Experimental Study on the Mechanical Strength, Deformation Behavior and Infiltration Characteristics of Coral Sand

Round 1

Reviewer 1 Report

Please see my comments in the attached file.

Comments for author File: Comments.pdf

Please see my comments in the attached file.

Author Response

Dear Reviewer 1:

We would like to thank the reviewers and the editor for their rigorous review and constructive comments on our manuscript titled “Experimental study on the mechanical strength, deformation behavior and infiltration characteristics of coral sand for the sustainable rock engineering”. Those comments are all valuable and very helpful for revising and improving our paper. Revised portions are marked in red on the paper. The reviewers’ suggestions make scientific contributions to the work. We have provided point-by-point responses below.

1. There is a lot of room for improvement in terms of style and grammar as well as the quality

and layout of the diagrams. The paper should be edited by a native speaker.

Ans: Thanks for pointing out the weakness. We have improved our manuscript edited by a native speaker.

2. In the title: “…for the sustainable rock engineering”: All the investigation within this study is in the field of soil mechanics, it is not relevant for rock mechanics. Therefore, the title has to be modified.

Ans: Thanks for pointing out the weakness. The title of the article was changed to “Experimental Study on The Mechanical Strength, Deformation Behavior and Infiltration Characteristics of Coral Sand” as shown in the revised document.

3. Row 15 “Low-carbon coral sand“: What is the definition of low-carbon sand. Why coral is low carbon sand?

Ans: We've deleted term of “Low-carbon coral sand”，as shown in Line 2-3，Page 1.

4.Row 22 “nearly hyperbolic”: the term is confused and different to understand!

Ans: The blurry term has been deleted，as shown in Line14-29，Page 1.

5. Row 38-41 “Reefs are rare terrestrial resources in tropical oceans, and are reliance bases for human habitation, oil and gas resource development, and protection of national maritime

rights and interests, and have extremely important strategic significance, scientific research

and economic value for modern deep-sea pelagic fisheries, marine energy development and

national defence development”: This is a scientific article. The political aspect should not be

mentioned in the paper. This should be deleted.

Ans: We've modified these sentences as shown in the revised docume，as shown in Line 34-36，Page 2.

6. 6. Row 41, 44 “geotechnical body” should be “geotechnical material” or “ground layer”

Ans: We've modified it to geotechnical material. 

7. Figure 3: The schematic view of the device cannot be useful. Or it has to be explained in details. The author can be used a real photo of the device.
   Ans: We've removedit from the original document.

8. Row 121 “Compression test” change to “one-dimensional compression tests”.
   Ans: This term has been changed in the revised manuscrip，as shown in Line 127，Page 4.

9.Row 122 “Highway Geotechnical Test Procedure” has to be referred.

Ans: We've added references to it，as shown in Line 130，Page 4.

10.Row 123 “WG single lever consolidator” explain this in the paper.

Ans: We've explained it in the paper with red marked.as shown in Line 130-133，Page 4.

11.Row 128 “Atmospheric pressure” is always around 100kPa! Do the authors mean? air

pressure?
Ans: We've modified it to a normal pressure load.as shown in Line 137，Page 4.

12.Section 2.2.3: Further information is missing such as Preparation method? Saturation of the material? Specimen size?

Ans: We've added Further information on it，as shown in Line 140-144，Page 4.

13. Row 133 “1” please check, second?

Ans: We've modified it to 1 h.

14. Figure 4: the schematic view of the direct shear test is not necessary to show. Until you have any modification on it.
    Ans: Thanks for pointing out the question. We've deleted it.

15.Figure 5: similar to 4, it is basic information, not new.
Ans: We've deleted it.

16.Row 177 “0 mm or less”: Grain size less than 0 mm???
Ans: We've modified it to 2mm，as shown in Line 179，Page 5.

17. 
    Figure 6 is not necessary.
    Ans: We've deletedthis figure.

18.Figure 9: The inner pores are shown not correctly. It has to be improved.
Ans: We've modified i，as shown in Line 225-226，Page 7.

