Experimental Study on the Mechanical Properties of Saturated Tailing Sand with Different Particle Sizes

Round 1

Reviewer 1 Report

Point 1: The abstract is too short that it lacks the essential contents, including context/purpose (1-2 sentences), methods (1-2 sentences), results (3-4 sentences), interpretations (3-4 sentences), and conclusion (1-2 sentences).

Point 2: The introduction does not provide a good research background/solid rationale/argument of why the current study is crucial. It does not explicitly emphasize the research gap from the previous works stated.

Point 3: The materials and methods section is also poorly written. The reviewer thinks that the moisture content of tailings should be generally higher near the release point. Kindly clarify this idea. For Figures 2 and 3, kindly replace the y-axis to % passing finer and reverse the values in the x-axis. Consider marking d₁₀, d₃₀, d₅₀, and d₆₀ also. Kindly make sure to use appropriate nomenclatures/symbols. At what depth were the samples collected? Kindly explicitly state if the samples collected were disturbed or undisturbed samples. Likewise, kindly explicitly specify or use the terms remolded and (or) reconstituted specimens. Also, kindly explicitly mention that the study employed a triaxial test scheme. Why UU test? Kindly classify the samples according to USCS or AASHTO, whichever is more appropriate based on the application field. What was the basis for the values presented in Tables 2 and (or) 3?

Point 4: In Table 1, kindly define the variables used. Generally, kindly define all symbols entirely and (or) acronyms/abbreviations during their first appearance and use them consistently throughout the paper.

Point 5: Kindly consider a more appropriate term for the particle size range (i.e., with a narrow range) rather than single-particle size.

Point 6: What is the definition of stress at failure for the triaxial UU test results? Is it peak stress or residual stress? Or is it at some axial strain when the stress-strain curve does not explicitly show a peak or residual stress?

Point 7: The reviewer is confused about the permeability test performed by the authors. The reviewer suggests explicitly explaining the details of the test.

Point 8: When the specimens subjected to a UU triaxial test are saturated (i.e., S = 100%), the Mohr-Coulomb failure envelope is generally horizontal, which means that the Mohr’s circle, regardless of the applied confining pressure, does not grow, but will only translate. Hence, the reviewer is skeptical about the results presented in the current study.

Point 9: The reviewer also has reservations about the reported hydraulic conductivity values, as the test program needs to be discussed in detail.

Point 10: The results section is written poorly. Likewise, there are no discussions provided nor comparison or benchmarking of results from previous works. The reviewer suggests avoiding listing or enumerating the observations using numerals. Write in paragraph form.

Point 11: Cite more relevant papers. Follow the correct format when citing references also. Likewise, follow the correct format when listing references. Make sure to complete all sections after the conclusion part.

Point 12: Follow the correct style or format when listing authors and their affiliations.

Author Response

Point 1: The abstract is too short that it lacks the essential contents, including context/purpose (1-2 sentences), methods (1-2 sentences), results (3-4 sentences), interpretations (3-4 sentences), and conclusion (1-2 sentences).

Response: Thanks for your question. The abstract part of the article has been revised and the relevant content has been added.

 

Point 2: The introduction does not provide a good research background/solid rationale/argument of why the current study is crucial. It does not explicitly emphasize the research gap from the previous works stated.

Response:Thank this reviewer for reminding this point. At the beginning and end of the introduction section of the revised article, the importance of the study and the difference from previous studies are emphasized.

 

Point 3: The materials and methods section is also poorly written. The reviewer thinks that the moisture content of tailings should be generally higher near the release point. Kindly clarify this idea. For Figures 2 and 3, kindly replace the y-axis to % passing finer and reverse the values in the x-axis. Consider marking d10, d30, d50, and d60 also. Kindly make sure to use appropriate nomenclatures/symbols. At what depth were the samples collected? Kindly explicitly state if the samples collected were disturbed or undisturbed samples. Likewise, kindly explicitly specify or use the terms remolded and (or) reconstituted specimens. Also, kindly explicitly mention that the study employed a triaxial test scheme. Why UU test? Kindly classify the samples according to USCS or AASHTO, whichever is more appropriate based on the application field. What was the basis for the values presented in Tables 2 and (or) 3?

Response:Thanks for your question. Because water in Chengchao Iron Mine will converge in the place far away from the ore drawing mouth along with seepage, the water content will be higher the farther away from the ore drawing mouth. The gradation experiment is only to prove the poor gradation of the test materials, so the author believes that it is not necessary to replace the ordinate coordinate more carefully, and the abscissa represents the particle size of sand by logarithmic coordinate, which is also the method adopted in most papers. The inverse transfer of the ordinate result in an unintuitive image. The various gradation parameters have been listed in Table 2 for easy access to the data. Samples were collected at a depth of 40cm and the samples collected were undisturbed, and these questions have been supplemented in the test material section in the modified article. The shear strength index of triaxial test should conform to the actual state as far as possible. The unconsolidated and undrained test is suitable for saturated tailing sand with small permeability coefficient, and the total stress shear strength index can be measured by the unconsolidated and undrained test.

