraction in drilling. However, during the drilling construction, factors such as lateral pressure factor, mechanical strength of rock, confining pressure and so on are influenced, so that the drilling hole is easily deformed and collapsed, so that the drilling gas extraction performance is poor, and brings hidden hazards to the coal mine safety production. Research on the borehole collapsing law and corresponding borehole protection techniques has great practical significance for preventing the borehole distortion and collapsing, increasing the borehole stability, and improving the gas drainage.
Comment 6: What are the limitations of your research?
Response: We sincerely thank you for this valuable comment. We have revised the Conclusions Section of the research. And here is the limitation: The inner support structure borehole protection pipe is suitable for the high-level directional borehole protection. Improving the stability of the high-level directional borehole by the inner support structure borehole protection pipe is beneficial to the efficient gas drainage in the goaf, and can promote the popularization and application of the high-level directional borehole. However, the compressive experimental effect of the inner support structure borehole protection pipe may not be equal to the actual borehole protection effect in the field. Therefore, it is necessary to carry out systematic field experimental research in various mines in the future to further investigate its borehole protection effect. We earnestly hope this revision can meet with your approval.
Comment 7: Please consider the suggested research in your paper when enhancing the literature review. I believe they are worth considering in your paper.
Katanov, Y.; Vaganov, Y.; Cheymetov, M. Neural simulation-based analysis of the well wall stability while productive seam penetrating. Min. Miner. Depos. 2021, 15, 91-98. https://doi.org/10.33271/mining15.04.091; Ma, Y.; Xu, Y. Research into technology for precision directional drilling of gas-drainage boreholes. Min. Miner. Depos, 2022, 16, 27-32. https://doi.org/10.33271/mining16.02.027
Response: We sincerely appreciate for the recommendation of these significant literatures. We have enhanced the literature review through adding these two indispensable references in lines 76-81, page 2.
Comment 8: Please discuss mentioned below questions in the methodology section.
What geological conditions were used in the study (detailed)?
What method was used to analyze the deformation characteristics of boreholes?
How were the stress, strain, and plastic deformation of the rock surrounding the borehole measured?
What was the effect of casing on the stability of the borehole?
What types of internal support tubes were tested in the study, and what were the results?
Response: Thanks for your valuable suggestion. We have revised the methodology section in the manuscript. We earnestly hope this response can meet with your approval.
(1) We have added the geological conditions of the Tingnan coal mine in lines - .
(2) Through the radial compression experiment on the GCTS rock mechanics test system, the compression resistance of PVC pipes with different diameters is studied, because radial compression is the main failure mode of well casing. According to the data recorded in the experiment, such as load and displacement, after processing, the compression resistance of the casing and the stability of the borehole can be analyzed.
(3) The compression tests on boreholes of various diameters under various loads and on borehole protection pipes with internal support structures were conducted in the Section 3. The compression tests did not measure the stress, strain and plastic deformation of the rocks around the boreholes.
(4) According to the results of physical simulation experiment, whether there is casing or not has a great influence on the deformation of borehole; When the construction in the field, especially in deep coal seam, the drilling is easy to lose stability, so it is necessary to use casing to support the boreholes.
(5) To strengthen the borehole protection effect, this study designed three types of hole protection pipes with internal support structures: 'line-shaped', 'Y-shaped', and 'cross-shaped'; and verified their hole protection effects by compression experiments. The experimental results show that the cross-shaped internal supporting structure has the best compressive performance and can provide a better borehole protecting support.
Comment 9: What about the influence of geological disturbance on well stability? Can such actions make influence Damage Evolution Law? Please consider mentioned below research in your study as it can affect further research direction. Dychkovskyi, R.O., Lozynskyi, V.H., Saik, P.B., Petlovanyi, M.V., Malanchuk, Ye.Z., & Malanchuk, Z.R. (2018). Modeling of the disjunctive geological fault influence on the exploitation wells stability during underground coal gasification. Arch. Civ. Mech. Eng. 2018, 18, 1183-1197. https://doi.org/10.1016/j.acme.2018.01.012; Petlovanyi, M.; Lozynskyi, V.; Saik, P.; Sai, K. Predicting the producing well stability in the place of its curving at the underground coal seams gasification. E3S Web of Conf. 2019, 123, 01019. https://doi.org/10.1051/e3sconf/201912301019
Response: Thanks for your valuable comment. We have revised the manuscript in view of these important references in the literature review in lines 81-89, page 2. There are many factors that affect borehole stability, which can be roughly divided into two categories: geological factors and engineering factors. Geological factors include in-situ stress, geological structure, mechanical properties of coal and rock mass, gas pressure, etc., and engineering factors include drilling technology and support methods. In deep mine, the buried depth of borehole (in-situ stress) and lateral pressure coefficient (tectonics) are one of the important factors affecting the structural stability of borehole. With increasing burial depth, the in-situ stress increases continuously, and the maximum vertical displacement, maximum horizontal displacement, and maximum vertical stress of the surrounding rock of the borehole obviously increase. The stability of the borehole decreases as the stress increases everywhere, so it is necessary to have support for the borehole. Due to different tectonics, the lateral pressure coefficient varies greatly. This has a large influence on the maximum vertical displacement and the maximum horizontal displacement, but little influence on the maximum vertical stress. Tectonics is a major determinant of in-situ stress distribution, so areas of anomalous geological structure should be avoided as much as possible during the drilling. However, considering that this research is based on the Tingnan Coal Mine in Shaanxi Province, and the buried depth of the 208-working face in the Tingnan Coal Mine is 430 meters; moreover, no major fault was found in the coal mine field, so the influence of in-situ stress and tectonics was not analyzed when studying the stability of the directional boreholes.