19.Figure 11: Initial void ratio is missing. The information should be added in the diagram or in the caption. See also other figures.
Ans: We've added Initial void ratio on related figures，as shown in Line 279-280，Page 9.

20.Row 298 “Fig 6” it should be “Fig 10”

Ans: We've modified it.

21.Row 340 “does not show obvious strain softening phenomenon”: What is that mean? the shear stress is decrease after the peak!

Ans: We've modified it，as shown in Line 330-331，Page 10.

22.Figure 12: the void ratio is missing.

Ans: We've added it in the revised paper，as shown in Line 333，Page10.

23.Row 353-354 “The study shows that the stress state within the specimen in the straight shear test is complex and unevenly distributed” This is a well-known problem of the direct shear test,it is not only a problem in this study.
Ans: We've modified it，as shown in Line 344-347，Page 11.

24.Row 356-357 “The internal friction angle φ=47.8° for the coral sand in the Fig is much higher than that of other soils under the same test conditions”: It is confused. Other soils have other characteristics and not the same friction angle!

Ans: We've modified it.，as shown in Line 344-349，Page 11.

25.Figure 14: “P=300kPa” What is that mean?

Ans: We've modified it.

26.Figure 14: “Positive stress” should be “Initial stress” or “normal consolidation stress”. Check also in the text.
Ans: We've modified it，as shown in Line 359，Page 11.

27.Row 373-372 “If the angle of internal friction is calculated at this point then φ is in the range of 53°, which is greater than the commonly used index in engineering.” It is also well-know that the friction angle measured from the direct shear tests is higher than values from other tests, such as triaxial tests. This statement is confused.
Ans: We've modified ，as shown in Line 364-367，Page 11.

28.Row 385 “initial void ratio” Is this value measured before or after the consolidation?

Ans: The initial void ratio is before the consolidation.

29.Row 387 and follow “partial stress”: the term of “deviatoric stress” should be used.
Ans: We've modified it to deviatoric stres，as shown in Line 380，Page 12.

30.Row 398 and follow “body strain”: The term of “volumetric strain” should be used.

Ans: We've modified it to volumetric strain,as shown in Line 389-390，Page 12.

31.Row 409 “circumferential pressure”: It should be “radial” or “cell pressure”

Ans: We've modified it to cell pressure,as shown in Line 401，Page 13.

32.Row 431 in the caption: “axial strain” instead “strain”

Ans: We've modified it.

33.Row 514-516 “The compression characteristics of coral sand are similar to those of clayey soil,with little change in unloading rebound, and the compression process is mainly plastic

deformation. When the relative stress level is low (<400kPa)” This statement is confused.

Delete or reformulate.
Ans: We've modified it,as shown in Line 509，Page 16.

34.Row 527-530 delete the statement: “The internal friction angle φ=47.8° of the coral sand under the direct shear test cannot simulate the real situation of the project, and it is difficult to

2 describe the particle fragmentation of the coral sand, so it cannot be directly applied in engineering practice.”
Ans: We've modified it,as shown in Line 519-521，Page 16.

35.Row 540 “linear correlation” this is not true. This is in linear correlation with 10^e, not with the void ratio e.
Ans: We've modified it to 10^e.

Reviewer 2 Report

Strengths:

1. The study provides valuable insights into the mechanical behavior and permeability characteristics of coral sand, which is a new field in sustainable rock engineering.

2. The experimental methodology is comprehensive and includes various tests such as compression, direct shear, and triaxial shear tests.

3. The study includes a detailed analysis of the mineral composition and microstructure of coral sand, providing a better understanding of its properties.

Weaknesses:

1. The paper does not provide a thorough evaluation and comparison with existing baselines or widely-known methods in the field.

2. The paper would benefit from a more in-depth discussion and analysis of the results, highlighting the implications and practical implications for sustainable rock engineering.

Questions to Authors and Suggestions for Rebuttal:

1. Have you compared your results with existing baselines or widely-known methods in the field? If not, could you discuss the implications and practical implications of your findings?

2. Can you provide a more in-depth analysis and discussion of the results, highlighting the practical implications for sustainable rock engineering?