The data particle size in Table 2 is the particle size range obtained after the screening of the taken tailings, and the water content and dry density are calculated, as supplemented by the authors in the test protocol of Section 3.

The Cc and Cu in Table 3 are adjusted for the grading according to the particle size of the sample taken by controlling one of the variables to change the other.

 

 

 

 

Point 4: In Table 1, kindly define the variables used. Generally, kindly define all symbols entirely and (or) acronyms/abbreviations during their first appearance and use them consistently throughout the paper.

Response:Thank this reviewer for reminding this point. These symbols have already been defined in the modified text.

 

Point 5: Kindly consider a more appropriate term for the particle size range (i.e., with a narrow range) rather than single-particle size.

Response:Thank this reviewer for reminding this point. A single particle size refers to a certain particle size interval. In this paper, unconsolidated and undrained shear tests were carried out for tailings sand in the interval of less than 0.075mm, 0.075-0.1mm, 0.1-0.25mm, 0.25-0.5mm and 0.5-1mm, respectively. In order to avoid the reader's misunderstanding, the author has made corrections in the article.

 

Point 6: What is the definition of stress at failure for the triaxial UU test results? Is it peak stress or residual stress? Or is it at some axial strain when the stress-strain curve does not explicitly show a peak or residual stress?

Response:Thank this reviewer for reminding this point. Due to the triaxial test under the condition of single particle size, for the sample with relatively uniform particle size, the stress-strain curve belongs to an elastic-plastic curve, which does not obviously show the peak stress or residual stress.

 

Point 7: The reviewer is confused about the permeability test performed by the authors. The reviewer suggests explicitly explaining the details of the test.

Response:Thank this reviewer for reminding this point. The test method for the percolation section has been supplemented to the article.

 

Point 8: When the specimens subjected to a UU triaxial test are saturated (i.e., S = 100%), the Mohr-Coulomb failure envelope is generally horizontal, which means that the Mohr’s circle, regardless of the applied confining pressure, does not grow, but will only translate. Hence, the reviewer is skeptical about the results presented in the current study.

Response:Thank this reviewer for reminding this point. The phenomenon you mentioned does exist in cohesive soil. Foundation soil is composed of gas phase, liquid phase and solid phase. In a strict sense, saturated soil means that the voids in the soil are filled with water. However, the geotechnical test shows that the saturation of the soil is generally difficult to reach 100%, but the B value is above 0.95, and we also think that the soil is saturated. So the internal friction angle you see is not 0.

 

Point 9: The reviewer also has reservations about the reported hydraulic conductivity values, as the test program needs to be discussed in detail.

Response:Thank this reviewer for reminding this point. The authors supplemented the methodology of the trial in the infiltration assay.

 

Point 10: The results section is written poorly. Likewise, there are no discussions provided nor comparison or benchmarking of results from previous works. The reviewer suggests avoiding listing or enumerating the observations using numerals. Write in paragraph form.

Response:Thank this reviewer for reminding this point. The authors have revised these results in the original text.

 

Point 11: Cite more relevant papers. Follow the correct format when citing references also. Likewise, follow the correct format when listing references. Make sure to complete all sections after the conclusion part.

Response:Thank this reviewer for reminding this point. The authors have increased the number of references cited and have also modified the format of other documents. The authors supplemented the missing parts as requested.

 

Point 12: Follow the correct style or format when listing authors and their affiliations.

Response:Thank this reviewer for reminding this point. At the beginning of the article, I have made changes to the format.

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper presents the results of experimental studies on the mechanical properties of tailing sand. The authors conducted a study for a sand of varying granularity from the Chengchao iron ore mine in Ezhou, Hubei province. Similar studies can be found in the literature. However, I have not found a study of sand collected from a tailing pond in an iron ore mine. In addition, the collected material was quite well characterized by taking SEM photos. In my opinion, the work contains elements of scientific novelty. However, the authors should better demonstrate in the introduction the elements of scientific novelty contained in the work. The sentence presented in the introduction is insufficient: "The research on the mechanical properties of tailings sand has been carried out in-depth, but there are still many urgent questions about the relationship between particle size and strength, so further exploration is needed." In addition, the description of the experiment and the research results were incorrectly presented. For this reason, I propose to direct the paper for major revision. Detailed comments below.

1. Page 2: „Figure 1. Field sampling.” In my opinion, the presented photo does not allow to assess the place of sampling. I propose to post a plan of the tailing pond.

2. I did not find explanations for many designations in the text (e.g. m0, md, cu, cc, and other). Of course, I can guess their meaning. However, there should be no place for conjecture in scientific work.

3. I did not find information on the statistical analysis of the results in the text. How many independently taken samples have the tests been carried out?

4. The authors should apply the structure of the scientific work, for example: Introduction, Materials and methods (description of the equipment used in the research, measurement methodology, measurement accuracy, statistics, etc.), Results and discussion, Conclusion. I proposes to arrange the work anew and add the missing element. In particular, the description of the apparatus and statistics.

5. Page 7: “The peak partial stress of the specimens increased with the increase of particle diameter under the same density and under the same circumferential pressure conditions.” I cannot find the described changes in fig. 8. Peak?

