Road Performance Evaluation of Unburned Coal Gangue in Cold Regions
Round 1
Reviewer 1 Report
1. What is the main question addressed by the research? This study uses unburned materials, which will waste the calorific value of the materials and is of no value from the perspective of effective resource utilization.
2. Do you consider the topic original or relevant in the field? Does it address a specific gap in the field? It is not enough to show the value of this research only from the perspective of the environment, there is a feeling of using for the sake of using.
3. What does it add to the subject area compared with other published material? No particular contribution is apparent from the current content.
4. What specific improvements should the authors consider regarding the methodology? What further controls should be considered? If it is compared with the materials after combustion, or how serious the environmental pollution is at present, provide quantitative information.
5. Are the conclusions consistent with the evidence and arguments presented and do they address the main question posed? There is no problem in this regard.
6. Are the references appropriate? It's ok.
7. Please include any additional comments on the tables and figures. The place names in Figure 1 should be expressed in English.
Author Response
Response to Reviewer 1’s comments:
- What is the main question addressed by the research? This study uses unburned materials, which will waste the calorific value of the materials and is of no value from the perspective of effective resource utilization.
Response: The authors kindly disagree with the reviewer’s argument. The unburned coal gangue is the byproduct of the coal mining process and consists of 10-20% of the total amount. Traditional treatment involves burning the gangue which can cause serious environmental damages and water pollutions. The goal of this study is to explore the possibility to utilize the unburned coal gangue as a filling material for road embankment in cold regions.
- Do you consider the topic original or relevant in the field? Does it address a specific gap in the field? It is not enough to show the value of this research only from the perspective of the environment there is a feeling of using for the sake of using.
Response: The authors thank for the reviewer’s comment. The idea of using gangue as a filling material for road construction has a long history (Jiang, Ji, and Zuo 2001; Jiang et al. 1999) and the state of the art discussion in regards to the comprehensive utilization of gangue can be found in Li and Wang(2019)’s paper. As for northeastern China, the use of burned coal gangue as a filling material can be traced back to the 1980s. This paper performs a series of laboratory tests to evaluate the performance of unburned coal gangue as a filling material. The study of this paper is directly related to the application of gangue in the field. The goal of this study is to determine if the unburned coal gangue can be used as a filling material in cold regions which will suffer from cyclic freezing-thawing cycles.
Jiang Z, Ji L, Zuo R. (2001). Research on mechanism of crushing-compression of coal waste[J]. Journal of China University of Mining and Technology, 30.
Jiang Z, Zhao D, Sui W, et al. (1999). Study on relationship between consolidation compactness and size grade shortage of coal gangue[J]. Journal of China University of Mining & Technology, 1999(03):12-16.
Li J. and Wang J. (2019). Comprehensive utilization and environmental risks of coal gangue: A review. Journal of Cleaner Production, 239:117946.
- What does it add to the subject area compared with other published material? No particular contribution is apparent from the current content.
Response: The authors thank for the reviewer’s comment. Firstly, most of the published papers study the physical and mechanical properties of burned coal gangue while this study evaluates the physical, chemical, and mechanical performance of unburned coal gangue. Secondly, most of the current studies do not evaluate the performance of the gangue under freezing-thawing effects. However, since Heilongjiang Province located in the seasonal permafrost region and this study evaluates the performance of the unburned coal gangue under cyclic freezing-thawing conditions.
- What specific improvements should the authors consider regarding the methodology? What further controls should be considered? If it is compared with the materials after combustion, or how serious the environmental pollution is at present. provide quantitative information.
Response: The authors thank for the reviewer’s comment. Firstly, the major focus of the study lies in the performance of the unburned coal gangue as a filling material for the application in cold regions. Since water migration is another major factor in determining the long-term performance of the unburned coal gangue, it is recommended to perform the laboratory tests under conditions with and without water supply. As for the second question, it is practically impossible to provide quantitative results of the exact environmental pollution caused by the coal gangue since the carbon and sulfate contents are different from different testing pits.
- Are the conclusions consistent with the evidence and arguments presented and do they address the main question posed? There is no problem in this regard.
Response: The authors thank for the reviewer’s comment. The authors have revised the conclusion section based on the reviewer’s comment.
- Are the references appropriate? It's ok.
Response: The authors thank for the reviewer’s comment. The authors have carefully checked with the references.
- Please include any additional comments on the tables and figures. The place names in Figure 1 should be expressed in English.
