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Article
Peer-Review Record

Study on the Characteristics of Effective Internal Friction Angles of Silty Clay from the Yellow River Delta and the Inverse Method of CPTu Testing

Appl. Sci. 2023, 13(19), 10724; https://doi.org/10.3390/app131910724
by Huazhong Qi 1,2, Han Wang 3, Chao Yan 4,*, Yuanzhe Zhan 3 and Keliang Qiang 1
Reviewer 1: Anonymous
Reviewer 2:
Reviewer 3: Anonymous
Appl. Sci. 2023, 13(19), 10724; https://doi.org/10.3390/app131910724
Submission received: 14 July 2023 / Revised: 16 September 2023 / Accepted: 17 September 2023 / Published: 27 September 2023
(This article belongs to the Special Issue State of the Art of Rock Mechanics and Geotechnical Engineering)

Round 1

Reviewer 1 Report

The reviewed paper discusses the mechanical properties of silty clay in the Yellow River Delta region. The authors established a method for the inversion of strength parameters using in-situ CPTu testing. This topic is important and interesting for the field of geotechnical engineering. The topic is suitable for the publication in this journal. Some minor revision needs to be addressed before acceptance can be made.

1. Please articulate the novelty and the significance of your paper in the appropriate sections of the manuscript. In particular, where have you improved compared to your previous publications? This is the most important criterion for acceptance.

2. The CPTu tests of  silty clay in the Yellow River Delta can reveal many phenomena and provide the basis for the study of the mechanism of reinforcing effect. However, it should be noted that the experimental laws obtained cannot be directly used in engineering due to the boundary, the specimen state, the way of loading and other factors. The scope of application of this study (including the presented empirical equations) should be written.

3. What ASTM standards or other test procedures are used to obtain basic parameters for silty clay soils? Please provide more information on this.

4. It is recommended that more details of laboratory tests be provided, and typical photos may be added to the text.

5. It is noted that your manuscript needs to be carefully edited by someone with expertise in technical English editing, with particular attention to English grammar, spelling, and sentence structure to make the research objectives and outcomes clear to readers.

1. It is noted that the manuscript needs to be carefully edited by someone with expertise in technical English editing, with particular attention to English grammar, spelling, and sentence structure to make the research objectives and outcomes clear to readers.

Author Response

Dear reviewer:

Thank you for your decision and constructive comments on my manuscript. We have carefully considered the suggestion of the Reviewer and made some changes. We have tried our best to improve and made some changes to the manuscript.

The yellow part has been revised according to your comments. Revision notes, point-to-point, are given as follows:

Comment 1

Please articulate your paper's novelty and significance in the appropriate sections of the manuscript. In particular, where have you improved compared to your previous publications? This is the most essential criterion for acceptance.

Response

We appreciate your observation. We have made the necessary revisions to address this concern and improve the paper's clarity. Based on your suggestions, we have carefully revised the introduction, emphasizing the innovation of this method. The specific modifications are as follows:

Since soil's effective internal friction angle remains relatively consistent for soils with similar mineral composition and particle distribution, this experiment extracted representative soil samples from a silty clay area of a shield tunnel construction site. Through indoor calibration tank tests, it is possible to calibrate the suggested values for the effective internal friction angle suitable for this specific region. This approach offers a more efficient method for obtaining in-situ parameters such as the effective internal friction angle and undrained shear strength during future exploration activities in the same region.

Comment 2

The CPTu tests of silty clay in the Yellow River Delta can reveal many phenomena and provide the basis for studying the reinforcing effect mechanism. However, it should be noted that the experimental laws obtained cannot be directly used in engineering due to the boundary, the specimen state, the way of loading, and other factors. The scope of application of this study (including the presented empirical equations) should be written.