Comment 10: The references are presented not in MDPI style. You need to reformat existing references with a proper guide.
Response: We were really sorry for our careless mistakes. Thank you for your valuable reminder. We have reformatted the references in MDPI style according to the Microsoft Word Templates are available on the Processes journals' Instructions for Authors pages, which is believed to be in line with the journal style.
Comment 11: Address e a short description of further research.
Response: Thanks for your valuable comment. Here is our further research. We have added the description of further research in the Conclusions Section. In this study, some works were made on the stability and borehole protection technology of the directional borehole by numerical simulation and experiment, but there are still some deficiencies which need strengthening and improvement, such as the following:
(1) Due to the limited computing power, the numerical simulation is mainly based on two-dimensional simulation, and many simplifications were made. A closer combination of drilling and mining should be considered for analysis in the future.
(2) The production cost of the internal support hole protection pipe is higher than that of the common hole protection pipe. The further research should improve and reduce the cost, so as to facilitate the subsequent popularization and application.
Comment 12: In general, the presented article leaves a positive impression and, after
eliminating these comments and taking into account the recommendations made, it can
be recommended for publication in the journal “Processes”.
Response: Thanks for your supporting comment. We have read comments carefully and
revised accordingly. We appreciate for your warm work earnestly and hope that the
revised manuscript will meet with your approval.
Reviewer 3 Report
Please see the attached comments.
Comments for author File: 
Comments.pdf
Some grammatical errors are found, please improve the English writing.
Author Response
Comment 1: Please avoid using abbreviation in the abstract.
Response: We were really sorry for our careless mistakes. Thank you for your valuable reminder. We have revised the abbreviation (eg. “UDEC” and “FLAC 3D”) in the abstract in line 23 and 25, page 1.
Comment 2: Please show the structure of this work at the end of the Introduction.
Response: Thanks for your valuable comment. We have added the brief structure at the end of the Introduction section after line 152. The rest of this study is organized as follows. Section 2 analyzes the deformation characteristics of boreholes under different coal and rock conditions, and simulates the stress, strain and plastic deformation of rocks around boreholes with different diameters. In section 3, the experiment on the influence of internal support hole protection tube on the stability of hole wall was carried out. Section 4 analyzes the mechanism of numerical simulation and laboratory experiment results. Finally, the conclusions are presented in section 5.
Comment 3: Please mark the size of the numerical model in Fig. 1.
Response: We sincerely appreciate for this suggestion. We have optimized and marked the size of the numerical model in Figure 1(b) and Figure 1(c) in the manuscript.
Comment 4: The literature review is incomplete. More studies regarding coal seam development can be found:
1) Petroleum rock mechanics: An area worthy of focus in geo-energy research.
2) A semi-analytical model for the transient pressure behaviors of a multiple fractured well in a coal seam gas reservoir.
3) Longwall mining automation horizon control: Coal seam gradient identification using piecewise linear fitting.
Response: We sincerely appreciate for the recommendation of these significant literatures. We have enhanced the literature review in view of these important references in lines 65-66,page 2; and lines 113-117, page 3. We earnestly hope this revision will meet with your approval
Comment 5: How did authors determine the values of these parameters shown in Table 1?
Response: We sincerely thank for your valuable comment. Coal samples were taken from the No. 4 coal seam of the Tingnan Coal Mine, Xianyang, Shanxi Province, China. The sampling site was the 208-working face of the coal mine. Data of the rock mechanical parameters are obtained by the triaxial stress test in the laboratory, as shown in Table 1.
Comment 6: Please improve the quality of Figs, 4 and 5, the current one is hard to understand.
Response: We sincerely appreciate for this valuable suggestion. We have enhanced the quality of Figures, 4 and 5 present a better understanding effect. And these enhanced figures also could be found in the supplementary materials of figures.
Comment 7: The Conclusions need a better flow to highlight the novelties and findings of this work.
Response: Thanks for your valuable comment. We have revised the Conclusions
section to present the novelties and findings of this work. We earnestly hope this revision will be able to meet with your approval.
Reviewer 4 Report
In general, the drawings are too small and readability suffers.
Figure 17 and its description must be complementary - a correction is necessary.
Comments for author File: Comments.pdf
Minor errors were highlighted in grey in the attached paper.
Author Response
Comment 1: In general, the drawings are too small and readability suffers.
Response: Thanks for your valuable comment. We have revised the shape and quality of the drawings to present a better readability effect. We hope the revised drawings could be acceptable for you.
Comment 2: Figure 17 and its description must be complementary - a correction is necessary.
Response: We sincerely appreciate for your valuable comment. We have added the description of the Figure 17. And here is the description: The system is a hydraulic servo-mechanical system produced by GCTS Company in the United States, which meets the requirements of ISRM triaxial rock test of the International Society of Rock Mechanics and the American standard ASTM D2664-04. It is mainly used to test the mechanical properties and seepage characteristics of rock, concrete and coal under
complex loading conditions. The test accuracy is high and the performance is stable.
Comment 3: Minor errors were highlighted in grey in the attached paper.
Response: Thanks for your valuable and meticulous comment. We have revised the errors were highlighted in grey according to your instruction. We sincerely appreciate for your warm work and hope that the revised manuscript will meet with your approval
Round 2
Reviewer 1 Report
can be accepted
Moderate editing of English language
Reviewer 2 Report
Perfect.
You have done a great revision.
Please accept my congratulations.
Reviewer 3 Report
Authors have addressed all the issues, so the manuscript is acceptable.