Response: The authors thank for the reviewer’s comment. Figure 1 has been revised based on the reviewer’s comment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Consider revising the abstract to better reflect what is in the article. e.g. what research results etc. The article lacks statistics. The authors have not even indicated the uncertainty of the studies performed
Line 8 should state only 1 author for correspondence
Line 10 - 24 should be written in the abstract what was done in the paper
Line 34 a break between 70 and km2 (in other units also)
Line 48 - 50 literature reference to French Ministry of Highway Technology Research
Line 53 gap between 1.91 and g/cm3
Line 118 too high accuracy, consider giving as 1.2% and 4.9%
Line 119 unit at specific gravity
Line 121 Figure 1, give English names of rivers and places
Line 127 gap between 8 and mm and 12 and mm
Line 138 9.74 and 35.18 not too high accuracy?
Line 155 Figure 3 missing uncertainty on graphs, without this it is not possible to assess significance of differences
Line 159 Describe how the chemical components are determined
Line 172 Figure 4 what the dashed lines are, uncertainties are missing
Line 174 - Line 205 describe in more detail the tests if not performed according to the test standard
Line 193 Describe in detail the test method if not described in the standard
Line 194 Why is Specification in quotation marks?
Line 224 Figure 5 lacks uncertainty, correct accuracy, once accuracy 40.28 and once 44, make up your mind
Line 254 how did you achieve different compaction degrees? Did you achieve exactly 94, 96, 98%?
Conclusion 4 this point is correct not only for coal but for aggregate grain size in general
regards to the authors
Author Response
Response to Reviewer 2’s comments:
- Consider revising the abstract to better reflect what is in the article. e.g. what research results etc. The article lacks statistics. The authors have not even indicated the uncertainty of the studies performed.
Response: The authors thank for the reviewer’s comment. The abstract has been revised according to the reviewer’s comment. The major findings of this study have been included in the abstract.
Lines 20-22:“…The typical unburned coal gangue in Heilongjiang region is mainly composed of SiO2, Al2O3, and Fe2O3, which accounts for approximately 91% of the total mass. The unburned coal gangue meets the minimum CBR requirement of 8% after 7 freezing-thawing cycles…”
- Line 8 should state only 1 author for correspondence.
Response: The authors thank for the reviewer’s comment. The authors revised the manuscript so that only 1 author for correspondence.
- Line 10 - 24 should be written in the abstract what was done in the paper.
Response: The authors thank for the reviewer’s comment. To address the reviewer’s concern, the following statement has been added to the abstract to summarize the major laboratory tests that have been performed in this study.
Lines 16-20: “…A series of laboratory tests have been performed to determine the physical and chemical properties of the unburned coal gangue and its performance as a filling material in cold regions. The influence of compaction effort, clay content and numbers of freezing-thawing cycles on the mechanical performance of the unburned coal gangue…”
- Line 34 a break between 70 and km2 (in other units also).
Response: The authors thank for the reviewer’s comment. The corresponding typo has been corrected and the manuscript has been carefully proof checked.
- Line 48 - 50 literature reference to French Ministry of Highway Technology Research.
Response: The authors thank for the reviewer’s comment. The corresponding reference has been added to the reference section.
- Line 53 gap between 1.91 and g/cm3.
Response: The authors thank for the reviewer’s comment. The corresponding typo has been corrected and the manuscript has been carefully proof checked.
- Line 118 too high accuracy, consider giving as 1.2% and 4.9%.
Response: The authors thank for the reviewer’s comment. The authors have corrected the accuracy of the numbers according to the reviewer’s comment.
- Line 119 unit at specific gravity.
Response: The authors thank for the reviewer’s comment. Specific gravity is unitless.
- Line 121 Figure 1 give English names of rivers and places.
Response: The authors thank for the reviewer’s comment. Figure 1 has been revised according to the reviewer’s comment.
- Line 127 gap between 8 and mm and 12 and mm.
Response: The authors thank for the reviewer’s comment. The corresponding typo has been corrected and the manuscript has been carefully proof checked.
- Line 138 9.74 and 35.18 not too high accuracy?
Response: The authors thank for the reviewer’s comment. The authors used a digital balance with an accuracy of 0.0001g. Therefore, the authors think the accuracy is ok.
- Line 155 Figure 3 missing uncertainty on graphs, without this it is not possible to assess significance of differences.
Response: The authors thank for the reviewer’s comment. Figure 3 aims at comparing the mass loss and crush values of the samples obtained from different testing sites. Only one testing sample is used for each testing site and no duplicate testing are performed.
- Line 159 Describe how the chemical components are determined. Line 172 Figure 4 what the dashed lines are, uncertainties are missing.
Response: The authors thank for the reviewer’s comment. The methods of the chemical determination are a standard test. To address the reviewer’s concern, the authors call out the standards for the readers’ convenience.
- Line 174 - Line 205 describe in more detail the tests if not performed according to the test standard. Line 193 Describe in detail the test method if not described in the standard.