Response

Your insight is well-taken. We have reworked the relevant sections to enhance our arguments' logical flow and coherence. In this regard, we have made careful revisions, providing the conditions under which boundary effects are influential and the methods employed by our experimental setup to eliminate these effects. To mitigate the impact caused by the loading plate, we have excluded the non-steady-state upper section and selected data from the stable penetration interval in the lower portion. Thus, our approach allows us to effectively mitigate the effects of boundary conditions and closely replicate the in-situ conditions during the tests conducted in this study:

In silty clay, when the ratio of the diameter of the soil sample to the diameter of the CPTu probe is greater than 25, the influence of boundary effects can be ignored. The design of this consolidation apparatus considers this factor. The probe diameter is designed to be 16 mm, and the soil sample diameter is 600 mm, resulting in a diameter ratio of 37.5. This effectively eliminates the influence of rigid boundary effects.

Comment 3

What ASTM standards or other test procedures obtain basic parameters for silty clay soils? Please provide more information on this.

Response

We mainly utilized the ASTM D2487-2017 (USCS) plasticity chart for reference. We have supplemented this information in the original text.

Comment 4

It is recommended that more details of laboratory tests be provided, and typical photos may be added to the text.

Response

Thank you for your advice; we have documented the experimental process with photos and integrated them into the article.

Comment 5

It is noted that your manuscript needs to be carefully edited by someone with expertise in technical English editing, with particular attention to English grammar, spelling, and sentence structure to make the research objectives and outcomes clear to readers.

Response

We apologize for the poor language in our manuscript. We have been working on the manuscript for a long time, repeatedly adding and deleting sentences and chapters, clearly resulting in poor readability. We have now researched language and readability and involved English professionals in language correction. We hope for a substantial improvement in traffic and language proficiency.

Author Response File: Author Response.docx

Reviewer 2 Report

The present article presents a study on the characteristics of effective internal friction angle of silty clay in

the Yellow River Delta and the inverse method of CPTu testing. Prior to the second round of revisions, the following major revisions must be addressed:

The abstract requires updating to provide a concise overview of the study, including the context, research question, hypothesis, methodology, key findings, and conclusions. Ideally, it should also contextualize the findings within the broader research area.

The introduction section requires a more detailed discussion leading to the problem statement and scope of the study. Additionally, additional literature must be included to support statements made in the text: Line 36-37 please cite https://doi.org/10.1016/j.trgeo.2022 ; line 115-116 cite: 100781https://doi.org/10.1016/j.jobe.2022.104152 ; line 204 cite https://doi.org/10.1016/j.trgeo.2021.100697

In addition to outlining the research goals, the novelty of the work should be clearly and effectively highlighted in the final paragraph of the introduction.

The methodology must be refined to ensure that it is logical, clear, and replicable by other researchers. If any portion or all of the methodology has been published elsewhere, it must be briefly summarized and cited accordingly.

The text could benefit from more detailed explanations on inversion of undrained shear strength based on CPTu. This would help readers better understand the findings of this study. Also, explain the technical implications of Figs 8=10.

 

Lastly, the conclusion needs to provide all novel and important findings of the study, with the significance of the work stated explicitly.

moderate

Author Response

Dear reviewer:

Thank you for your decision and constructive comments on my manuscript. We have carefully considered the suggestion of the Reviewer and made some changes. We have tried our best to improve and made some changes to the manuscript.

The yellow part has been revised according to your comments. Revision notes, point-to-point, are given as follows:

Comment 1

The abstract requires updating to provide a concise study overview, including the context, research question, hypothesis, methodology, key findings, and conclusions. Ideally, it should also contextualize the results within the broader research area.

