Study on Shear Characteristics of Herbs Plant Root–Soil Composite System in Beiluhe Permafrost Regions under Freeze–Thaw Cycles, Qinghai–Tibet Highway, China

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper study the root-soil composite system shear characteristics under the action of freeze-thaw cycles in the permafrost regions along the Qinghai-Tibet Highway.The direct shear test of root-soil composite system under different times of freeze-thaw (F-T) cycles were conducted and the gray correlation was used to analyze the correlation between times of F-T cycles, water content, root content and the soil shear strength index. The research results can provide theoretical support and practical guidance for further understanding of the mechanisms of shear strength changes in the root-soil composite system under F-T cycles in permafrost regions, as well as for the scientific and effective prevention and control of retrogressive thaw slump in the study area. This is an interesting work. However, this manuscript more like as an test report while not a research article, and the experimental results in the article are too simplified, with relatively poor theoretical significance.

The specific comments are as follows:

(1)the current deficiencies in the research and the objectives of this study  are not exactly corresponding and why is it necessary to standardize unified standard F-T cycles test. The freeze-thaw test method should be developed based on actual working conditions.

(2) The water content of the soil in the area is 30%, and the density is 1.38 g/cm³, with root content of 0.03 g/cm³. Is the soil sample a frozen soil sample? Taking frozen soil samples using the ring knife method is a problem worth considering. How to measure the root content? The water content value should be rounded to one decimal place.

(3)The direct shear test uses 50 kPa, 100 kPa, 200 kPa, and 300 kPa vertical pressures, with a shear rate of 2.4 mm/min. While, according to the “National Standard of China for Geotechnical Test Methods” (GB/T 50123-2019), 2.3.1 section the direct shear test uses 100 kPa, 200 kPa, 300 kPa, and 400 kPa vertical pressures, 2.3.2 section with a shear rate of 0.8 mm/min~1.2 mm/min.

 

(4) Is the root length influence on the shear strength considered in the article?

(5) The author should supplement the direct shear tests results, such as the results of shear stress and shear displacement, and provide a detailed introduction to the method of obtaining the cohesion and internal friction angle of the specimen. The current results have poor reproducibility.

(6)  The reviewer suggest that the calculation results and analysis of grey correlation degree should should be more in-depth,while not only the correlation between soil cohesion and three factors. Especially in the discussion part, the influence of times of F-T cycles, water content, and improved materials s on the F-T shear characteristics of soil under F-T cycles were discussed while not deeply.

Comments on the Quality of English Language

Extensive editing of English language required

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

In line with the proofreading criteria of the publisher, I prepared a reviewer’s report, which would be as follows:

The content of the proposed paper mostly meets the objectives of the journal.

Using the scientific laboratory test methods during the preparation of the case study applied in accordance with the author’s scientific objectives resulted useful scientific achievements.

The references used in the main chapters are relevant and assist the reader to understand the authors proposals. The illustrations used are regular and correct.

In addition to acknowledging the high-quality work, I recommend the following small corrections:

1. In the course of the presentation of the scientific background and methodology of the laboratory experiments in Sections 1 and 2, as well as in the discussion parts of the article in the Section 4, it is recommended to compare the methodology and results of some foreign publications of similar theme in addition to dealing with the case study’s domestic literature.

2. I recommend that the information ("the cohesion of four different water content soils decreases in the following order") in subsection 3.1.2. should be formulated in a more structured way for better understanding the experiment's results.

3. It is also recommended in „Section 5. Conclusions” to specify shortly the possibilities of international theoretical and practical applicability of the present case study research results, as well as the possible directions of future research projects. 

Based on the above, after revision, I suggest the publication of reviewed article.

Comments on the Quality of English Language

Minor editing of English language required

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

1.       In the abstract, the author proposes that “the results of this study provide theoretical support for further understanding of the mechanism of the change of shear strength of the root-soil composite system in the frozen soil region under the action of F-T cycle”. However, this paper only studies the numerical changes of adhesion force, root content and other indicators to establish the correlation relationship, and cannot see the deeper mechanism.

2.       As mentioned in the research background part of the introduction, " Secondly, the existing research on how to enhance the shear strength of the soil after F-T cycles and its benefits to the ecological environment protection is relatively insufficient", and the research on ecological environment protection benefit is also not reflected in this paper. You're telling people that you clearly knew about the deficiency, but your research didn't avoid it either.

3.       The marking colors of A, B, C, etc. in Figure 1 are close to the background color of the picture, making it difficult to identify them, and as can be seen from the experimental operation diagram in Figure 4, the accuracy of weighing 300g of water with a container of about 2L is slightly lower.

4.       The interpretation ability of experimental data is insufficient, especially the interpretation of the results in Figure 6 is not clear enough, and a regular downward trend cannot be seen by comparing the results of 0 cycles and 10 cycles.