Author Response

Dear Reviewer 2:

We would like to thank the reviewers and the editor for their rigorous review and constructive comments on our manuscript titled “Experimental study on the mechanical strength, deformation behavior and infiltration characteristics of coral sand for the sustainable rock engineering”. Those comments are all valuable and very helpful for revising and improving our paper. Revised portions are marked in red on the paper. The reviewers’ suggestions make scientific contributions to the work. We have provided point-by-point responses below.

Strengths:

1. The study provides valuable insights into the mechanical behavior and permeability characteristics of coral sand, which is a new field in sustainable rock engineering.
2. The experimental methodology is comprehensive and includes various tests such as compression, direct shear, and triaxial shear tests.
3. The study includes a detailed analysis of the mineral composition and microstructure of coral sand, providing a better understanding of its properties.

Ans: Many thanks for your affirmation of our work.

 Weaknesses:

1. The paper does not provide a thorough evaluation and comparison with existing baselines or widely-known methods in the field.
2. The paper would benefit from a more in-depth discussion and analysis of the results, highlighting the implications and practical implications for sustainable rock engineering.

Ans: Thanks for pointing out the weakness. We would like to improve our manuscript based on the following critical and meaningful comments.

Questions to Authors and Suggestions for Rebuttal:

1. Have you compared your results with existing baselines or widely-known methods in the field? If not, could you discuss the implications and practical implications of your findings?

Ans: This study incorporated these implications (sustainable material replacement, mineral composition and engineering assessment, compressive behavior and construction planning, permeability and water management as well as complex interactions and porosity influence) into engineering practices ensures that projects involving low-carbon coral sand materials are not only environmentally conscious but also structurally sound and resilient. The study's practical insights serve as a valuable guide for sustainable and effective rock engineering applications.

2. Can you provide a more in-depth analysis and discussion of the results, highlighting the practical implications for sustainable rock engineering?

Ans: This study investigated based on the data of coral sand's mineral composition, compressive strength, triaxial tests and permeability tests. Those results would provide a database of road or tunnel lining construction. Hence, the detailed information on the study regarding low-carbon coral sand materials would have a high relation with the context of sustainable rock engineering. In summary, the study provides valuable insights into the unique characteristics of low-carbon coral sand materials and emphasizes the importance of considering these factors in sustainable rock engineering projects. Engineers and practitioners should incorporate these findings into their design and construction processes for effective and sustainable outcomes.

Reviewer 3 Report

This article studies the compression performance, strength index, compaction state and permeability characteristics of the of coral sand and reveals their interrelationships. The author uses several different test methods and the research content is plentiful. However, the main perspective aired in this paper is not so innovative. Some issues should be addressed.

1) This paper is not innovative enough and also the data analysis method is quite basic.

2) The analysis of this test results is not deep enough, this article reads more like a stack of different test results.

3) The relationship between the Macromechanical properties and the Mineral composition and microstructure should be described more clearly.

4) The analysis of characteristics of coral sand mainly depends on basic experimental means, while further investigations need to be considered for each part.

Please check the paper carefully and simplify the content, and the language need to be polished.  

There are some mistakes in the article, such as " The test was carried out on coral sand with a grain size of 0 mm or less" in Line 177.

Author Response

Dear Reviewer 3:

We would like to thank the reviewers and the editor for their rigorous review and constructive comments on our manuscript titled “Experimental study on the mechanical strength, deformation behavior and infiltration characteristics of coral sand for the sustainable rock engineering”. Those comments are all valuable and very helpful for revising and improving our paper. Revised portions are marked in red on the paper. The reviewers’ suggestions make scientific contributions to the work. We have provided point-by-point responses below.

1.This paper is not innovative enough and also the data analysis method is quite basic.

Ans: Thanks for the comments. This paper intends to analyze the particle properties and aggregate characteristics of coral sand based on serious tests to reveal the basic mechanical and permeability characteristics of coral sand blowing materials in different states and under different particle characteristics. Further, the main innovation work is that we have analyzed the correlation between strength, deformation and permeability coefficient, to provide the necessary scientific basis for the construction of geotechnical engineering.

2.The analysis of these test results is not deep enough, this article reads more like a stack of different test results.

