Analysis of Surface Settlement Induced by Shield Tunnelling: Grey Relational Analysis and Numerical Simulation Study on Critical Construction Parameters

Round 1

Reviewer 1 Report

The paper investigated the surface settlement in the urban subway construction section of Qingdao Metro Line 6 between Haigang Road Station and Chaoyang Road Station. The authors employed a hybrid numerical approach comprising grey relational analysis and numerical simulations to identify the critical construction parameters and their effects on surface settlement. The study provides valuable insights into how to mitigate surface settlement during shield tunnel construction. The paper is well organized and the research method is rigorous. Here are some suggestions and questions:

1. In Section 2, please provide the arrangement of monitoring points. 

2. In Section 3, please state how the grey relational analysis was employed to assess the relationship among the selected influential factors. 

3. In Section 4, please provide more critical information on simulation methodology, such as the numerical solution approach, the models or the subroutines employed. 

4. In Section 4.2, please elaborate more clearly the cyclic tunnelling process employed in the mode. 

5. Is the term "Solidified parameter", as used in Section 4.2, defined elsewhere? If so, please specify this parameter in the manuscript.

 

It is suggested that the manuscript should be edited by native English speaking experts, which will further improve the quality of the manuscript.

 

 

Author Response

Dear Reviewer,

 

We sincerely appreciate your valuable feedback on our paper. We have carefully considered your suggestions and made corresponding revisions to improve our manuscript. Here is our response to your comments:

 

1. In Section 2, please provide the arrangement of monitoring points.

Regarding the arrangement of monitoring points, we have added a layout plan of monitoring sites at the Haigang Road Station in Section 2 (now Figure 2 in the revised manuscript).

 

2. In Section 3, please state how the grey relational analysis was employed to assess the relationship among the selected influential factors.

At the beginning of Section 3, we have added a brief description of the calculation steps to explain how this method was employed to assess the relationship among the selected influential factors.

 

3. In Section 4, please provide more critical information on simulation methodology, such as the numerical solution approach, the models or the subroutines employed.

In Section 4, we have restructured the content of simulation methodology. We have combined the information regarding simulation assumptions, global parameter settings, and simulation processes in the Section 4.1 “Simulation setup”. In addition, we have introduced Flac3D in the first paragraph of Section 4 to provide more details about the simulation tool.

 

4. In Section 4.2, please elaborate more clearly the cyclic tunnelling process employed in the mode.

In Section 4.2, we have elaborated the cyclic tunnelling process in more detail to enhance its clarity and comprehensibility.

 

5. Is the term "Solidified parameter", as used in Section 4.2, defined elsewhere? If so, please specify this parameter in the manuscript.

Regarding the term "Solidified parameter," we have made adjustments to use "Grouting layer (Post-Solidification)" throughout the manuscript to refer to parameters after the grouting layer has solidified.

 

We genuinely thank you for your review and valuable suggestions. These revisions will contribute to enhancing the quality and comprehensibility of our paper. If you have any further suggestions or requests, we would be more than willing to further improve our work. Once again, thank you for your time and professional insights.

 

Sincerely,

All Authors

Author Response File: Author Response.pdf

Reviewer 2 Report

The followings should be addressed for further consideration:

-        Literature review is poor and it needs to include latest state of the art papers on the topic. Thus, please discuss the followings:

Wang, F., Du, X. and Li, P., 2023. Predictions of ground surface settlement for shield tunnels in sandy cobble stratum based on stochastic medium theory and empirical formulas. Underground Space, 11, pp.189-203.

Moghtader, T., Sharafati, A., Naderpour, H. and Gharouni Nik, M., 2023. Estimating Maximum Surface Settlement Caused by EPB Shield Tunneling Utilizing an Intelligent Approach. Buildings, 13(4), p.1051.

Alzabeebee, S. and Keawsawasvong, S., 2023. Numerical assessment of microtunnelling induced pavement settlement. Geotechnical and Geological Engineering, 41(3), pp.2173-2184.

-        Novelty of the paper should be stressed in the introduction. It is not clear what gap in knowledge this paper tries to address.