5.       In 3.1.2, the author mentions " Through the above analysis, it can be concluded that as times of F-T cycles increases, the greater the water content of the soil, the smaller its cohesion, and among them, the soil with a water content of 15% has the largest cohesion after F-T cycles", which means that the interpretation of key data is inconsistent and not rigorous enough.

6.       In the discussion section, most of the discussion focused on the research results of others, and there was no in-depth discussion on the results of this experiment. In particular, in section 4.3, I do not understand why the root used by the author should be compared with other materials different from the root system. You neither emphasize the characteristics and advantages of the selected root system nor mention the regulatory mechanism of the root system as an improved material.

7.       "The higher the soil water content, the lower its cohesion". This sentence appears many times in the abstract, results and discussion sections, but it is obvious that this doesn't seem right. As can be seen from Figure 7, the cohesion of 15% water content is higher than that of 10% water content.     

Comments on the Quality of English Language

 There are many grammatical errors throughout, such as the first sentence of the introduction. In addition, the author's interpretation of the experimental data is not scientific enough, and the discussion part is not deep enough and lacks logic.

Author Response

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Reviewer 4 Report

Comments and Suggestions for Authors

The paper entitled “Study on Shear Characteristics of Herbs Plant Root-Soil Composite System in Beiluhe Permafrost Regions under Freeze-Thaw Cycles, Qinghai-Tibet Highway, China” designed an experiment to measure the impacts of freeze-thaw cycles, water, and root content on shear strength of soil, and then conducted gray correlation analysis to detect the relationship between these factors. The experiment process is well described, and results are consistent with previous studies. However, I have some concerns that need to addressed during revision.

 

First, the 48 experimental samples for different conditions of water and root content are insufficient. More samples within greater range of root and water content in soil would be helpful to draw conclusions steadily.

 

Second, grey relational analysis was employed in this study, but the authors did not show the reason to choose grey relational analysis instead of other correlation analysis methods such as Pearson correlation, liner regression, and so on. I think authors need to justify their choice here by showing the advantages and applicability of grey relational analysis. In addition, before calculating correlation of two sequences in grey relational analysis, should you normalize the sequences to remove the influence of different units?

 

Third, as figure 6 and 8 shown, internal friction angle of soil samples does not show an obvious change pattern with variation of root and water content. I think further in-depth analysis is necessary here, and so is comparisons with previous studies. Quantitative analysis is more persuasive than describing an unordered trend in figure 6/8.

 

Specific comments:

 

1. Page 1, Introduction section, the first sentence, “is” is missed.

2. Page 3, the last paragraph of Introduction section, the “Objectives of this study” should describe what to do in this study, instead of what had been done.

3. Page 5, “1. (1)” should be replaced by “(1)”

4. Page 6, “2. (2)” should be replaced by “(2)”

5. Page 8, section 3.1.1, the second paragraph, the section of “The increase in cohesion is 0.03 g/cm3 (16.82%) > 0.01 g/cm3 (11.42%) ……after 10 F-T cycles, the increase in cohesion of soil samples with different root contents is 0.03 g/cm3(41.10%) > 0.05 g/cm3(11.35%) > 0.01 g/cm3(9.51%).” consists of too many numbers, and could be shown clearly in a table or a figure. Similar suggest for corresponding paragraph in section 3.1.2.

6. Page 8, equation (2), the subscript of Sigma should be “k=1”, not “i=1”.

7. In section 3.1.1, Figure 5 shown that the most significant increase in soil cohesion with a root content of 0.03 g/cm3, could authors conduct further analysis/discussion why 0.03 is the best root content value to increase shear strength of soil?

8. P10, section 3.1.2, “it can be concluded that as times of FT cycles increases, the greater the water content of the soil, the smaller its cohesion,” is not rigorous, for it can be seen from Figure 7 that under the same FT cycles, the cohesion of soil with 10% water content is lower than that of 15% water.

9. I found some English writing errors, such as the first sentence of first paragraph in section 3.1.1 on Page 8, “As shown in Figure 5, the change trend of soil cohesion under F-T cycles for soil samples with the same water content and density but different root content in the study area.”. There are other similar grammar errors on Page 9 and 10. Please check throughout full text to clear English writing errors.

 

Comments on the Quality of English Language

English writing needs to be improved.

Author Response

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Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The author has carefully revised the manuscript based on the review comments, and now it can be accepted.

Comments on the Quality of English Language

The author has carefully revised the manuscript based on the review comments, and now it can be accepted.

Author Response

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Reviewer 3 Report

Comments and Suggestions for Authors

In-depth discussion is extremely required.

Comments on the Quality of English Language

Chinglish needs serious revision. For example "....think that, .......think that......"

Author Response

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Reviewer 4 Report

Comments and Suggestions for Authors

Since there are many methods to normalize data, I suggest the author to introduce the method of normalization in this study briefly (a formula is preferred) in section 2.5, or section 3.2, or title of table 6.

In my point of view, the manuscript is significantly improved by addressing reviewers’ concerns.

Author Response

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