Response

We are greatly appreciative of your review. To address this concern and enhance the logical coherence of the paper, we have made necessary revisions. Following your advice, we have meticulously revised the abstract and added completeness to this section. The specific modifications are as follows:

This study focuses on the silty clay of the Yellow River tunnel, conducting laboratory experiments to explore the strength characteristics of typical silty clay in the Yellow River tunnel. The study utilizes CPTu calibration tests to systematically reveal the features of cone tip resistance (qt), side friction resistance (fs), and pore water pressure (u2) of the silty clay. This research provides a theoretical basis for tunnel investigation in the Yellow River region. The study compares the applicability of existing CPTu inversion methods and highlights the NTH method's advantages in evaluating silty clay's effective internal friction angle. Supported by indoor calibration tank tests, the study confirms the reliability of the NTH method in estimating the effective internal friction angle under usually consolidated conditions while identifying its limitations. These research findings offer data support for the in-situ rapid and accurate estimation of design parameters like the internal friction angle and undrained shear strength of shield tunnels in the silty clay area of the Jinan Yellow River tunnel. Moreover, they provide insights for obtaining other crucial in-situ data.

Comment 2

The introduction section requires a more detailed discussion leading to the problem statement and scope of the study. Additionally, additional literature must be included to support statements in the text: Line 36-37, please cite https://doi.org/10.1016/j.trgeo.2022. 100781; line 115-116 cite: https://doi.org/10.1016/j.jobe.2022.104152; line 204 cite https://doi.org/10.1016/j.trgeo.2021.100697.

Response

We have reviewed relevant literature and cited it in the response location

Comment 3

In addition to outlining the research goals, the novelty of the work should be clearly and effectively highlighted in the final paragraph of the introduction.

Response

We appreciate your observation. We have made the necessary revisions to address this concern and improve the paper's clarity. Based on your suggestions, we have carefully revised the introduction

production, emphasizing the innovation of this method. The specific modifications are as follows:

Since soil's effective internal friction angle remains relatively consistent for soils with similar mineral composition and particle distribution, this experiment extracted representative soil samples from a silty clay area of a shield tunnel construction site. Through indoor calibration tank tests, it is possible to calibrate the suggested values for the effective internal friction angle suitable for this specific region. This approach offers a more efficient method for obtaining in-situ parameters such as the effective internal friction angle and undrained shear strength during future exploration activities in the same region.

Comment 4

The methodology must be refined to ensure that it is logical, clear, and replicable by other researchers. If any portion or all of the method has been published elsewhere, it must be briefly summarized and cited accordingly.

Response

Thank you very much for the method proposed by Janbu and Senneset. Sandven, Sandven, and Watn et al. have improved it (cited in the article), but they all used data from on-site in-situ testing. The on-site strata are relatively complex, so a large amount of data is needed for calculation. This article takes representative soil samples from the strata for indoor calibration tank testing, and the experimental purpose is clear; only a small amount of experiments are needed to obtain empirical formulas. This article verifies the applicability of the NTH method in silty clay in the Yellow River Delta region through indoor and static penetration tests.

Comment 5

The text could benefit from more detailed explanations on inversion of undrained shear strength based on CPTu. This would help readers better understand the findings of this study. Also, explain the technical implications of Figs 8=10.

Response

We have changed the content of this section to focus on the inversion method of undrained shear strength in obtaining the cone coefficient Nkt. By comparing the indoor test results with the theoretical solution results, we have verified the reliability of the parameters obtained from the indoor test.

Figure 8 (now Figure 12) mainly shows the results of using the NTH method to calculate silty clay's effective internal friction angle in the Yellow River Delta region (Figure 1). Figure 9 (now Figure 13) mainly shows the consistency between the inversion results obtained through static cone penetration and the indoor triaxial test results. Figure 10 (now Figure 14) shows the consistency between the theoretical calculation of Nkt and the indoor static cone penetration calibration of Nkt.

Comment 6

Lastly, the conclusion needs to provide all novel and important findings of the study, with the significance of the work stated explicitly.

