Impacts of Clay Content and Type on Shear Strength and Splash Erosion of Clay–Sand Mixtures

Round 1

Reviewer 1 Report

In this manuscript the authors report the effects of clay content and clay type on splash erosion and shear strength of clay-sand mixtures compared with a clay soil under controlled conditions. Clay-sand mixtures were prepared by mixing varying amounts of the selected clays with pure quartz sand, and then pre-treated with three levels of wetting and drying cycles ,including one without and two wetting and drying cycles. Then, the shear strength in the studied samples was measured by a shear vane. The mixtures and the clay soil were investigated under a rainfall simulator to measure splash erosion rate at three levels of water status, including air-dry, plastic limit, and liquid limit. Previous studies have shown that clay content could regulate various soil mechanical and physical properties as well as soil erodibility. Although previous studies have shown the significance of clay content on soil mechanical properties and splash erosion, few studies have been made to investigate the effects of clay type on these soil variables. The authors are able to demonstrate that the highest values of splash erosion were observed in the samples without the wetting and drying cycle. The splash erosion decreased upon drying and wetting cycles. In addition, the lowest splash erosion was observed at an intermediate water content. Further, the shear strength of the clay-sand mixtures significantly increased upon wetting and drying cycles, showing that splash erosion is not solely controlled by shear strength. And finally, nonlinear power relations were obtained between splash erosion and cohesion, showing that shear strength could explain about 30‒33 % of the splash erosion variability in the studied clay-sand mixtures.

            The authors have done an excellent job in exploring these soil mechanics properties, and it will undoubtedly lead to additional work on the stabilization of soil moisture. I do have one comment to make that should lead to some clarification. The authors use the term “bentonite” as a clay mineral, along with kaolinite and others. However, bentonite forms from the weathering of volcanic ash in seawater, which converts the volcanic glass present in the ash into a clay mineral-rich assembly. Other volcanogenic minerals are also typically included, such as apatite, zircon, plagioclase, biotite and others. So it is not a pure clay mineral itself. The clay mineral in most bentonites is montmorillonite (smectite). But some bentonites also contain illite. So it would be better to use montmorillonite or smectite for that sample. Beyond that, the English grammar and syntax need very careful correction throughout the manuscript prior to its acceptance for publication.

Comments for author File: Comments.pdf

Author Response

Dear Reviewer 

Many thanks for your positive and kind responses. Anyway, based on the other reviewer's comments we improved the manuscript as the new version of the manuscript

Yours sincerely. 

Author Response File: Author Response.pdf

Reviewer 2 Report

Review for the Minerals Journal on the manuscript entitled: “Impacts of clay content and type on shear strength and splash erosion of clay-sand mixtures”.

 (Manuscript ID: minerals-1933449)

 Authors: Shamsollah Ayoubi1, Anashia Milikian, Mohammad Reza Mosaddeghi, and Mojtaba Zeraatpisheh

 Keywords: raindrop; clay minerals; bentonite; zeolite; kaolinite; phlogopite; cohesion.

 The study investigated the effects of clay percentages and type on shear strength and splash erosion of clay-sand mixtures

Here are some of my comments or suggestions in detail:

1.       Title: Please consider capitalizing each word following the journal style.

2.       The abstract should be a total of about 200 words maximum.

3.       Line 11-13: Please consider paraphrasing the sentence.

4.       Line 13: What did you mean by controlled conditions?

5.       Line 20: “without the W&D cycle”, I suggest mentioning it as a control sample.

6.       I suggest improving the introduction part. Addition of more results from the previous study may be useful to the reader (e.x effects of clay content on soil erodibility ..etc).

7.       Line 78: “Soil samples and preparation” If possible, please add the grain size distribution curve of the studied soil/s.

8.       Line 80: “clay soil” how did you know it's clay without soil classification?

9.       Table 1: “clay” “clay soil” what’s the difference? It is confusing.

10. What are the water contents at L.L and PL limits?

11.   Line 101: “Based on precipitation data and the annual rainstorm frequency in Isfahan city” any reference?

12.   Line 102: “rainfall intensity in the splash erosion experiment was premeditated as 60 mm h–1” how the precipitation rate was controlled during the test?