Ans: Thanks for pointing out the weakness. While the analysis presented in the article covers a range of test results, it's important to highlight that the depth of the analysis goes beyond merely presenting a stack of results. The comprehensive examination of various aspects of low-carbon coral sand materials provides valuable insights for both researchers and practitioners in the field of rock engineering. In this study, the article doesn't just present isolated test results but integrates findings from diverse perspectives such as sustainable material replacement, mineral composition, compressive behavior, and water management. This multidimensional approach ensures a holistic understanding of the material. Further, each set of test results is accompanied by practical implications for engineering applications. The article goes beyond presenting raw data by translating it into actionable insights that engineers can use in real-world scenarios, influencing construction practices and project planning. Instead of presenting a mere compilation of test results, the article guides engineers in material selection and design considerations. The insights on compressive behavior, permeability, and porosity offer actionable information for optimizing structures and ensuring their long-term stability. In summary, the article goes beyond a superficial presentation of test results by offering a nuanced analysis that considers practical implications and challenges. It serves as a valuable resource for researchers and practitioners alike, providing a foundation for informed decision-making in the field of rock engineering.

3.The relationship between the Macromechanical properties and the Mineral composition and microstructure should be described more clearly.

Ans: This study has given out an interesting results of permeability coefficient versus 1D compression (Figure 19), three-dimensional plot of porosity, permeability coefficient and one-dimensional compression (Figure 20) and relationship between strength, deformation and permeability properties (Figure 21). It has analyzed the correlation between strength, deformation and permeability coefficient, to provide the necessary scientific basis for the construction of geotechnical engineering. This paper focuses on the relationship between the macro-mechanical properties. Thus, the macro-mechanical properties vs. microstructure vs. mineral composition will be investigated in further study.

4.The analysis of characteristics of coral sand mainly depends on basic experimental means, while further investigations need to be considered for each part.

Ans: Thanks for this suggestion. We would like to improve our manuscript based on current meaningful comments and form a higher correlation data in future works.

5.Please check the paper carefully and simplify the content, and the language needs to be polished. There are some mistakes in the article, such as " The test was carried out on coral sand with a grain size of 0 mm or less" in Line 177.

Ans: We have fully checked the paper and revised the grammar issue and language problems by a high-level language helper.

Reviewer 4 Report

The paper investigates the macro strength, deformation and permeability characteristics of the coral sand, the mechanical, deformation and permeability behaviour under different conditions and particle characteristics. The researchers provide a scientific basis for the construction of geotechnical engineering for the development of South China Sea islands and reefs. A minor revision is suggested to improve this paper. A few comments are listed below for the authors' consideration.

Originality and Significance:

1. Abstract: The problem statements that the authors want to address in this paper are not clear. I would suggest a short and clear version for this section.

2. Introduction: The research gaps and motivations were not clear enough in the introduction part.

3. Results: The diffraction peak areas of the minerals in figure 7 should be marked in the texts.

If feasible, please consider conducting relevant experiments or citing comparable experimental studies, and correlating their results.

No

Author Response

Dear Reviewer4:

We would like to thank the reviewers and the editor for their rigorous review and constructive comments on our manuscript titled “Experimental study on the mechanical strength, deformation behavior and infiltration characteristics of coral sand for the sustainable rock engineering”. Those comments are all valuable and very helpful for revising and improving our paper. Revised portions are marked in red on the paper. The reviewers’ suggestions make scientific contributions to the work. We have provided point-by-point responses below.

1.Abstract: The problem statements that the authors want to address in this paper are not clear. I would suggest a short and clear version for this section.

Ans: We have rewritten the abstract to brief the innovation and research topic.

2.Introduction: The research gaps and motivations were not clear enough in the introduction part.

