Research on Subsidence Prediction Method of Water-Conducting Fracture Zone of Overlying Strata in Coal Mine Based on Grey Theory Model
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe development height and settlement prediction of water-conducting fracture zone caused by coal seam mining play an important role in the stability of overburden aquifer and the safety of roadway. This manuscript presented a prediction model of mining overburden subsidence based on measured vertical strain, and the optimal prediction method of the settlement of the water-conducting fracture zone was discussed. This manuscript is interesting. However, after reviewing the manuscript carefully, there are some deficiencies which need to be checked. Some suggestions listed below for modification.
1. In Introduction, the content of the second paragraph has little relationship on the topic of this manuscript. Some words should be given in the end of this paragraph to state the relationship and make the transition of the second and third paragraphs more naturally.
2. In Section 2, are there some new theory or method presented here, if it has, it is recommended to highlight the new theory or method. As well as, the theories put forward by the other scholars should be given the references more detailedly.
3. In Table 2, the last column “proportion number” should give the proportion materials names.
4. In Section 3.1, the similarity principle for determining the stress similarity ratio of 150 should be described in detail.
5. The numbers of decimal digits in Table 3 and in the text are not unified, they should be unified.
6. In Figure 4, why as the number of predictions increases, the prediction residuals of the three models gradually increase correspondingly, and the prediction accuracy decreases significantly should be explained in detail.
7. The axis name in the figures should not be italic, and please just let the variables to be italic.
8. Line 288-289, it stated “For the metabolic model, when the number of training and prediction times is before (7, 6), the accuracy level of the model is 1, and the accuracy gradually decreases as the number of tests increases.” Why the accuracy gradually decreases as the number of tests increases should be explained in detail.
9. The differences of the three kinds of models should be discussed and to explain the various trends of the curves in Figures 5 and 6.
10. A short statement on the application of this study is suggested to be added in the end of Section 4, with the propose of improving the engineering meaning of the study.
11. Line 330, the sentence “In summary, the following conclusions can be drawn.” has no meaning, it should be deleted.
12. There are some details that should be modified. Such as, typos: Line 97, “k=n” should be “k=n (italic)”; Line 133, r in Eq.5 should be italic; Line 153, (6) should be in the previous line; Line 136, these two formulas should be numbered. Please check the whole manuscript and modify them.
Comments on the Quality of English LanguageThe quality of English language is fine, just some typos should be checked more carefully.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsBased on the engineering geological data of J60 borehole in Daliuta Coal Mine, China, this study made a similar material test model of mining overburden. The deformation characteristics of overlying strata in the mining process of 2-2 coal seam were studied by using distributed optical fiber sensing technology, and the development height of water flowing fractured zone was determined. According to the equidistant sampling characteristics of Brillouin optical time do main reflection technology and GM (1, 1) model, this study established a prediction model of mining overburden subsidence based on measured vertical strain. Combined with the grey progressive model and the metabolic model, the optimal prediction method of the settlement of the water-con- ducting fracture zone was discussed.
The overall test is rigorous, and the result analysis is more accurate, but the article mainly has the following problems, and it is recommended to modify. After reexamination, the employment was arranged after checking that there was no error.
1、Page 3，It can be seen from the formula (2) that the trend of data transformation in the GM (1, 1) model may change over time, resulting in a decrease in the confidence of long-term prediction results.The trend of data transformation refers to the overall trend of the original data after the transformation of the GM model. This trend can be rising, falling or stable. How to change should be specified, not ambiguous.
2、Before coal seam mining, it is necessary to collect and analyze geological landform and mine engineering data. In this paper, the introduction of Daliuta Coal Mine lacks this part of the content needs to be supplemented.
3、Page 7,In this experiment, the development height of the water-conducting fracture zone is 37.8cm, which is basically consistent with the measured height of 37cm by photogrammetry. Combined with the actual observation on site, it should be explained whether the error is within the allowable range of the project.
4、Page 8, Table 3 Header A single English word is best not to change lines, to improve the convenience of reading.
5、Page 10, Figure 6 The last sentence of the first paragraph ' When the number of predictions is greater than 5, the model correlation degree is 1 level, and the number of predictions is less than 5. ' semantic logic has problems, not finished.
6、The prediction model is suitable for each stage of the settlement of the water-conducting fracture zone.
7、Grey theory assumes that the relationship between data is linear or exponential. If the actual data has a nonlinear relationship, the fitting effect of the grey model may be poor, and it will have a certain impact on the final prediction results.
8、In the process of coal seam mining, the deformation process of overlying strata has the characteristics of time-varying and non-linearity. The sensing cable is affected by complex external factors. Whether it is necessary to consider the influence of external factors on the prediction model and conduct more in-depth research.
9、Similar model has boundary effect in the process of simulating coal seam mining, which will bring adverse effects. In order to reduce the adverse effects of boundary effects, researchers usually need to introduce appropriate control and correction methods in research design and data processing to ensure the accuracy and reliability of research. The impact of the boundary effect is not considered in this paper, which will have a certain impact on the final prediction results.