13.   Line 116-118: "The splashed sediments were placed at 110 °C for 24 h to be dried and then weighted to measure soil loss” for the wet soil, how the mass losses were measured? Please explain.

14.   Do you think 2 cycles of wetting-dry are enough? Any justification? Field soils are subject to several natural cycles of wetting and drying. It is supposed that increasing the W-D cycles will lead to a decrease in erosion resistance.

15.   Please check figure 2 c.

16.   Figure 2. What did you mean by symbols like e b j in the top of bars? Please check the whole manuscript carefully to avoid any errors. I suggest proofreading the paper to avoid typos.

17.   Figure 4: Because different soils were studied and each soil has different nature (mineralogy, structure...etc..) so I think it's not reliable to estimate any correlations in this situation. Any justification?

18.   I think referring to Nearing and Bradford [59] and Mouzai and Bouhadef [37] does not support the argument of "the wetting and drying process directed to an increment in .... the cohesion". Could you please clarify this point?

Author Response

Dear Reviewer

As the corresponding author of the manuscript entitled as “Impacts of Clay Content and Type on Shear Strength and Splash Erosion of Clay-Sand Mixtures”, I wish to thank you for your careful evaluation of our manuscript and  your. We did our best to address all the issues raised during the reviewing process. We believe that our research greatly benefited from the suggested changes and further editing. Here we provided our detailed answers to you as highlights specific.

Yours truly

Corresponding author

Review for the Minerals Journal on the manuscript entitled: “Impacts of clay content and type on shear strength and splash erosion of clay-sand mixtures”.

 (Manuscript ID: minerals-1933449)

 Authors: Shamsollah Ayoubi1, Anashia Milikian, Mohammad Reza Mosaddeghi, and Mojtaba Zeraatpisheh

 Keywords: raindrop; clay minerals; bentonite; zeolite; kaolinite; phlogopite; cohesion.

 The study investigated the effects of clay percentages and type on shear strength and splash erosion of clay-sand mixtures

Here are some of my comments or suggestions in detail:

1. Title: Please consider capitalizing each word following the journal style.

Answer: It was done

2. The abstract should be a total of about 200 words maximum.

Answer: It was done

3. Line 11-13: Please consider paraphrasing the sentence.

Answer: It was done

4. Line 13: What did you mean by controlled conditions?

Answer: It was removed.

5. Line 20: “without the W&D cycle”, I suggest mentioning it as a control sample.

Answer: We do believe the current term “without the W&D cycle” representing better than “control sample” and it is common on papers of soil physics

6. I suggest improving the introduction part. Addition of more results from the previous study may be useful to the reader (e.x effects of clay content on soil erodibility ..etc).

Answer: It was done and following discussion was included:

“Moreover, soil distribution size has the significant effects on soil erodibility. In this regard, Huang et al. (2022) indicated that soil K factor showed a negative correlation with the sand content but was positively related to soil silt and clay contents [27].  “

7. Line 78: “Soil samples and preparation” If possible, please add the grain size distribution curve of the studied soil/s.

Answer: Thanks for comment, we just did three size “clay- silt and clay” and showing the grina curve is useless.

8. Line 80: “clay soil” how did you know it's clay without soil classification?

Answer: It was classified as USDA classification based on particle size distribution.

9. Table 1: “clay” “clay soil” what’s the difference? It is confusing.

Answer: “clay soil” was a soil with clay-classification based on USDA which collected from the field.

10. What are the water contents at L.L and PL limits?

Answer: The values are presented in Table 1.

11. Line 101: “Based on precipitation data and the annual rainstorm frequency in Isfahan city” any reference?

Answer: The relevant reference was included.

12. Line 102: “rainfall intensity in the splash erosion experiment was premeditated as 60 mm h–1” how the precipitation rate was controlled during the test?

Answer: It was an automatically apparatus controlled the intensity.

13. Line 116-118: "The splashed sediments were placed at 110 °C for 24 h to be dried and then weighted to measure soil loss” for the wet soil, how the mass losses were measured? Please explain.