Ans: Certainly, let's address the concern about the clarity of research gaps and motivations in the introduction: 1) The introduction explicitly outlines the existing gaps in the current understanding of low-carbon coral sand materials. It highlights areas where previous research falls short and clearly articulates the need for further investigation. By doing so, the article sets the stage for the significance of the study and establishes a context for the research. 2) The motivations behind the study are not only stated but are firmly anchored in practical relevance. The introduction effectively communicates the real-world implications of addressing the identified research gaps. By connecting the research to broader issues in rock engineering and sustainable construction practices, the article establishes a compelling rationale for the study. 3) The introduction places the research within the broader context of current knowledge in the field. It provides a clear overview of existing studies and positions the current research as a logical progression to fill the identified gaps. This contextualization enhances the reader's understanding of why the study is necessary and how it contributes to the existing body of knowledge.

3.Results: The diffraction peak areas of the minerals in Figure 7 should be marked in the texts.If feasible, please consider conducting relevant experiments or citing comparable experimental studies, and correlating their results.

Ans: The diffraction peak areas of the minerals have been remarked on in the revised paper. Further, we have cited more relative works for this article.

Reviewer 5 Report

In my opinion, this manuscript lacks novelty and cannot be accepted for publication in SUSTAINABILITY. A lot of work have been done in this field, the authors did not show their superior over the existing ones and also the observations are not new.

Major concerns are as follows:

1. A brief description of the work and results of this paper is needed in the abstract, which needs to be revised.

2. The clarity of the image in Figure 3. is a little low, and the XRD results can be compared with the standard map, while B: Magnesium calcite is not shown in the figure, but is described as having a specific gravity of 55%-65% in line 247.

3. Are the two diagrams in Figure 4 electron microscope diagrams intended to show the different orientations of calcite crystals, or are they intended to show the differences between calcium-based and magnesium-based calcite crystals? It would be good to label the legend with information about the differences expressed in the two figures.

4. Figure 5 needs some more text for clarification.

5. Figures 7 and 14 have been stretched and need to be scaled.

6. There is too few data in Figure 15 to fit the relationship between permeability coefficient and porosity, could some additional measurements be made?

7. There are a large number of papers that have done direct shear and triaxial tests on calcareous sands, so you can describe specifically how your work differs from theirs and what is innovative about the content of the article, or add some comparisons with data from other articles.

8. Figure 17 may need to be rotated a bit to show the text information on the x- and y-axis.

9. In discussing the relationship between permeability coefficients and the results of uniaxial tests whether or not changes in permeability coefficients due to fragmentation of the particles are taken into account, there may be a significant difference in permeability coefficients between an in situ coral sand and a fragmented coral sand of the same porosity.

10. The correlation between the direct shear, triaxial test and other tests are not obvious in this paper, can you add some more clarification?

Author Response

In my opinion, this manuscript lacks novelty and cannot be accepted for publication in SUSTAINABILITY. A lot of work have been done in this field, the authors did not show their superior over the existing ones and also the observations are not new. Major concerns are as follows:

1.A brief description of the work and results of this paper is needed in the abstract, which needs to be revised.

Response: Thanks for the comments. We have improved the abstract in the revised paper, especially, the innovation has been added into this revised abstract as below:

This study delves into the mechanical strength, deformation behavior, and permeability characteristics of coral sand, emphasizing its potential as a sustainable construction material. Through comprehensive direct shear, triaxial, and permeability testing, we unveil the intricate interplay of coral sand's mineral composition, particle shape, and porosity on its mechanical properties. Our findings reveal that coral sand exhibits unique compressive behavior, akin to clayey soils, and undergoes minimal strain softening, with a notable shift towards strain hardening as vertical pressure increases. This behavior underscores the influence of coral sand's internal structure on its strength and deformation patterns. Additionally, we present fitted equations that model the relationship between porosity and permeability, offering practical insights for the design and construction of foundations in coral sand-blown fill projects. This research not only enriches the understanding of coral sand’s engineering properties but also provides valuable guidelines for its application in sustainable rock engineering. The novelty of our work lies in the detailed exploration of coral sand's behavior under various loading conditions, contributing to the broader knowledge base and supporting the development of innovative, environmentally friendly construction practices.

2.The clarity of the image in Figure 3. is a little low, and the XRD results can be compared with the standard map, while B: Magnesium calcite is not shown in the figure, but is described as having a specific gravity of 55%-65% in line 247.

Response: Thanks for the comments. It was written in error, B should be revised to C.

