The Trend of Permeability of Loess in Yili, China, under Freeze–Thaw Cycles and Its Microscopic Mechanism

Round 1

Reviewer 1 Report

It is still no clear connection between studies done and landslides.

Author Response

Please see the attachment.

Author Response File: Author Response.doc

Reviewer 2 Report

General comments:

This is a resubmission of article "water-1282290-peer-review-v1". The paper has changed only very marginally and most if not all of my original comments still stand.

Unfortunately I do not have time at the moment to go through the article in detail again but the indicated changes do not seem to tally with actual changes between the two revisions. Based on these responses I would still encourage rejection. Although the responses seem sound, a large number of the comments have been misunderstood or the corrections do not add the required amount of detail (e.g. the replaced Figure 1 is still incomplete and had not actually changed from the original submission). Best wishes

Author Response

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Author Response File: Author Response.doc

Reviewer 3 Report

Analyses (microscopic) on cyclic freeze-thaw in loess are currently a very fashionable research topic. This manuscript is the best proof of that.  I have read the text and basically can only write a laurel.Good structure, good basic research, great presentation of data (tables, graphics) and adequate participation in the discussion.  I accept the whole thing.

Author Response

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Author Response File: Author Response.doc

Reviewer 4 Report

Dear Authors,

I have read your manuscript with great interest as the subject of your work is something interesting and relevant to natural hazards. In addition, as you stated your research questions have not been properly address yet, and it is an important issue to tackle in arctic or cold regions. The manuscript is well written and only minor spelling check is needed. The manuscript also well structured and easy to follow. The scope of the manuscripts fits well to the aim of the journal, Water.

While the manuscript is valuable and it would be a good reading for the audience of Water, there are some issues that the Authors need to answer. I have provided an annotated PDF file with my comments, and it should be easy for the Authors to go through of them one by one. Here just few key comments.

1) the manuscript operates a large number of particle geometry parameters that need to be defined and introduced to the reader that they understand those terms (aspect, radius, etc) in a same way the Authors used.

2) in many of the key figures, the figure captions are not enough and extra information need to be provided that the reader can understand the figures.

3) in many figures the actual variation looks to me more complex that it has been explained. Sometimes the initial values essentially the same than the values obtained over 60 cycles. This has to be explained, especially that there are some fluctuating pattern in the first 10 cycles.

4) there are diagrams where the variations are really small. For instance the fractal dimensions has very low variations, and hard to see trends on the results especially without some sort of statistical approach to say that there is.

5) the discussion provides very little global comparison. There must be similar studies elsewhere, and even some basic comparison would elevate the value of this work.

Overall I think a moderate revision is needed prior acceptance can be considered.

Kind regards,

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.doc

Round 2

Reviewer 4 Report

It seems the revised manuscript is ready for acceptance as the Authors followed the reviewer recommendations in sufficient way.

Author Response

Thank you for your comment.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Review is limited, number of works mentioned could be improved.

Number of samples could be more for the conclusion the authors have made.

Conditions of freezing/thawing in situ are not clear.

Most important, if the natural loess is considered as to be still capable to be changed under the freezing/thawing stress, why in nature ( being affected unlimited times there) it did not come to the “equilibrium”, which authors have seen at experiment? It has to be explained 

Reviewer 2 Report

General comments:

The paper presents an exploration of the effects of freeze-thaw cycling on the microstructure of loess and remolded loess, assessed via permeability and porosity.

The experimental programme is poorly described and contains significant flaws. The authors do not state any recognised testing methods. Methods that are stated are presented only briefly, meaning that the results are difficult (if not impossible) to interpret.

The written style is quite repetitive in places and the paragraphination should be improved. It is not usual to refer to "we" throughout the document but this is left to the stylist's discretion.

Detailed comments:

Ln 24. A transition to an ordered state from a disordered state is not consistent with thermodynamics

Ln 28. "the overall porosity of remolded loess porosity" does not make sense

Ln 46-47. Permeability coefficients (k) can vary by many orders of magnitude. Why do the authors state here only 1 or 2? From the context, it is not clear if the authors are referring to permeability coefficients for a given soil, under loose or compacted conditions.

Ln 49. New paragraph at "Recent"

Ln 61. The citation for reference [21] seems misplaced

Ln 77-80. This is an unusual way to report optimum water contents and maximum dry densities. The authors should state the method used and then provide the values.