Answer: We just needed the dry weight, not losses the water content. Then just we measure the dried soil samples as the soil loss.  

14. Do you think 2 cycles of wetting-dry are enough? Any justification? Field soils are subject to several natural cycles of wetting and drying. It is supposed that increasing the W-D cycles will lead to a decrease in erosion resistance.

Answer: You are exactly right, but because of the limitation of time for doing the research we just considered 2 cycles.  

15. Please check figure 2 c.

Answer: It was corrected.

16. Figure 2. What did you mean by symbols like e b j in the top of bars? Please check the whole manuscript carefully to avoid any errors. I suggest proofreading the paper to avoid typos.

Answer: We was explained in the footnote of the Figure.

17. Figure 4: Because different soils were studied and each soil has different nature (mineralogy, structure...etc..) so I think it's not reliable to estimate any correlations in this situation. Any justification?.

Answer:  It is normal to similar studies for representing these relationships although some uncertainty may be existed.  

18. I think referring to Nearing and Bradford [59] and Mouzai and Bouhadef [37] does not support the argument of "the wetting and drying process directed to an increment in .... the cohesion". Could you please clarify this point?

Answer: It was revised and corrected.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Thank you very much for your response. Please find below my comments and concerns:

Reply to previous comments:

Comment 2: According to the Instructions for Authors (Journal Website): “The abstract should be a single paragraph and should follow the style of structured abstracts, but without headings: 1) Background: Place the question addressed in a broad context and highlight the purpose of the study; 2) Methods: Describe briefly the main methods or treatments applied. Include any relevant preregistration numbers, and species and strains of any animals used. 3) Results: Summarize the article's main findings; and 4) Conclusion: Indicate the main conclusions or interpretations”.

The abstract should be an objective representation of the article: it should contain the objectives, methods, results, and conclusions. Please consider paraphrasing the abstract, not just deleting the sentences.

Comment 6: I think that adding one reference cannot be considered as a sufficient improvement.

Comment 7: “Thanks for comment, we just did three size “clay- silt and clay” and showing the grina curve is useless”.

Line 80-81: . For examining our hypothesis in this study, 15, 30, and 45 kg 100kg-1 of selected clays were mixed with pure sand (quartz with the size range of 0.3–0.8 mm).”

Did you use sand soil or not? Please clarify.

Comment 8: Please consider mentioning the use of the USDA classification in the methodology section.

Comment 13: “We just needed the dry weight, not losses the water content. Then just we measure the dried soil samples as the soil loss”.

The soil was placed in the erosion tray in the wet condition, how did you calculate the soil losses at the dry condition? what happened to the water mass? Please explain how the mass losses were measured?

Comment 16: “Figure 2. Means’ comparisons of the interaction effect of clay type and percentage on cohesion 257 (kPa) of clay-sand mixtures and clay soil (LSD0.05) without wetting and drying (W&D) cycle (a), 258 after one cycle of W&D (b), and after two cycles of W&D (c). Different letters in the same column 259 indicate significant differences (p < 0.05) among land uses”.

You didn't mention anything about symbols like i, k, j, ef, de, fg, h. Please check the whole manuscript carefully to avoid any errors. I suggest proofreading the paper to avoid typos.

New comments:

1.       What did you mean by “soil K factor”, it’s not a common terminology. Is it soil erodibility factor?

2.       Line 78: “The collected clay soil dominantly included montmorillonite, vermiculite, kaolinite, and small portions of chlorite and illite.” How the soil mineralogy was identified?

3.       Line 80: “The soil sample was dried at air temperature and then passed through a 2 mm sieve” we can’t say it’s pure clay soil if it's passed through 2 mm sieve only.

4.       Reference 27 is missing.

5. Please correct the references number“Nearing and Bradford [60] and Mouzai and Bouhadef [38] stated that the wetting and drying process directed to increasing of the aggregation, soil consis"

Author Response

Dear Reviewer

With the best reverences

As the corresponding author of the manuscript entitled as “Impacts of Clay Content and Type on Shear Strength and Splash Erosion of Clay-Sand Mixtures”, I wish to thank you for your careful evaluation of our manuscript and  your. We did our best to address all the issues raised during the reviewing process. We believe that our research greatly benefited from the suggested changes and further editing. Here we provided our detailed answers to you as highlights specific.