6. Page 9 “curvature factor”, Page 5, 6 and other “coefficient of curvature”, page 17 “curvature coefficient”. I propose to standardize the nomenclature throughout the work.

7. For example: page 9 (5) “When the confining pressure is 100kPa, the original graded sand sample is weakly softening type damage; when Cc =1 and Cc =2, the sand sample is weakly hardening type damage; when Cc =1.5 and Cc =3, the sand sample is weakly softening type damage; when Cc =2.5, the sand sample is strongly softening type damage.” What does "weakly hardening" or "strongly softening" mean?

8. What does the "molar circle" mean?

9. The introduction states: “Based on the above research status and problems, this paper aims to study the effect of particle size on the physical and mechanical properties and steady-state characteristics of tailings by changing the particle size to derive the sand sample size or grading requirements for optimal strength.” What does "optimal strength" mean? I did not find information about the optimal strength value in the conclusion.

Author Response

The paper presents the results of experimental studies on the mechanical properties of tailing sand. The authors conducted a study for a sand of varying granularity from the Chengchao iron ore mine in Ezhou, Hubei province. Similar studies can be found in the literature. However, I have not found a study of sand collected from a tailing pond in an iron ore mine. In addition, the collected material was quite well characterized by taking SEM photos. In my opinion, the work contains elements of scientific novelty. However, the authors should better demonstrate in the introduction the elements of scientific novelty contained in the work. The sentence presented in the introduction is insufficient: "The research on the mechanical properties of tailings sand has been carried out in-depth, but there are still many urgent questions about the relationship between particle size and strength, so further exploration is needed." In addition, the description of the experiment and the research results were incorrectly presented. For this reason, I propose to direct the paper for major revision. Detailed comments below.

 

1. Page 2: „Figure 1. Field sampling.” In my opinion, the presented photo does not allow to assess the place of sampling. I propose to post a plan of the tailing pond.

Response: Thank this reviewer for reminding this point. I have added the photo of the sampling sites in Figure 1.

 

2. I did not find explanations for many designations in the text (e.g. m0, md, cu, cc, and other). Of course, I can guess their meaning. However, there should be no place for conjecture in scientific work.

Response: Thank this reviewer for reminding this point. I have made corrections to the problem you mentioned.

 

3.I did not find information on the statistical analysis of the results in the text. How many independently taken samples have the tests been carried out?

Response: Thank this reviewer for reminding this point. Samples were collected from 9 sampling points, and 3 groups of samples were taken from each sampling point, a total of 27 independently collected samples.

 

4. The authors should apply the structure of the scientific work, for example: Introduction, Materials and methods (description of the equipment used in the research, measurement methodology, measurement accuracy, statistics, etc.), Results and discussion, Conclusion. I proposes to arrange the work anew and add the missing element. In particular, the description of the apparatus and statistics.

Response:Thank this reviewer for reminding this point. The author supplemented the relevant content according to the requirements, and revised and adjusted the original text.

 

5. Page 7: “The peak partial stress of the specimens increased with the increase of particle diameter under the same density and under the same circumferential pressure conditions.” I cannot find the described changes in fig. 8. Peak?

Response:Thank this reviewer for reminding this point. The statement here should be that the peak partial stress of the sample increased with the particle size at 50kPa and 100kPa circumference pressures.

 

6.Page 9 “curvature factor”, Page 5, 6 and other “coefficient of curvature”, page 17 “curvature coefficient”. I propose to standardize the nomenclature throughout the work.

Response:Thank this reviewer for reminding this point. This place is an error of the author in the translation, which should be the coefficient of curvature.

 

7.For example: page 9 (5) “When the confining pressure is 100kPa, the original graded sand sample is weakly softening type damage; when Cc =1 and Cc =2, the sand sample is weakly hardening type damage; when Cc =1.5 and Cc =3, the sand sample is weakly softening type damage; when Cc =2.5, the sand sample is strongly softening type damage.” What does "weakly hardening" or "strongly softening" mean?

Response:Thank this reviewer for reminding this point. To facilitate the reader's understanding, the author adds the theoretical basis of the shear strength in the revision of section 3, which introduces the source of the relevant words.

 

8.What does the "molar circle" mean?

Response:Thank this reviewer for reminding this point. This has a problem in translation and should be Mohr circle. This problem was corrected in the text.

 

9. The introduction states: “Based on the above research status and problems, this paper aims to study the effect of particle size on the physical and mechanical properties and steady-state characteristics of tailings by changing the particle size to derive the sand sample size or grading requirements for optimal strength.” What does "optimal strength" mean? I did not find information about the optimal strength value in the conclusion.

Response:Thank this reviewer for reminding this point. The expression is not appropriate here, and the purpose of the test is to obtain the grading of the sand sample with the best shear strength and the best seepage effect. In the modified conclusion part, the author explains the particle grading with the best shear strength under different peripheral pressures. The seepage test of these gradations has also obtained the particle grading with the best seepage effect.

Author Response File: Author Response.pdf

Reviewer 3 Report

The authors examined shear properties of tailing sand with different grading which is artificially made. Those experimental results were shown in the manuscript. However, the reviewer doubt whether testing method adopted in the study is proper or not. Moreover, it is difficult to analyse the mechanism of variation of shear strength from those kinds of tests. Anyway, following items are comments to revise the manuscript.