Response

Based on your feedback, we have re-summarized the entire text:

This paper presents a comprehensive study on normally consolidated silty clay from the Yellow River Delta through geotechnical and laboratory CPTu tests. Utilizing results from indoor calibration chamber tests, cone tip resistance (qc) and pore water pressure (u2) were obtained. These values were then used to interpret essential parameters such as effective internal friction angle and the coefficient Nkt for determining undrained shear strength. These interpretations were compared with indoor test results. The research findings are summarized as follows:

  1. A series of indoor tests were conducted on samples of the original state of silty clay from the Yellow River Delta to determine their basic physical and mechanical properties.
  2. The NTH (Normalized Tangent Hyperbolic) method was applied using data obtained during the penetration phase of the indoor calibration chamber test. Analysis indicated that while the NTH method might yield slightly lower effective internal friction angle results for the silty clay, the overall consistency is good. This suggests the reliability of the NTH method for inferring effective internal friction angle for normally consolidated silty clay in the Yellow River Delta. Additionally, this approach avoids the complexity and extensive field testing required to establish patterns and, inversely, model detailed parameters of a specific stratum.
  3. The coefficient Nkt for the silty clay in the Yellow River Delta region was successfully inversely determined. The results show excellent agreement with theoretical values, providing recommended values for Nkt. This information is essential for deriving the undrained shear strength during the inverse process and offers crucial empirical coefficients for on-site geological testing in this region.

Author Response File: Author Response.docx

Reviewer 3 Report

The work presentd here is interesting and suitable for the section. 

The Manuscript needs a through revision of expression and redaction. In general it is hard to understand most of the statements. 

A good description of sample; location map, visual aspect, type of sample, obtaining method will improve the work  

The research work deals in applying the so called inversion method to correlate effective friction angle  obtained  by mini CPTu and  drained triaxial  tests. The results obtained and interpretation of CPTu are interesting.  But  the laboratory test data are not. First of all, the whole study is based only  on one soil sample, most of data are not clear,  interpration is not properly explained.  It is recommended to revise well the triaxial laboratory test results and make some brifing about the procedures used to obtaine or interpret parameters . See manuscript. It is beter to avoid some interpration which are not necesarry for the conclusiones. Ex. Strain Hardening, critical state. 

 

 

 

 

The work is interesting and suitable for the journal and the section. 

The Manuscript needs a thorough revision of expression and redaction to make it easily understandable to the reader. 

Comments are included in the manuscript and to the author. 

 

 

 

Author Response

Dear reviewer:

Thank you for your decision and constructive comments on my manuscript. We have carefully considered the suggestion of the Reviewer and made some changes. We have tried our best to improve and made some changes to the manuscript.

The yellow part has been revised according to your comments. Revision notes, point-to-point, are given as follows:

Comment 1

The Manuscript needs a through revision of expression and redaction. In general it is hard to understand most of the statements. 

Response

We apologize for the poor language in our manuscript. We have been working on the manuscript for a long time, repeatedly adding and deleting sentences and chapters, clearly resulting in poor readability. We have now researched language and readability and involved English professionals in language correction. We hope for a substantial improvement in traffic and language proficiency.

Comment 2

A good description of sample; location map, visual aspect, type of sample, obtaining method will improve the work.

Response

Based on your suggestion, we have added photos of the sampling location and close-up of the sample.

Comment 3

The research work deals in applying the so called inversion method to correlate effective friction angle  obtained  by mini CPTu and  drained triaxial  tests. The results obtained and interpretation of CPTu are interesting.  But  the laboratory test data are not. First of all, the whole study is based only  on one soil sample, most of data are not clear,  interpration is not properly explained.  It is recommended to revise well the triaxial laboratory test results and make some brifing about the procedures used to obtaine or interpret parameters . See manuscript. It is beter to avoid some interpration which are not necesarry for the conclusiones. Ex. Strain Hardening, critical state. 

Response

Based on your suggestion, we have supplemented several sets of triaxial test data for typical silty clay areas, and obtained the range of effective internal friction angles for silty clay, highlighting the universality of the experimental results in this paper.

 

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Accept in current form. Congrats!

moderate

Author Response

Please see the attachment. Thank you!

Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript has been improved based on the previous comments.  

There are only few comments  

Figure 5, of the stress-strian representation of the sample is missed

Figure 6 must say p-q`. 

I still think that the manuscript need some english revisión 

Author Response

Please see the attachment. Thank you!

Author Response File: Author Response.docx

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