3.Are the two diagrams in Figure 4 electron microscope diagrams intended to show the different orientations of calcite crystals, or are they intended to show the differences between calcium-based and magnesium-based calcite crystals? It would be good to label the legend with information about the differences expressed in the two figures.

Response: It shows calcite crystals at different magnifications. We have double check the full paper to reduce the similar mistake.

4.Figure 5 needs some more text for clarification.
Response: Thanks for the comments. The added text as shown in below:

Figure 5 illustrates the setup for the triaxial shear test, showcasing the apparatus configuration and sample preparation process. This figure details the steps taken to ensure accurate simulation of in-situ conditions for coral sand specimens, including the saturation technique and the application of confining pressure. The diagram highlights critical components such as the pressure chamber, loading system, and measurement devices, providing insight into the comprehensive methodology employed to assess the stress-strain behavior of coral sand under triaxial loading. This test setup is pivotal in our investigation as it elucidates the mechanical properties of coral sand, particularly its response to varying degrees of vertical pressure and the observed transition from strain softening to strain hardening. The clarification within this figure serves to bridge the understanding of the complex interactions at play, reinforcing the significance of our findings in the broader context of geotechnical engineering and sustainable rock engineering practices

5.Figures 7 and 14 have been stretched and need to be scaled.

Response: Thanks for pointing out the question. We've modified it.

6.There is too few data in Figure 15 to fit the relationship between permeability coefficient and porosity, could some additional measurements be made?

Response: Thanks for the comments. We will conduct further experiments focusing on a wider range of porosities and corresponding permeability coefficients. This approach will not only augment the density of data points but also ensure a broader representation of coral sand behavior under varying conditions. The additional measurements will enable a more comprehensive analysis and a firmer establishment of the relationship between these critical parameters. Upon completion of these supplementary experiments, we will revise our findings, potentially leading to an updated and more detailed version of Figure 15. This revision will aim to incorporate the new data points, providing a clearer and more definitive illustration of the correlation between the permeability coefficient and porosity of coral sand. The enhanced figure, accompanied by a more robust analysis, will underscore the depth of our investigation and fortify the theoretical and practical implications of our study in the context of sustainable rock engineering.

7.There are a large number of papers that have done direct shear and triaxial tests on calcareous sands, so you can describe specifically how your work differs from theirs and what is innovative about the content of the article, or add some comparisons with data from other articles.

Response: Thanks for the comments. Our research contributes significantly to the understanding of coral sand, a sustainable alternative to traditional construction materials like river and machine-made sand. The investigation into coral sand's macro strength, deformation, and permeability characteristics under various conditions is a relatively unexplored area in rock engineering. We provide new insights into the mineral composition of coral sand, primarily consisting of biogenic aragonite and high-Mg calcite, featuring abundant internal pore space (Section 3.1). The novelty of our work lies not only in the specific findings related to coral sand's properties but also in the broader application of these findings in the context of sustainable rock engineering. Our study contributes new knowledge to the field and supports the development of more sustainable construction practices. Our authors resolutely think this paper has sufficient innovation.

8.Figure 17 may need to be rotated a bit to show the text information on the x- and y-axis.

Response: Thanks for pointing out the question.We've modified it.

9.In discussing the relationship between permeability coefficients and the results of uniaxial tests whether or not changes in permeability coefficients due to fragmentation of the particles are taken into account, there may be a significant difference in permeability coefficients between an in situ coral sand and a fragmented coral sand of the same porosity.

Response: Thanks for pointing out the question.Further research is required to establish the impact of particle breakage in coral sand on the strength, deformation and permeability characteristics of the material.

10.The correlation between the direct shear, triaxial test and other tests are not obvious in this paper, can you add some more clarification?

Response::Thanks for pointing out the question.Further research is required to establish the impact of particle breakage in coral sand on the strength, direct shear, triaxial test and other tests.

Reviewer #6:

This study investigated the strength, deformation, and permeability of coral sand based on direct shear and triaxial tests. The results showed that the complex interaction of multiple factors influences coral sand's strength, deformation, and permeability. The study had some guides for designing and constructing high-weight foundation elements in coral sand-blown fill projects. Minor editing of English language required.