 

1. Title: Is "saturated" correct? If so, please show the Skempton's B value is greater than 0.95.

 

2. Page 1, line 6 from the bottom: The sentence of "that with the increase of dry density, the denseness of the specimen increases, and the work to be done by the external force to overcome the friction between the aggregates will increase when damage occurs, making the cohesive force and internal friction angle show an increasing trend" is very tedious and difficult to follow this meaning. Please rephrase it with plain English.

 

3. Title of Figure 5: What is the difference between powder particle in the title and chalk grains in the text. Consistent words should be used.

 

4. Page 5: Please check the sentence of "more uniform distribution, adhesion There are few phenomena, and more pores on the surface of the particles"

 

5. Tables 2 and 3: Moisture content was 12% in the tables. However, the authors have explained "this paper selects the effect of particle size on tailings strength under the condition of 15% moisture content". Which is correct value?

 

6. Page 6, "The extracted natural sand was cleaned": What kind of clean was conducted? Were plate-like structures washed away during cleaning? 

 

7. Please describe the specimen preparation method to achieve a certain dry density. Furthermore, please provide the values of degree of saturation.

 

8. Unconsolidated undrained shear test: Why was "unconsolidated undrained test" chosen? Was excess pore water pressure generated with depth in the field? The reviewer considered this is unsaturated soil because phi is not zero from the Fig.9. Volume change occurs when applied stresses increases because of unsaturated soil. Therefore, unconsolidated is not proper word.

 

9. Table 4: The values c' and phi' are shown in the table. The reviewer thinks that the authors calculated those values from effective stress paths during shearing. Please show the results of pore water pressure during shearing.

 

10. Conclusion (1): The reviewer cannot understand the sentence of "The more coarse grains there are, the less cohesive force is generated when shear damage occurs, and the larger the internal friction angle is.". Please explain more clearly. Which figures are indicating this result in the manuscript?

 

11. Conclusion (3), "The shear strength of specimens with <0.075 mm is greater when shear occurs in single grain size specimens.": This fact is opposite result to that shown in Fig. 8. Additional explanation is needed for this.

 

Author Response

The authors examined shear properties of tailing sand with different grading which is artificially made. Those experimental results were shown in the manuscript. However, the reviewer doubt whether testing method adopted in the study is proper or not. Moreover, it is difficult to analyse the mechanism of variation of shear strength from those kinds of tests. Anyway, following items are comments to revise the manuscript.

 

1. Title: Is "saturated" correct? If so, please show the Skempton's B value is greater than 0.95.

Response:Thank this reviewer for reminding this point. The tests were all saturated tailings used, and the authors have supplemented the B value greater than 0.95 in the test protocol section.

 

2. Page 1, line 6 from the bottom: The sentence of "that with the increase of dry density, the denseness of the specimen increases, and the work to be done by the external force to overcome the friction between the aggregates will increase when damage occurs, making the cohesive force and internal friction angle show an increasing trend" is very tedious and difficult to follow this meaning. Please rephrase it with plain English.

Response:Thank this reviewer for reminding this point. The authors have revised the original text.

 

3. Title of Figure 5: What is the difference between powder particle in the title and chalk grains in the text. Consistent words should be used.

Response:Thank this reviewer for reminding this point. There is no difference between the two, this is a mistake in translation, and the author has corrected it in the text.

 

4. Page 5: Please check the sentence of "more uniform distribution, adhesion There are few phenomena, and more pores on the surface of the particles"

Response:Thank this reviewer for reminding this point. Something went wrong with the translation of this sentence in the article and has been revised by the author.

 

5. Tables 2 and 3: Moisture content was 12% in the tables. However, the authors have explained "this paper selects the effect of particle size on tailings strength under the condition of 15% moisture content". Which is correct value?

Response:Thank this reviewer for reminding this point. The author has made a statement on this issue in the paper. Due to the limitation of sampling depth, the measured water content is relatively small compared with the actual value, so the influence of particle size on tailings strength under the condition of 15% water content is selected in this paper.

 

6. Page 6, "The extracted natural sand was cleaned": What kind of clean was conducted? Were plate-like structures washed away during cleaning?

Response:Thank this reviewer for reminding this point. Here is a clerical error, the tailings tailings sand do not need to be cleaned, the author has revised the original text.

 

7. Please describe the specimen preparation method to achieve a certain dry density. Furthermore, please provide the values of degree of saturation.

Response:Thank this reviewer for reminding this point. The dry density calculation method as well as the saturation is explained in the experimental protocol section of Section 3.

8. Unconsolidated undrained shear test: Why was "unconsolidated undrained test" chosen? Was excess pore water pressure generated with depth in the field? The reviewer considered this is unsaturated soil because phi is not zero from the Fig.9. Volume change occurs when applied stresses increases because of unsaturated soil. Therefore, unconsolidated is not proper word.