-        It is not clear why the authors used very simple model (i.e., the Mohr Columb model) to simulate a tunnelling problem. This problem needs a model that considers the try behavior of the soil such as volume change, stiffness sensitivity to stress level and irrecoverable deformation. I think this is a fundamental flaw in the methodology.

-        It is not clear how the authors derived the parameters listed in Table 1. More details are needed.

-        Also, you need to state the type of stiffness modules used in the analysis. Is it secant or tangential.

-        How did you ensure that the mesh reported in Figure 3 is appropriate.

-        Why you used the linear elastic model to simulate the tunnelling and shield zone. Details are needed.

-        Self-citation should be reduced.

 

 

 

Author Response

Dear Reviewer,

 

We sincerely appreciate your thorough review and valuable feedback on our manuscript. Your insights have been instrumental in enhancing the quality of our work. Here is our response to each of your comments and suggestions:

 

1. Literature review is poor and it needs to include latest state of the art papers on the topic. Thus, please discuss the followings:

 

Wang, F., Du, X. and Li, P., 2023. Predictions of ground surface settlement for shield tunnels in sandy cobble stratum based on stochastic medium theory and empirical formulas. Underground Space, 11, pp.189-203.

 

Moghtader, T., Sharafati, A., Naderpour, H. and Gharouni Nik, M., 2023. Estimating Maximum Surface Settlement Caused by EPB Shield Tunneling Utilizing an Intelligent Approach. Buildings, 13(4), p.1051.

 

Alzabeebee, S. and Keawsawasvong, S., 2023. Numerical assessment of microtunnelling induced pavement settlement. Geotechnical and Geological Engineering, 41(3), pp.2173-2184.

We are grateful for your insightful comment about the need to enhance our literature review with the latest state-of-the-art papers in the field. We have diligently reviewed the papers you mentioned, including Wang et al., Moghtader et al., and Alzabeebee et al. These papers have been incorporated into our revised literature review to provide a more comprehensive overview of recent development of study on ground surface settlement induced by shield tunneling.

 

2. Novelty of the paper should be stressed in the introduction. It is not clear what gap in knowledge this paper tries to address.

We have revised the introduction section to highlight the novelty of our study and the knowledge gap we tried to address. We emphasize how our research uniquely combines grey relational analysis and numerical simulation to provide a more accurate analysis of surface settlement issues and practical engineering recommendations compared to existing studies.

 

3. It is not clear why the authors used very simple model (i.e., the Mohr Columb model) to simulate a tunnelling problem. This problem needs a model that considers the try behavior of the soil such as volume change, stiffness sensitivity to stress level and irrecoverable deformation. I think this is a fundamental flaw in the methodology.

We appreciate your suggestion regarding the choice of the Mohr-Coulomb model. Due to limitations in experimental data, we could not access additional parameters for more complex models. We have acknowledged this limitation in the discussion and plan to address it in future research by supplementing experimental data and develop the constitutive model to capture variations of material deformation behaviors more comprehensively.

 

4. It is not clear how the authors derived the parameters listed in Table 1. More details are needed.

To provide more details on the parameters listed in Table 1 (now Table 2 in the revised manuscript), we have added supplementary information in the section 2. The parameters listed in the Table were obtained from the "Geotechnical Investigation Report of Qingdao Metro Line 6 Phase I Project, Haigang Road Station - Chaoyang Road Station" provided by the Qingdao Survey and Mapping Research Institute.

 

5. Also, you need to state the type of stiffness modules used in the analysis. Is it secant or tangential

We have added the note information below the table to specify that the elastic modulus used in this paper represents the tangential stiffness modulus.

 

6. How did you ensure that the mesh reported in Figure 3 is appropriate.

To ensure the appropriateness of the mesh reported in Figure 3, we employed two main approaches. First, we conducted simulations with different grid densities and selected the scheme of mesh division where the results did not exhibit significant further refinement. Second, we compared simulation results with monitoring data from the actual construction site, demonstrating a close agreement between simulated and observed settlements, which provides confidence in the accuracy of our mesh and simulation approach. Additional details on mesh density verification are now provided in Section 4.2, and simulation result validation is supplemented in the newly added Section 4.4.