Response: The authors thank for the reviewer’s comment. The resilient modulus test is performed according to the test standard.
- Line 194 Why is Specification in quotation marks?
Response: The authors thank for the reviewer’s comment. The specific specification name is added to the manuscript.
- Line 254 how did you achieve different compaction degrees? Did you achieve exactly 94, 96, 98%?
Response: The authors thank for the reviewer’s comment. From the Proctor test, one shall know the maximum dry density of the sample. Based on the maximum dry density, the corresponding dry density of the soil for 94%, 96%, and 98% degree of compactions can be determined. If one knows the volume of the compaction mold, the corresponding amount of mass and water can be determined.
- Conclusion 4 this point is correct not only for coal but for aggregate grain size in general.
Response: The authors thank for the reviewer’s comment. Conclusion 4 has been deleted.
Author Response File: Author Response.pdf
Reviewer 3 Report
Authors should consider briefly mentioning geographical context or any significant features of the sites listed in Figure 1.
The authors use a lot of specialized terms, abbreviations, and acronyms, however, there are many instances where these are not consistently explained or defined upon their first use.
The authors should provide some clarification of the terminology related to compaction effort, e.g. 'blows per layer', a brief explanation about significance of these values would be useful for readers not familiar with these terms.
In the section discussing dynamic resilient modulus, the authors should consider providing a brief introduction or definition of what this modulus signifies. Not all readers are intimately familiar with the parameter to understand its significance.
The authors present the test results effectively. However, they should consider providing more emphasis on the implications of these results, this would contribute to enhancing the overall discussion.
More discussion about how the observed trends relate to the study's objectives and potential practical applications would help to provide a stronger connection between the data and the broader research context.
The authors should consider briefly outlining how the findings could potentially contribute to environmental protection or sustainable development goals in the discussion/conclusion sections.
Author Response
Response to Reviewer 3’s comments:
- Authors should consider briefly mentioning geographical context or any significant features of the sites listed in Figure 1.
Response: The authors thank for the reviewer’s comment. To address the reviewer’s comment, the following description has been added to demonstrate the geographical content of the features in Figure 1.
Lines 121-124: “…Heilongjiang Province has a good reputation for its abundance in coal storage and 90% of the coal was stored at the eastern part of province. In addition, it is estimated that there are approximately 292 unburned coal gangue hills, accounting for a total mass of 576 million tons…”
- The authors use a lot of specialized terms, abbreviations, and acronyms, however, there are many instances where these are not consistently explained or defined upon their first use.
Response: The authors thank for the reviewer’s comment. The authors have proof checked the terminology used in the manuscript and make sure that the necessary explanations are provided for the first time using such terminologies.
- The authors should provide some clarification of the terminology related to compaction effort, e.g. ‘blows per layer’, a brief explanation about significance of these values would be useful for readers not familiar with these terms.
Response: The authors thank for the reviewer’s comment. “blows per layer” means how many lifts per layer during the compaction test. This type of description is specifically used in the Proctor compaction test to describe the testing procedures. To address the reviewer’s concern, additional explanation has been added to the manuscript to help readers better understand the content.
- In the section discussing dynamic resilient modulus, the authors should consider providing a brief introduction or definition of what this modulus signifies. Not all readers are intimately familiar with the parameter to understand its significance.
Response: The authors thank for the reviewer’s comment. To address the reviewer’s concern, additional explanation has been added to the manuscript to help readers better understand the content.
Section 2.1.2: “…The elastic response in unbounded granular materials and subgrades was termed Resilient Modulus to indicate its nonlinearity, and it is the ratio between an applied deviatoric stress to its induced recoverable axial strain…”
- The authors present the test results effectively. However, they should consider providing more emphasis on the implications of these results, this would contribute to enhancing the overall discussion. More discussion about how the observed trends relate to the study's objectives and potential practical applications would help to provide a stronger connection between the data and the broader research context.
Response: The authors thank for the reviewer’s comment. More detailed discussion in regards to the test results has been added to the manuscript to address the authors comments.
- The authors should consider briefly outlining how the findings could potentially contribute to environmental protection or sustainable development goals in the discussion/conclusion sections.
Response: The authors thank for the reviewer’s comment. The following discussion has been added to the conclusion section to address the authors comments.
“The traditional application of unburned gangue has limited consumption and environmental issues. Although unburned coal gangue has good physical and mechanical properties, using unburned coal gangue as roadbed filler not only alleviates the difficulty of land acquisition and soil extraction in mining area road engineering, but also consumes a large amount of accumulated unburned coal gangue, which will not cause environmental pollution problems.”
Round 2
Reviewer 1 Report
All content has been revised according to the suggestions given and is recommended for publication in the journal.
Reviewer 2 Report
Best Regards