Response:Thank this reviewer for reminding this point. The shear strength index of the three-axis test should meet the actual state as far as possible, and the non-consolidation and undrainage test is suitable for saturated tailings with small permeability coefficient. The foundation soil is composed of gas phase, liquid phase and solid phase. In a strict sense, the saturated soil is filled with the gaps in the soil and filled with water. However, the geotechnical test shows that the saturation of the soil is generally difficult to reach 100%, but the B value is above 0.95, and we also think that the soil is saturated. So the internal friction angle you see is not 0.

 

9. Table 4: The values c' and phi' are shown in the table. The reviewer thinks that the authors calculated those values from effective stress paths during shearing. Please show the results of pore water pressure during shearing.

Response:Thank this reviewer for reminding this point. The table mainly records the tailings strength under different test conditions to obtain the influence of the surround pressure on the consolidation and non-drainage shear test, so the authors did not record the pore water pressure.

 

10. Conclusion (1): The reviewer cannot understand the sentence of "The more coarse grains there are, the less cohesive force is generated when shear damage occurs, and the larger the internal friction angle is.". Please explain more clearly. Which figures are indicating this result in the manuscript?

Response:Thank this reviewer for reminding this point. The authors have modified the conclusion, and this result is shown in the third part of the paper: Effect of particle size on unconsolidated undrained shear tests.

 

11. Conclusion (3), "The shear strength of specimens with <0.075 mm is greater when shear occurs in single grain size specimens.": This fact is opposite result to that shown in Fig. 8. Additional explanation is needed for this.

Response:Thank this reviewer for reminding this point.There was a problem in the translation of this sentence and the author has changed the conclusion.

Author Response File: Author Response.pdf

Reviewer 4 Report

Results and discussion should be revised effectively.

Applications of the results are missing

Existing kinds of literature are missing. 

Author Response

1.Results and discussion should be revised effectively.

Response:Thank this reviewer for reminding this point. The authors have revised it.

 

2.Applications of the results are missing

Response:Thank this reviewer for reminding this point. The authors supplement the relevant statement of the article.

 

3.Existing kinds of literature are missing. 

Response:Thank this reviewer for reminding this point. The authors have revised the reference section.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Please find the attached package. The package contains the reviewer's comments on the author's responses and the commented revised manuscript.

The reviewer strongly recommends availing of English editing services or carefully proofreading the paper.

Comments for author File: Comments.zip

Author Response

Please find the attached package. The package contains the reviewer's comments on the author's responses and the commented revised manuscript.

Point 1: The abstract is too short that it lacks the essential contents, including context/purpose (1-2 sentences), methods (1-2 sentences), results (3-4 sentences), interpretations (3-4 sentences), and conclusion (1-2 sentences).

Response: Thanks for your question. The abstract part of the article has been revised and the relevant content has been added.

The abstract has improved; however, the reviewer suggests that the authors revisit each sentence as there is a better way of expressing the authors' thoughts.

Response: Thanks to the reviewer's reminding, the author rewrote some of the sentences.

 

Point 2: The introduction does not provide a good research background/solid rationale/argument of why the current study is crucial. It does not explicitly emphasize the research gap from the previous works stated.

Response: Thank this reviewer for reminding this point. At the beginning and end of the introduction section of the revised article, the importance of the study and the difference from previous studies are emphasized.

The introduction has improved; however, the reviewer suggests that the authors revisit each sentence as there is a better way of expressing the authors' thoughts.

Response: Thanks for the reviewer's valuable comments, the author has modified the sentences marked by the reviewer.

 

Point 3: The materials and methods section is also poorly written. The reviewer thinks that the moisture content of tailings should be generally higher near the release point. Kindly clarify this idea. For Figures 2 and 3, kindly replace the y-axis to % passing finer and reverse the values in the x-axis. Consider marking d10, d30, d50, and d60 also. Kindly make sure to use appropriate nomenclatures/symbols. At what depth were the samples collected? Kindly explicitly state if the samples collected were disturbed or undisturbed samples. Likewise, kindly explicitly specify or use the terms remolded and (or) reconstituted specimens. Also, kindly explicitly mention that the study employed a triaxial test scheme. Why UU test? Kindly classify the samples according to USCS or AASHTO, whichever is more appropriate based on the application field. What was the basis for the values presented in Tables 2 and (or) 3?

Response: Thanks for your question. Because water in Chengchao Iron Mine will converge in the place far away from the ore drawing mouth along with seepage, the water content will be higher the farther away from the ore drawing mouth.

The reviewer appreciates the authors' response. On the other hand, the reviewer believes that, as water flows from the discharge point to any channel path, there could be some water loss. It is also assumed by the reviewer that there is a continuous accumulation of water during the discharge; hence, the possibility of wetter conditions near the discharge point is possible.

Response: Thank you very much for the questions raised by the reviewers. This phenomenon will be further studied in the subsequent experiments.

The gradation experiment is only to prove the poor gradation of the test materials, so the author believes that it is not necessary to replace the ordinate coordinate more carefully, and the abscissa represents the particle size of sand by logarithmic coordinate, which is also the method adopted in most papers. The inverse transfer of the ordinate result in an unintuitive image. The various gradation parameters have been listed in Table 2 for easy access to the data.