 

7. Why you used the linear elastic model to simulate the tunnelling and shield zone. Details are needed.

Given that our analysis focuses on short-term material responses of the shield shell and lining, where permanent plastic deformations can be negligible, and there is no progressive failure or nonlinear bending behavior simulated, we chose the linear elastic model to simplify calculations and improve efficiency. We have now included this information in Section 4.2.

 

8. Self-citation should be reduced.

We acknowledge that while self-citation can be necessary to provide context and background for our research, it should be used judiciously and only when relevant. We have carefully reviewed our paper and made efforts to reduce self-citation wherever possible without compromising the clarity and completeness of our references.

 

We are committed to addressing these concerns comprehensively in our revised manuscript to meet the high standards of the journal. Your guidance is invaluable, and we genuinely appreciate your time and effort in reviewing our work. If you have any additional comments or questions, please do not hesitate to reach out to us. We look forward to the opportunity to improve our manuscript based on your feedback..

 

Sincerely,

All Authors

Author Response File: Author Response.pdf

Reviewer 3 Report

·        The authors must include some relevant cases/references in the recent past where TBM excavation caused surface settlements and damage to structures.

 

·        Provide details about the flexibility of TBM operational parameters.

 

·        Present relevant research in this specific area and demonstrate the novelty of this study.

 

·        The modeling results show that the model dimensions are insufficient.

 

·        What is the status of settlements ahead of the TBM?

 

·        Discuss model validation.

 

·        The scope of the study is extensive, and the parametric results are discussed without a comprehensive consideration of existing literature.

 

·        Please make your conclusion more concise.

moderate editing

Author Response

Dear Reviewer,

 

We would like to extend our heartfelt gratitude for your comprehensive review and constructive suggestions on our manuscript. Your feedback has been instrumental in enhancing the quality and clarity of our research. Below, we provide a summary of the actions we have taken in response to your valuable recommendations:

 

1. The authors must include some relevant cases/references in the recent past where TBM excavation caused surface settlements and damage to structures.

In the introduction section, we have included more relevant cases from recent past experiences where TBM excavation caused surface settlements and damage to structures.

 

2. Provide details about the flexibility of TBM operational parameters.

In Section 2, We added a new table (now Table 1 in the revised manuscript) to list the TBM operational parameters to provide a more clear understanding of the flexibility and significance of these parameters in the context of our study.

 

3. Present relevant research in this specific area and demonstrate the novelty of this study.

We have revised the literature review section and refined it to highlight the novelty of our study. We emphasize how our research uniquely combines grey relational analysis and numerical simulation to provide a more accurate analysis of surface settlement issues and practical engineering recommendations compared to the existing studies.

 

4. The modeling results show that the model dimensions are insufficient.

Regarding the modeling results and model dimensions, we appreciate your understanding of the difficulties in selecting model sizes. While we acknowledge the limitations imposed by computational resources and other factors, we have endeavored to select a representative section for numerical simulation. In the future, we aim to expand model dimensions to capture more complex underground engineering scenarios.

 

5. What is the status of settlements ahead of the TBM?

Regarding settlements ahead of the TBM, we would like to clarify our research focus. Our primary emphasis is the analysis of surface settlements induced by TBM excavation after the shield machine passed through a particular area. The settlement patterns observed in front of the TBM are generally similar to those observed behind it. Typically, we observed a gradual increase in settlement as the TBM advances, and then converged to stability after a small retraction. Notably, the maximum surface settlement tends to occur behind the TBM. Consequently, our study primarily centers on the analysis of post-TBM construction surface settlements. We hope this clarifies our research scope and approach.

 

6. Discuss model validation.

We have added a model validation section to provide a more comprehensive explanation of the methods and processes used to validate our numerical model. We also included additional monitoring points for assessing simulation accuracy.

 

7. The scope of the study is extensive, and the parametric results are discussed without a comprehensive consideration of existing literature.

We have improved the results analysis section and included discussion of relevant existing literature, providing a more comprehensive analysis of our parametric results.

 

8. Please make your conclusion more concise.

We have refined the conclusion section, removed redundancies, and relocated the construction recommendations to the discussion section.