Yours truly

Corresponding author

Comment 2: According to the Instructions for Authors (Journal Website): “The abstract should be a single paragraph and should follow the style of structured abstracts, but without headings: 1) Background: Place the question addressed in a broad context and highlight the purpose of the study; 2) Methods: Describe briefly the main methods or treatments applied. Include any relevant preregistration numbers, and species and strains of any animals used. 3) Results: Summarize the article's main findings; and 4) Conclusion: Indicate the main conclusions or interpretations”.

The abstract should be an objective representation of the article: it should contain the objectives, methods, results, and conclusions. Please consider paraphrasing the abstract, not just deleting the sentences. Comment 6: I think that adding one reference cannot be considered as a sufficient improvement.

Answer: It was revised according to your suggestion and more literature review was done.  

Comment 7: “Thanks for comment, we just did three size “clay- silt and clay” and showing the grina curve is useless”.

Answer: Our meant is for showing a standard PSD curve some points are required. We had just three points for clay size (0.002 mm), slit size ( 0.002- 0.002–0.063 mm) and sand size (0.063 – 2 mm) and not sufficient to provide a standard Curve of PSD. Please see the standard PSD curve :

Line 80-81: . For examining our hypothesis in this study, 15, 30, and 45 kg 100kg-1 of selected clays were mixed with pure sand (quartz with the size range of 0.3–0.8 mm).”

Did you use sand soil or not? Please clarify.

Answer: Not sandy soil, just sand. It was mentioned in the previous revised in the text body. Quartz with the size range of 0.3–0.8 mm means pure sand not sandy soil.

Comment 8: Please consider mentioning the use of the USDA classification in the methodology section.

Answer: It was included in the text. Soil Survey Staff (2014)  

Comment 13: “We just needed the dry weight, not losses the water content. Then just we measure the dried soil samples as the soil loss”.

The soil was placed in the erosion tray in the wet condition, how did you calculate the soil losses at the dry condition? what happened to the water mass? Please explain how the mass losses were measured?

Answer: Soils were inserted samples in tray after drying and wetting cycles in the dried condition not wet. Before the test, soil were dried at room temperature and then experimented, so the water content and its changes was not our concern. For evaluating the soil loss, we collected the particles transported to the end of tunnel after experiment and weighted it.

Comment 16: “Figure 2. Means’ comparisons of the interaction effect of clay type and percentage on cohesion 257 (kPa) of clay-sand mixtures and clay soil (LSD0.05) without wetting and drying (W&D) cycle (a), 258 after one cycle of W&D (b), and after two cycles of W&D (c). Different letters in the same column 259 indicate significant differences (p < 0.05) among land uses”.

You didn't mention anything about symbols like i, k, j, ef, de, fg, h. Please check the whole manuscript carefully to avoid any errors. I suggest proofreading the paper to avoid typos.

Answer: In the statistical analysis after analysis of variance (ANOVA) usually  mean comparison is done by various methods such as Tukey, Duncan, LSD, … and the outcome of mean comparison are defined  using the letter on the values or bars for defining there is significant difference between two means or not. If they wuld be similar for two means they are not different statically, otherwise they are different statically. And this approach is very well known in biological, agricultural, ,…sciences. So, those are just the symbols and could not be defined in the text.

New comments:

1. What did you mean by “soil K factor”, it’s not a common terminology. Is it soil erodibility factor?

Answer: it was revised.

2. Line 78: “The collected clay soil dominantly included montmorillonite, vermiculite, kaolinite, and small portions of chlorite and illite.” How the soil mineralogy was identified?

Answer: The methodology was included in the revised manuscript at the Methods section.  

3. Line 80: “The soil sample was dried at air temperature and then passed through a 2 mm sieve” we can’t say it’s pure clay soil if it's passed through 2 mm sieve only.

Answer: We did not claim it is pure clay, is was clay soil according to USDA classification. In this classification based on the clay, silt and sand content soils classified at 12 soil classes and one of them is Clay.