Is the mass percentage retained or passing? Also, instead of using (/) to indicate a unit, kindly use () instead (e.g., (%)).

Response: Thank the reviewer for mentioning this problem. The quality percentage is retained. The author corrects the unit of the original image in the attachment.

 

Samples were collected at a depth of 40cm and the samples collected were undisturbed, and these questions have been supplemented in the test material section in the modified article.

Where in section 2, the authors specified that the samples collected were undisturbed? Were the samples really undisturbed? How were the samples retrieved (i.e., sampling method)? On the one hand, the reviewer believes that the authors collected disturbed samples from the test site and remolded these samples in the lab for strength and permeability testing.

Response: Thank you very much for the author's reminding. The samples were collected in the field and tested in the laboratory. In this respect, the samples were indeed disturbed.

 

The shear strength index of triaxial test should conform to the actual state as far as possible. The unconsolidated and undrained test is suitable for saturated tailing sand with small permeability coefficient, and the total stress shear strength index can be measured by the unconsolidated and undrained test.

The reviewer, on the other hand, believes that since most of the sands were classified as poorly graded sands, the permeability may not be as low as the authors believe. Kindly think of a better argument for why UU triaxial test is appropriate for the current study. Consider short-term or long-term dam stability analysis.

Response: Thanks for the reviewer's question, the authors combed the test conditions again, and found that the test was consolidation undrained test. And the consolidation undrained test is more consistent with the corresponding stress condition of tailing ore.

 

The Cc and Cu in Table 3 are adjusted for the grading according to the particle size of the sample taken by controlling one of the variables to change the other.

The reviewer accepts this response.

 

Point 5: Kindly consider a more appropriate term for the particle size range (i.e., with a narrow range) rather than single-particle size.

Response: Thank this reviewer for reminding this point. A single particle size refers to a certain particle size interval. In this paper, unconsolidated and undrained shear tests were carried out for tailings sand in the interval of less than 0.075mm, 0.075-0.1mm, 0.1-0.25mm, 0.25-0.5mm and 0.5-1mm, respectively. In order to avoid the reader's misunderstanding, the author has made corrections in the article.

The reviewer accepts this response.

 

 

 

Point 6: What is the definition of stress at failure for the triaxial UU test results? Is it peak stress or residual stress? Or is it at some axial strain when the stress-strain curve does not explicitly show a peak or residual stress?

Response: Thank this reviewer for reminding this point. Due to the triaxial test under the condition of single particle size, for the sample with relatively uniform particle size, the stress-strain curve belongs to an elastic-plastic curve, which does not obviously show the peak stress or residual stress.

The authors did not explicitly answer the reviewer's concern.

Response: Thanks for the reviewer's question. The stress during triaxial test failure is defined as residual stress.

 

Point 7: The reviewer is confused about the permeability test performed by the authors. The reviewer suggests explicitly explaining the details of the test.

Response: Thank this reviewer for reminding this point. The test method for the percolation section has been supplemented to the article.

The reviewer's concerns remain.

Response: Thanks for the reviewer's suggestion. In the penetration part, the author rejoined the interface of software operation. The author hopes to increase the understanding of readers and reviewers in this way.

 

Point 8: When the specimens subjected to a UU triaxial test are saturated (i.e., S = 100%), the Mohr-Coulomb failure envelope is generally horizontal, which means that the Mohr’s circle, regardless of the applied confining pressure, does not grow, but will only translate. Hence, the reviewer is skeptical about the results presented in the current study.

Response: Thank this reviewer for reminding this point. The phenomenon you mentioned does exist in cohesive soil. Foundation soil is composed of gas phase, liquid phase and solid phase. In a strict sense, saturated soil means that the voids in the soil are filled with water. However, the geotechnical test shows that the saturation of the soil is generally difficult to reach 100%, but the B value is above 0.95, and we also think that the soil is saturated. So the internal friction angle you see is not 0.

The reviewer agrees that the soil medium is a three-phase system. Regardless of the soil type, if it is pure (i.e., without any additives), a UU test would not yield friction angles as high as those reported in the current study. There might be some systematic errors during the testing. The reviewer suggests revisiting the test protocols. If the authors insist their results are reasonable, the reviewer suggests comparing them to previous studies.

Response: Thanks for the questions raised by the reviewers, the authors have sorted out the experimental process again, and explained it from the following three aspects:

1. The test uses sand instead of soil, and its mechanical properties are different from those of saturated clay.
2. The saturation test of tailing sand is carried out because the sand samples taken are below the infiltrationline, so the test under saturation condition is more in line with the actual situation. However, the saturation cannot reach 100% with the existing test conditions, but can reach more than 97%, which can be approximately considered as saturation state.
3. The authors sorted out the test conditions again and adopted consolidation and undrained test instead of unconsolidated and undrained test, which was caused by the authors' mistake in statistical data. The consolidation and undrained test is more consistent with the stress of tailing sand, and the corresponding internal friction Angle is also consistent with the general experimental law.In the CU test under saturation condition, the internal friction Angle of the tailing sand is consistent with the test law.

 

Point 9: The reviewer also has reservations about the reported hydraulic conductivity values, as the test program needs to be discussed in detail.