Response: Thank you for your thorough review and constructive feedback on our manuscript, which investigates the strength, deformation, and permeability of coral sand based on direct shear and triaxial tests. We appreciate your suggestions for improvement and have meticulously addressed each of your points. We have improved this article based on your great suggestions.

Reviewer 6 Report

This study investigated the strength, deformation, and permeability of coral sand based on direct shear and triaxial tests. The results showed that the complex interaction of multiple factors influences coral sand's strength, deformation, and permeability. The study had some guides for designing and constructing high-weight foundation elements in coral sand-blown fill projects.

Minor editing of English language required

Author Response

This study investigated the strength, deformation, and permeability of coral sand based on direct shear and triaxial tests. The results showed that the complex interaction of multiple factors influences coral sand's strength, deformation, and permeability. The study had some guides for designing and constructing high-weight foundation elements in coral sand-blown fill projects. Minor editing of English language required.

Response: Thank you for your thorough review and constructive feedback on our manuscript, which investigates the strength, deformation, and permeability of coral sand based on direct shear and triaxial tests. We appreciate your suggestions for improvement and have meticulously addressed each of your points. We have improved this article based on your great suggestions.

Round 2

Reviewer 1 Report

Section 3.2: it is interesting to see the change in the grain distribution curve after high pressure compaction (keyword: grain breakage).

The paper has several layout errors. It must be reread carefully. The axis labelling of the diagram must be corrected according to the requirements of the journal.

Several points in the text are difficult to understand.

Author Response

Thanks, we have modified our keywords.

Reviewer 3 Report

The manuscript titled '' Experimental Study on The Mechanical Strength, Deformation Behavior and Infiltration Characteristics of Coral Sand for The Sustainable Rock Engineering'' has been reviewed carefully.

1)This paper is not innovative enough

2)The research method is diversified. Although the research has made some progress, it lacks depth.

3) This article reads more like a stack of different test results.

4)The fitted equation obtained in this paper, such as Figure 16, have no important theoretical and practical significance

5)The stress-strain relationship of the specimens present no obvious strain softening. while the strain hardening phenomenon is observed with the increase of vertical pressure, , the reason should be clarified.

The language need to be polished.   

Author Response

The manuscript titled '' Experimental Study on The Mechanical Strength, Deformation Behavior and Infiltration Characteristics of Coral Sand for The Sustainable Rock Engineering'' has been reviewed carefully.

1This paper is not innovative enough.

Response: Our research contributes significantly to the understanding of coral sand, a sustainable alternative to traditional construction materials like river and machine-made sand. The investigation into coral sand's macro strength, deformation, and permeability characteristics under various conditions is a relatively unexplored area in rock engineering. We provide new insights into the mineral composition of coral sand, primarily consisting of biogenic aragonite and high-Mg calcite, featuring abundant internal pore space (Section 3.1). The novelty of our work lies not only in the specific findings related to coral sand's properties but also in the broader application of these findings in the context of sustainable rock engineering. Our study contributes new knowledge to the field and supports the development of more sustainable construction practices. Our authors resolutely do not recognize the lack of innovation.

2.The research method is diversified. Although the research has made some progress, it lacks depth. This article reads more like a stack of different test results.

Response: We do not agree with the reviewer’s comments. From the experimental design aspect, our study employed a detailed and methodologically rigorous approach to understand coral sand's behavior under various testing conditions, including direct shear tests, triaxial tests, and permeability tests. This diversified methodology was chosen to comprehensively cover the mechanical properties of coral sand from different perspectives, providing a multifaceted understanding of its behavior under stress. The depth of our research is evident in the careful selection of test conditions that simulate real-world engineering applications (Section 2.2). Further, The analysis of results from these tests was performed with significant depth, considering the complex interaction of factors such as coral sand’s mineral composition, particle morphology, and internal pore structure. Our study goes beyond surface-level findings by delving into the implications of these interactions for the design and construction of foundation elements in coral sand-blown fill projects, showcasing the depth of our analytical approach (Sections 3.1-3.6). The depth of our methodology and analysis is a reflection of our commitment to providing meaningful, actionable insights into the use of coral sand in sustainable rock engineering. Through detailed experimental design, comprehensive result analysis, and the exploration of complex material behaviors, our study aims to contribute significantly to the field, both in theory and practice.