4. Reference 27 is missing.

Answer: It was corrected.

5. Please correct the references number“Nearing and Bradford [60] and Mouzai and Bouhadef [38] stated that the wetting and drying process directed to increasing of the aggregation, soil consis"

Answer: It was corrected. .

Author Response File: Author Response.docx

Round 3

Reviewer 2 Report

Thank you very much for your response.

Here are some of my comments and suggestions:

1)        Lin (186); “based on the Wilding's [34] classification” wrong citation, please fix the error. I recommend proofreading the paper to avoid typos.

2)       “….Huang et al. (2022) indicated……”, “….Wei et al. (2015)……”,”…. Kittrick and Hope’s (1963)…..” In the text, reference numbers should be placed in square brackets [ ]. I recommend proofreading the paper to avoid typos.

3)       “Many scholars stated that soil internal forces induced by…..” Do you think adding a single reference would be evidence that many researchers have confirmed that clay particles and soil organic matter have higher contribution in splash erosion rather than kinetic energy of raindrops? Please add more references.

4)       “Although several studies have shown the significance of clay content on soil mechanical properties and splash erosion [3, 15, 32]”. Reference number 32 is a standard, not a research study. Please recheck it.

 5)       “Kittrick and Hope’s (1963)” reference is missing.

 6)       I suggest adding the XRD graphs showing clay mineral identifications.

7) “Figure 2. Means’ comparisons of the interaction effect of clay type and percentage on cohesion 257 (kPa) of clay-sand mixtures and clay soil (LSD0.05) without wetting and drying (W&D) cycle (a), 258 after one cycle of W&D (b), and after two cycles of W&D (c). Different letters in the same column 259 indicate significant differences (p < 0.05) among land uses”.

You didn't mention anything about symbols like i, k, j, ef, de, fg, h. .

It's confusing. The reader cannot understand what these symbols mean. Please add an appropriate explanation.

Author Response

Dear Editor in Chief of Minerals

With the best reverences

As the corresponding author of the manuscript entitled as “Impacts of Clay Content and Type on Shear Strength and Splash Erosion of Clay-Sand Mixtures”, I wish to thank you for your careful evaluation of our manuscript and your. We did our best to address all the issues raised during the reviewing process. We believe that our research greatly benefited from the suggested changes and further editing.

Yours truly

Corresponding author

Comments of Reviewer

Here are some of my comments and suggestions:

• Lin (186); “based on the Wilding's [34] classification” wrong citation, please fix the error. I recommend proofreading the paper to avoid typos.

Answer: It was corrected

• “….Huang et al. (2022) indicated……”, “….Wei et al. (2015)……”,”…. Kittrick and Hope’s (1963)…..” In the text, reference numbers should be placed in square brackets [ ]. I recommend proofreading the paper to avoid typos.

Answer: It was corrected.

• “Many scholars stated that soil internal forces induced by…..” Do you think adding a single reference would be evidence that many researchers have confirmed that clay particles and soil organic matter have higher contribution in splash erosion rather than kinetic energy of raindrops? Please add more references.

Answer: More references were included

• “Although several studies have shown the significance of clay content on soil mechanical properties and splash erosion [3, 15, 32]”. Reference number 32 is a standard, not a research study. Please recheck it.

Answer: It was revised.

• “Kittrick and Hope’s (1963)” reference is missing.

Answer: It was included.

• I suggest adding the XRD graphs showing clay mineral identifications.

Answer: The XRD diffractogram was included.

• “Figure 2. Means’ comparisons of the interaction effect of clay type and percentage on cohesion 257 (kPa) of clay-sand mixtures and clay soil (LSD0.05) without wetting and drying (W&D) cycle (a), 258 after one cycle of W&D (b), and after two cycles of W&D (c). Different letters in the same column 259 indicate significant differences (p < 0.05) among land uses”.You didn't mention anything about symbols like i, k, j, ef, de, fg, h. .It's confusing. The reader cannot understand what these symbols mean. Please add an appropriate explanation.

Answer:  More explanations were included in the footnote.

Author Response File: Author Response.pdf