Response: Thank this reviewer for reminding this point. The authors supplemented the methodology of the trial in the infiltration assay.

The reviewer suggests elaborating on why the hydraulic conductivity was not significantly affected by the change in particle gradation.

Response: Thank you very much for your reminding. The author believes that because the three gradations selected have good mechanical properties, fine particles will fill the pores between coarse particles, so the numerical difference is not obvious, and has made explanations in the paper.

 

Point 10: The results section is written poorly. Likewise, there are no discussions provided nor comparison or benchmarking of results from previous works. The reviewer suggests avoiding listing or enumerating the observations using numerals. Write in paragraph form.

Response: Thank this reviewer for reminding this point. The authors have revised these results in the original text.

The reviewer's concerns remain. The reviewer strongly suggests comparing the results of the current study to previous and relevant studies to enrich the discussion and fully realize the scientific contribution of the conducted research. The lack of comparison or benchmarking is one reason why there are not enough cited references that helps the reviewer position the findings of the current study.

Response: Thanks for the reviewer's suggestion. At the end of the research results, the comparative analysis with the previous test results was added, emphasizing the significance of the test.

 

Point 11: Cite more relevant papers. Follow the correct format when citing references also. Likewise, follow the correct format when listing references. Make sure to complete all sections after the conclusion part.

Response: Thank this reviewer for reminding this point. The authors have increased the number of references cited and have also modified the format of other documents. The authors supplemented the missing parts as requested.

The reviewer's concerns remain. The listed references do not conform to the journal's format.

Response: Thank you very much for the reviewer's concerns. Because there are many kinds of references, including journals, dissertations and various standards, the issue number and page number of some references cannot be provided. The author has highlighted the issue title and the year number of the publication.

 

Point 12: Follow the correct style or format when listing authors and their affiliations.

Response: Thank this reviewer for reminding this point. At the beginning of the article, I have made changes to the format.

The reviewer suggests including the region or country (i.e., China) in the authors' complete affiliation address.

Response: Thank you very much for the reviewer's reminding. This problem has been modified in the article.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors responded to most of my questions. In my opinion the work is suitable for publication in Applied Sciences.

Author Response

Thank you very much for the reviewer's affirmation of the author's experiments and conclusions, and thank you for your valuable suggestions on the article.

Reviewer 3 Report

The reviewer has carefully checked the manuscript again. Although the manuscript was revised, it contains strange results which are far from our general knowledge. The reviewer cannot confirm the consistency between description in the text and test results. The reviewer insists "saturated" should not be used in the manuscript because of the following problems.

 

1. Related to the comment 7: The reviewer cannot understand how the specimens were created for the tests. From the manuscript, wet sand seems to be used. Was wet sand compacted to achieve the target dry density (Wet tamping method)? However, if this method was used, it is difficult to get saturated specimen without additional special treatments for saturation. If the degree of saturation is 97%, it is not saturated specimen. B-value must be less than 0.95. The reviewer doubts the measuring method of B-value.

 

2. Related to the comment 8: If saturated soils were used, phi should be zero in the Fig. 9. Therefore, the reviewer insists the specimens used are not saturated state (B-value is less than 0.95).

 

3. Related to the comment 9: c' and phi' are used for effective stress expression. Don't use c' and phi' because the authors have not used the effective stress.

 

Author Response

The reviewer strongly recommends availing of English editing services or carefully proofreading the paper.

The reviewer has carefully checked the manuscript again. Although the manuscript was revised, it contains strange results which are far from our general knowledge. The reviewer cannot confirm the consistency between description in the text and test results. The reviewer insists "saturated" should not be used in the manuscript because of the following problems.

1. Related to the comment 7: The reviewer cannot understand how the specimens were created for the tests. From the manuscript, wet sand seems to be used. Was wet sand compacted to achieve the target dry density (Wet tamping method)? However, if this method was used, it is difficult to get saturated specimen without additional special treatments for saturation. If the degree of saturation is 97%, it is not saturated specimen. B-value must be less than 0.95. The reviewer doubts the measuring method of B-value.
2. Related to the comment 8: If saturated soils were used, phi should be zero in the Fig. 9. Therefore, the reviewer insists the specimens used are not saturated state (B-value is less than 0.95).
3. Related to the comment 9: c' and phi' are used for effective stress expression. Don't use c' and phi' because the authors have not used the effective stress.

 

Response: Thanks for the questions raised by the reviewers, the authors have sorted out the experimental process again, and explained it from the following three aspects:

1. The test uses sand instead of soil, and its mechanical properties are different from those of saturated clay.
2. The saturation test of tailing sand is carried out because the sand samples taken are below the saturation line, so the test under saturation condition is more in line with the actual situation. However, the saturation cannot reach 100% with the existing test conditions, but can reach more than 97%, which can be approximately considered as saturation state.This issue is already explained in the text;
3. The authors sorted out the test conditions again and adopted consolidation and undrained test instead of unconsolidated and undrained test, which was caused by the authors' mistake in statistical data. The consolidation and undrained test is more consistent with the stress of tailing sand, and the corresponding internal friction Angle is also consistent with the general experimental law.In the CU test under saturation condition, the internal friction Angle of the tailing sand is consistent with the test law.