 

Once again, we deeply appreciate your meticulous review and constructive feedback, which have undoubtedly strengthened the rigor and comprehensiveness of our work. Should you have any further comments or recommendations, please do not hesitate to share them with us. Your contributions are invaluable to our research progress.

 

Sincerely,

All Authors

Author Response File: Author Response.pdf

Reviewer 4 Report

The article uses gray correlation analysis and numerical simulation methods to extract the key factors of surface subsidence and analyze the factors of surface subsidence. Although the method used in the article is not novel and the innovation points are not good, the overall content is rich and the research background is appropriate. The project is practical and significant, and the article is well written. It is proposed to accept the revised submission, but some parts require correction and explanation, as follows:

1. In the second chapter, in addition to the text description, it is also suggested to provide a schematic diagram of geographical information in addition to the geological profile, so that readers can understand the project overview more intuitively (recommended to adopt).

2. In Table 1 on line 126, pay attention to the unit, such as the density unit, and also pay attention to the numerical conversion between units. For example, plain fill soil should be 1650Kg/m-3, or 16500N/m-

3. Unify the graphic format of Figure 2. In addition, will the relational coefficients in the graphic exceed 1? Please ensure the accuracy of the data.

Author Response

Dear Reviewer,

 

We sincerely appreciate your thoughtful feedback and recommendations on our manuscript. We have carefully considered your suggestions and made the necessary improvements to address each of your concerns. Here are our responses:

 

1. In the second chapter, in addition to the text description, it is also suggested to provide a schematic diagram of geographical information in addition to the geological profile, so that readers can understand the project overview more intuitively (recommended to adopt).

In the second chapter, We have included additional schematic diagrams of geographical information (now Figure 2 and Figure 3 in the revised manuscript) to provide readers with a more intuitive overview of the project area, including the layout of monitoring points and aerial views near the Haigang Road station. We believe this addition will greatly enhance the reader's understanding of the project.

 

2. In Table 1 on line 126, pay attention to the unit, such as the density unit, and also pay attention to the numerical conversion between units. For example, plain fill soil should be 1650Kg/m^-3, or 16500N/m^-3.

Thank you for pointing out the unit error. We have revised the unit and ensured consistency throughout the table (now Table 2 in the revised manuscript). Specifically, plain fill soil density is now correctly represented as 1650 kg/m³.

 

3. Unify the graphic format of Figure 2. In addition, will the relational coefficients in the graphic exceed 1? Please ensure the accuracy of the data.

We have standardized the graphic format of the figure (now Figure 4 in the revised manuscript). Regarding the relational coefficients, we acknowledge that the perspective view in the 3D graph might create an impression that some coefficients exceed 1. To address this potential misunderstanding, we have transformed the image into a plan view, eliminating any visual appearance of coefficients exceeding 1.

 

We believe that these revisions have improved the quality and clarity of the manuscript, aligning it more closely with your recommendations. We are grateful for your thorough review and constructive suggestions, which have contributed to enhancing the overall quality of our work. If you have any further comments or suggestions, please feel free to share them. Your expertise and insights are highly valuable to us.

 

Sincerely,

All Authors

Author Response File: Author Response.pdf

Reviewer 5 Report

The manuscript (Manuscript ID: sustainability-2607320) is entitled: Analysis of Surface Settlement Induced by Shield Tunnelling: Grey Relational Analysis and Numerical Simulation Study on Critical Construction Parameters.

This manuscript focused on investigating the surface settlement induced by shield tunnelling during the construction of Qingdao Metro Line 6 between Haigang Road Station and Chaoyang Road Station. Firstly, the settlement data from the left line of the shield tunnel were evaluated by grey relational analysis method. The relational coefficients were calculated to assess the correlation degrees of each influential parameter. Subsequently, the four critical influential parameters with the highest relational degrees were chosen to investigate their effects on surface settlement through numerical simulations under different scenarios. The results show that the four parameters with the highest relational degrees were: thrust, grouting pressure, earth pressure, and strata elastic modulus. The grey relational analysis method and numerical methods FLAC3D were used to prove the accuracy of the calculations. This is a good quality manuscript and this manuscript aligns perfectly with the journal's scope.