Figure 1. The particle grading curves are incomplete and should be presented in full

Subsection 2.2. Freeze-thaw testing should be carried out according to a testing method that is chosen to suit the in situ conditions. It is unlikely that the real conditions were a constant -20 degrees C for 15h and then +15 degrees C fr 9 hours. The authors should state a testing method and, if it was modified, the reasons why. Meteorological data could be presented in a figure to support this. What was the specimen water content prior to freeze-thaw testing? This is critical information to understand the effects of thermal cycling.

Ln 91. Again, the authors should state the testing method

Ln 96. It is unusual to include a conversion factor when the natural logarithm could be used. The authors should provide a source for this modified expression

Ln 100-101. Are these the same samples as used for permeability testing? The authors must describe their testing programme in more detail, including the number of tests and replicates.

Ln 107-108. Binarisation is a highly subjective process and must be discussed in more detail

Ln 112. Do the authors mean "water content" here, instead of "porosity"?

Figure 2. The caption is poor and should be more descriptive. Units are missing for water content and signal amplitude

Ln 126. The statement that relaxation times are proportional to the pore sizes requires a reference or further explanation

Ln 140. I have not seen the use of capital lambda to refer to trends before. From the context, are the authors using capital lambda to refer to a peak (i.e. here, " three Λ-trends" means "three-peaked trends". If so, perhaps replacing the symbol capital lambda with "peak" would improve the readability

Ln 144. The authors have not discussed how the loess was remolded, or when (i.e. after freeze-thaw cycles). This must be presented and discussed.

Ln 161. How do the authors know that the SEM images were representative of the whole sample? Choosing an inappropriate image will greatly affect (detrimentally) the following results

Ln 161. The processes used within Image Pro Plus to binarise the images must be discussed. What is the image resolution? What were the threshold values?

Table 1. It would be useful to present a binarised image where these particles have been identified, rather than only presenting results in a table

Table 1. How was the fractal dimension determined? Fractal dimensions close to 1 suggest that these are the fractal dimensions of particle outlines but this is not stated, nor is how outlines were determined

Ln 183-184. That Figure 7 does not show results for the black or green classes, these results should sum to 100%?

Ln 184-187. The authors have not provided a statistical analysis of these (or other) changes. Given the only general trend in the data, it is not clear whether this trend is significant.

Figure 7. That groups <2um and 2-5um do not appear suggests that this was either below the scanning resolution or that these classes were inappropriate. Why were these classes selected? All particles <5um may have appeared in the 5-20um category, depending on the resolution chosen.

Ln 196. The authors use "abundance" to describe particle shape but this does not seem to be the appropriate terminology. Given that the value is a comparison of the major and minor axis lengths (in 2D), a more appropriate term might be "eccentricity" or "ellipticity"

Ln 214-218. The authors suggest that fractal dimension D reduced with the number of freeze-thaw cycles but, again, no statistical analysis is presented. The variation shown in Figure 9 is minor.

Ln 230-233. It is noted that a separate discussion section is provided, however, again, the variation presented in Figure 10 requires considerably more explanation, for example how the directional probability entropy was determined. Note that the axis labels in Figure 10 are incorrect.

Table 2. It is not good practice to present data in the form of a table and a figure. Unless the extra data in the table is required, figure 11 is seemingly the only information that is needed

Ln 248-250. Only one peak is evident in Figure 12 for the undisturbed loess (but perhaps three distinct gradient changes)

Ln 269. TE must be defined

Eqn 3. The equation is in terms of T_2free but the authors state that surface relaxation mechanisms dominate. Should Eqn 3 be in terms of T_2surface?

Ln 277. What is the relevance of mercury to this test?

Table 3. Units are missing. What is the "angle" property?

Ln 313-314. The order of the stated variables is different to the order in which they are presented in Tables 3 and 4.

 

Reviewer 3 Report

For authors and editors

The paper is very weak and should be rejected.

Those are the following reasons

1. The conclusions are far too long…
2. The discussions do not exist, is minimal. The conclusions should be 1/10 of the discussion
3. The methods are old and there are no statistical methods properly applied
4. The methods section shows results
5. The results section is very descriptive. We need more statistics
6. The introduction is not informative enough
7. There are a long list of references to be readed by the authors

The figures are poor, and can be substituted 

Comments for author File: Comments.pdf