 

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

The reviewer appreciates the immediate action taken by the authors to address the comments and suggestions raised during the second round of the review process. Kindly find the commented latest version of the manuscript.

Overall, the manuscript has improved. However, the reviewer suggests that the authors observe consistency throughout the paper. Unfortunately, the authors indicated that the triaxial test performed was UU and suddenly realized that it was not, but rather a CU. The reviewer suggests that this mistake will not happen next time and that the authors should be more careful before submitting a paper to any journal. Thus, peer review and scrutiny are needed to avoid these errors before a paper is published.

Likewise, the tone and writing style can still be improved to make the paper more concise and readable. Moreover, the reviewer suggests using high-resolution graphs with legible texts and (or) labels. The reviewer also suggests that authors check other papers published in Applied Sciences of any MDPI journal about formatting style.

Comments for author File: Comments.pdf

Author Response

Thanks for the reviewer's comments on the article. The author has corrected these problems in the article.

Regarding the picture in the article, the author has uploaded the original image in the attachment.

In the file uploaded by the author, the letters in the table are not capitalized and the format is correct.

Author Response File: Author Response.pdf

Reviewer 3 Report

We have a hard time communicating. The reviewer cannot understand the authors' insistence well. The readers also seem to have the same problems. Therefore, the same issues remain again as follows. 

 

1. Related to the comment 1: Please describe the specimen preparation method to achieve the target dry density of 1.68 g/cm3. If the authors have used undisturbed samples, please mention it in the text.

 

2. Related to the comment 1: The reviewer has considered moisture content of 15% in Tables 3 and 4 is used for specimen preparation. The moisture content changes during the testing. Please specifically describe what situation is considered for moisture content of 15%, e.g., specimen preparation, after the consolidation, or after the testing?

 

3. Related to the comment 3: c' and phi' are used in Table 5. Don't use c' and phi' because the authors have not measured pore water pressure during undrained shearing.

 

Author Response

We have a hard time communicating. The reviewer cannot understand the authors' insistence well. The readers also seem to have the same problems. Therefore, the same issues remain again as follows.

 

1. Related to the comment 1: Please describe the specimen preparation method to achieve the target dry density of 1.68 g/cm³. If the authors have used undisturbed samples, please mention it in the text.

Thanks to the reviewers for the question. Dry density is derived by calculation. The calculation method of dry density is explained in the third part. Firstly, the wet density of sample is calculated by dividing the wet soil mass by the ring cutter volume, and then the dry density of sample is calculated by the formula. The sample was disturbed during sampling.

 

2. Related to the comment 1: The reviewer has considered moisture content of 15% in Tables 3 and 4 is used for specimen preparation. The moisture content changes during the testing. Please specifically describe what situation is considered for moisture content of 15%, e.g., specimen preparation, after the consolidation, or after the testing?

Thanks to the reviewers for the question. The test was carried out at saturation and the water content measurements were made in order to derive the dry density of the sample using the formula.

 

3. Related to the comment 3: c' and phi' are used in Table 5. Don't use c' and phi' because the authors have not measured pore water pressure during undrained shearing.

Thanks for the reviewer's reminding, the author did not calculate the pore water pressure, and the measurements were not effective cohesion and internal friction Angle, which have been modified in the paper.

Round 4

Reviewer 3 Report

The authors' responses are insufficient again this time.  Therefore, it is difficult to discuss moreover.

Author Response

Related to the comment 1: Please describe the specimen preparation method to achieve the target dry density of 1.68 g/cm³. If the authors have used undisturbed samples, please mention it in the text.

Thanks again to the reviewer's comments, the moisture content w=15% was measured in the moisture content test, in order to reach the dry density = 1.68g/cm³, using the formula , the wet density of the specimen can be calculated= 1.932g/cm³, and the wet density is calculated using the method of dividing the wet soil mass m by the ring knife volume v, the formula is =, the ring knife volume v=200cm³ used in the triaxial test, we can conclude that the wet soil mass is m=386.4g. So we only need to control the mass of wet soil to achieve the target dry density. The authors have added the preparation method to reach the target dry density to the article.

The formula cannot be entered into the dialog box. Please review it in the file.

Related to the comment 1: The reviewer has considered moisture content of 15% in Tables 3 and 4 is used for specimen preparation. The moisture content changes during the testing. Please specifically describe what situation is considered for moisture content of 15%, e.g., specimen preparation, after the consolidation, or after the testing?

Thanks again for the reviewer's question, the 15% moisture content is the moisture content at the time of specimen preparation, in other words, the 15% moisture content is the moisture content before the specimens are saturated for the triaxial test, the specimens are saturated and the moisture content after the test has not been measured by the authors. The authors have made notes in the text for Tables 3 and 4.

 

Related to the comment 3: c' and phi' are used in Table 5. Don't use c' and phi' because the authors have not measured pore water pressure during undrained shearing.

Thanks for the reviewer's reminding, the author did not calculate the pore water pressure, and the measurements were not effective cohesion and internal friction Angle, which have been modified in the paper.

Author Response File: Author Response.pdf