However, there are small issues with this manuscript that require editing and improvement:

1, In Figures 2, according to the reviewer, the semitransparent plane should have a relational coefficient value of 0.7, which will ensure the correlation threshold between the influential parameters and the surface settlement;

2, There should be a chart comparing the influence of parameters on surface settlement during tunnel construction through the values of the coefficient relational;

3, The study did not mention the influence of groundwater. Groundwater is an important parameter that greatly affects surface settlement during tunnel construction, particularly in urban areas with shallow tunnels;

 

4, When the authors create the tunnel model in FLAC3D software with soil or rock surrounding it, it's better to use the hardening soil model instead of the Mohr-Coulomb model.

Author Response

Dear Reviewer,

 

We sincerely appreciate your insightful feedback and suggestions on our manuscript. We have taken your comments into careful consideration and implemented the following revisions and improvements:

 

1. In Figures 2, according to the reviewer, the semitransparent plane should have a relational coefficient value of 0.7, which will ensure the correlation threshold between the influential parameters and the surface settlement;

We have adjusted the threshold value of the semitransparent plane to 0.7 in the figure (now Figure 4 in the revised manuscript). This modification enhances the visibility of the correlation between influential parameters and surface settlement, providing a clearer representation of the data.

 

2. There should be a chart comparing the influence of parameters on surface settlement during tunnel construction through the values of the coefficient relational;

We have included a chart (now Table 4 in the revised manuscript) that compares the influence of parameters on surface settlement during tunnel construction based on the relational coefficient values. This chart will enable readers to better understand the relative impact of different factors on surface settlement.

 

3. The study did not mention the influence of groundwater. Groundwater is an important parameter that greatly affects surface settlement during tunnel construction, particularly in urban areas with shallow tunnels;

We acknowledge the importance of groundwater as a significant parameter affecting surface settlement during tunnel construction, especially in urban areas with shallow tunnels. In response, we have added a discussion on groundwater in the section 5. Additionally, we plan to incorporate groundwater factor into our future analyses and simulations to provide a more comprehensive understanding of the phenomenon.

 

4. When the authors create the tunnel model in FLAC3D software with soil or rock surrounding it, it's better to use the hardening soil model instead of the Mohr-Coulomb model.

We appreciate your suggestion to use the hardening soil model instead of the Mohr-Coulomb model when creating the tunnel model in FLAC3D software. We acknowledge and discuss this limitation of our work in section 5. We plan to address it in future study by supplementing experimental data, utilizing more advanced constitutive models, or developing new models to comprehensively reflect variations of material deformation behaviors.

 

We believe these modifications and future research plans will enhance the quality and depth of our work. Your feedback has been instrumental in improving our manuscript, and we sincerely thank you for your thoughtful review. If you have any additional comments or suggestions, please do not hesitate to share them with us.

 

Sincerely,

All Authors

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The comments have been addressed and the paper could be accepted for publication.

Author Response

Dear Reviewer,

 

We are excited about the opportunity to have our paper published and look forward to contributing to the academic community.

 

1. The comments have been addressed and the paper could be accepted for publication.

Thank you very much for your positive feedback and for acknowledging that the comments have been effectively addressed. We are delighted to hear that our revisions have met your expectations, and we greatly appreciate your time and expertise in reviewing our manuscript.

 

Please let us know if there are any additional steps or information required to proceed with the publication process. Once again, thank you for your valuable insights and support.

 

Sincerely,

All Authors

Author Response File: Author Response.pdf

Reviewer 3 Report

Concise the conclusion

Minor 

Author Response

Dear Reviewer,

 

We greatly appreciate your constructive feedback during the second round of review. Your suggestion to "Concise the conclusion" has been diligently implemented.

 

1. Concise the conclusion.

In response to your advice, we have conducted additional refinement and streamlining of the conclusions section, building upon the modifications implemented in the first review. Furthermore, we conducted a comprehensive review of the entire manuscript to ensure the conclusions within each section are concise while maintaining clarity and comprehensiveness. We believe that these revisions have improved the overall readability and impact of our manuscript's conclusion while maintaining the necessary depth of analysis.

 

Thank you for your continued guidance, which has contributed significantly to enhancing the quality of our work.

 

Sincerely,

All Authors

Author Response File: Author Response.pdf