10、The thickness and distribution of the aquifer will affect the development height of the water-conducting fracture zone. The change of groundwater level and groundwater extraction activity may also affect the development height of water flowing fractured zone. The impact on groundwater is not mentioned in this paper.
11、Whether a schematic diagram can be provided for the size of the similar material model and the layout of the sensing fiber for the reader to understand.
12、The development height of water flowing fractured zone is closely related to the distribution of aquifer, and is also affected by geological structure, rock properties, groundwater level and human activities. In hydrogeological survey and engineering survey, whether these factors need to be considered in order to more accurately understand the characteristics and distribution of water flowing fractured zone.
13、The change of temperature and humidity in coal seam may affect the refractive index of optical fiber, thus affecting the accuracy of measurement. Whether this effect needs to be considered or corrected in this study.
14、This article has fewer references to the literature in the past two years, and should increase the literature published in the past three years to enhance the timeliness and research novelty of the article.
15 In this paper, distributed optical fiber sensing technology is used to test the deformation and settlement of mining overburden. What are the advantages of distributed optical fiber sensing technology in overburden deformation monitoring? How to evaluate the accuracy of settlement calculation?
16 Both the grey progressive model and the metabolic model can supplement the new prediction sequence. From Figure 5 and Figure 6, it can be seen that the prediction accuracy of the data has a large deviation, and analyze the reasons.
17 In this paper, the sensing fiber is embedded into the rock and soil to monitor the deformation of the rock layer. What is the basis for the evaluation of the coupling between the two? The development height of water-conducting fracture zone is an important basis for evaluating water inrush from overlying strata in coal mines. How to distinguish it by using distributed optical fiber technology?
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThis article studies a prediction model of mining overburden subsidence based on measured vertical strain. The paper discussed a combined grey progressive model and the metabolic model, and the optimal prediction method for the settlement of the water-conducting fracture zone. The overall paper is interesting and relevant, however, some major review comments should be addressed before acceptance as follows:
1- Starting from the introduction and literature review, the literature review is very limited. The authors are requested to provide a better and more broad literature review. The standard is not less than 30 references in journal articles.
2- It is recommended to list the major research gaps and contributions of the paper using a bullet list at the end of the introduction section followed by a paragraph outlining the remainder of the paper.
3- Please make sure that all the abbreviations are carefully defined before the first use of the manuscript.
4- There are plenty of studies concerning the use of the Grey model to predict the settlement of water, what makes this study innovative? Please discuss!
5- The authors used distributed optical fiber sensing to explore the subsidence evolution characteristics of water-conducting fracture zone caused, what are the main advantages and limitations of using this sensing technology over others? What are the other alternatives for this technology? Please discuss!
6- There are several assumptions used to establish the predictive model, How does considering those assumptions affect the results? How can be the model improved and become more realistic by reducing the assumption? Please discuss!
7-The Abstract has not been written carefully. Please improve the writing and the structure of the Abstract. The reviewer is suggesting following the implicit IMRaD abstract style.
8- The conclusion should be more carefully rewritten, summarizing what has been learned and why it is interesting and useful.
9- The discussion section is absent, please provide a discussion section that can discuss the results, limitations, challenges, contributions, and suggestions of the developed method.
Comments on the Quality of English LanguageThe English should be improved based on three main issues:
1- There are mixed tenses along the paper. The author should properly use the present tense and past tense when necessary. Past tense can be used for literature review, whereas the present simple, present progressive, and present perfect can be used elsewhere.
2- There are many problems related to the use of prepositions.
3- Some grammatical mistakes were observed.
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
Comments and Suggestions for AuthorsThe manuscript is very important topic and its original work. It contain new facts, current knowledge and sufficient data. After reviewing the paper here are some suggestions and comments:
1. Title: Make the title more clear and more attractive.
Keywords: Need to add more appropriate keywords
3. Abstract: The abstract cannot be understanding on its owns, it does not contain all the relevant facts. Please re-written it.
4. Introduction: need up to date studies (recent studies)
5. Conclusion: I suggest reorganizing the conclusion.
6. Study limitations and future direction need to be added.
7. Language should be improving with the help of a professional editor.
Comments on the Quality of English Language
The manuscript is need to improving in English language, it should be improving with the help of a professional editor.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThis version was improved a lot compared with the previous version. It is recommended to be published after carefully checking the detail.
Comments on the Quality of English LanguageThe English language should be checked more carefully.
Author Response
Thank you for the work done to improve this article. English has been re-examined and modified.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe paper can be accepted for publication.
Author Response
Thank you for the work done to improve this article.
Reviewer 4 Report
Comments and Suggestions for AuthorsAfter review the revised manuscript. I am recommend to accept the manuscript for publication in present form.
Author Response
Thank you for the work done to improve this article.