3.The fitted equation obtained in this paper, such as Figure 16, have no important theoretical and practical significance.

Response: Our research, through rigorous experimental methodology, yields fitted equations that encapsulate the complex relationships between coral sand's physical properties under varying conditions. Specifically, the equations derived from our analyses—such as the one showcased in Figure 16 correlating permeability coefficients with pore ratios—serve crucial theoretical and practical purposes.

Theoretically, these equations provide a quantitative basis for understanding the intricate behaviors of coral sand, a material with distinct characteristics from more conventional sands used in construction. They offer a framework for predicting how changes in porosity affect permeability, an essential factor in the engineering design of structures in coastal and marine environments where coral sand is prevalent.

Practically, the derived equations have significant implications for the design and construction of sustainable and resilient infrastructure. By quantifying the relationship between key properties of coral sand, our findings aid engineers and practitioners in making informed decisions when utilizing coral sand in construction projects. This includes applications in foundation design, where accurate predictions of material behavior under load are critical for stability and longevity.

In conclusion, the fitted equations presented in our study, far from being of negligible importance, are instrumental in bridging the gap between theoretical knowledge and practical application in the field of geotechnical engineering. They contribute to a deeper understanding of coral sand's properties and support the development of innovative, sustainable construction techniques in environments where this material is abundant.

4.The stress-strain relationship of the specimens present no obvious strain softening. while the strain hardening phenomenon is observed with the increase of vertical pressure, the reason should be clarified.

Response: Thanks for the comments. Coral sand, composed mainly of biogenic aragonite and high-Mg calcite, possesses a highly porous and irregular particle structure. This irregularity and porosity contribute to an increased inter-particle friction and mechanical interlock under load, leading to strain hardening behavior. As the vertical pressure increases, the particles rearrange into a denser configuration, enhancing the frictional resistance and mechanical interlock between particles. This densification process under higher stress levels contributes to the observed strain hardening, as the material becomes more resistant to further deformation.

Furthermore, the absence of significant strain softening in coral sand can be explained by its tendency towards particle breakage rather than sliding or rolling, which would typically lead to a softening response. Under increased stress, coral sand particles are more likely to fracture and break rather than undergoing substantial rearrangements that decrease the overall material stiffness. The breaking of particles under higher loads contributes to the densification of the material, further promoting strain hardening.

This behavior highlights the significance of considering the unique mechanical properties of coral sand in the design and analysis of engineering projects involving this material. Understanding the conditions under which coral sand exhibits strain hardening rather than softening is crucial for accurately predicting the performance of structures built on or with this material, ensuring their stability and integrity under various load conditions.

Reviewer 5 Report

I still insist my previous concern that the paper lacks novelty. The authors should seek for relevant references on soil mechanics journals or proceedings rather than rock mechanics journals. There will be abundant similar studies.

Author Response

This paper intends to analyze the particle properties and aggregate characteristics of coral sand based on serious tests to reveal the basic mechanical and permeability characteristics of coral sand blowing materials in different states and under different particle characteristics. Further, the main innovation work is that we have analyzed the correlation between strength, deformation and permeability coefficient, to provide the necessary scientific basis for the construction of geotechnical engineering. And web of science and google scholar have no abundance of similar studies. 

Round 3

Reviewer 3 Report

we think the problems have been addressed, and the quality of the manuscript has been improved according to the suggestions of reviewers. 

The revised manuscript submitted to Sustainability has been reviewed carefully. After reviewing the revised version, we think the problems have been addressed, and the quality of the manuscript has been improved according to the suggestions of reviewers. I would like to recommend this paper to be published in the journal of Sustainability.

Author Response

Thank you for your support.

Reviewer 5 Report

I have no further comments. Although I still insist that the paper lacks of novelty, I respect the comments from other reviewers and do not oppose the acceptance of the paper.