Laws and Numerical Analysis of Surface Deformation Caused by Excavation of Large Diameter Slurry Shield in Upper-Soft and Lower-Hard Composite Stratum

Round 1

Reviewer 1 Report

Point 1: From lines 6 through 9, kindly remove this part and strictly follow how to abbreviate authors' names following their e-mail addresses.

Point 2: In the abstract, kindly remove the numerical values listing the study's results. Provide also a conclusion.

Point 3: In the abstract, line 15, kindly replace the term 'soil' with a more appropriate one as tunnel construction does not only involve the removal of soil materials.

Point 4: In the abstract, kindly provide specific details on the field monitoring (i.e., instrument type) and finite element simulation (i.e., 2D or 3D and simulation tool used).

Point 5: In the abstract, line 24, the last phrase (should be …) is not appropriate in the abstract.

Point 6: In line 49, kindly put the reference number after Peck.

Point 7: In line 52, kindly define the variables stated.

Point 8: In line 55, kindly follow the correct format for reference citation.

Point 9: In line 64, Kindly replace 'researches' with 'studies' because 'researches' is not the correct word. Also, cite some relevant papers.

Point 10: How is the paper different from other published works? What limitations of similar studies? These should be explicitly stated/included in the introduction.

Point 11: Kindly also provide a concise discussion on the in-situ monitoring scheme in Section 2.

Point 12: Figure 1a needs more details, such as geometric dimensions. The legend for Figure 1b is not legible. What station or section along the tunnel length the soil profile is represented by the left figure of Figure 1c? How are the remaining figures relevant to the study? Kindly provide more visually appealing schematics with concise descriptions in the main text.

Point 13: In line 94, what do the authors mean by statistical law analysis? This section does not provide any law analysis with a comprehensive statistical approach to surface deformation. Kindly clarify this concern. If not, consider changing the header title with an appropriate one.

Point 14: Is this study's term 'lateral settlement' correct? Kindly use the appropriate term (i.e., transverse).

Point 15: Where are these entrance and exit sections in Figure 1b? Kindly mark them legibly. Are the monitoring points or sections installed on the walls or base of the excavated tunnel or ground surface? Again, kindly provide visually appealing schematics with concise descriptions in the main text. Figures 1c-d do not provide good visuals of how and where the monitoring points are installed.

Point 16: In figure 2, kindly remove the inset figure. This inset figure can confuse the readers as it does not help explain the temporal evolution of surface displacement as shield tunneling progresses.

Point 17: Kindly check the sub-section header title of 3.2.3 and 3.2.4.

Point 18: Where are these monitoring sections DBC located?

Point 19: In figure 3, labels are not legible. Make sure that all labels of all figures are legible.

Point 20: How do these study's assumptions affect the results? Kindly provide a section of the study's limitations due to these assumptions. A concise discussion must be provided.

Point 21: Which part of the tunnel in Figure 1b are the authors trying to simulate? The authors mentioned that the soil condition is complicated, and now the authors are simulating a uniform soil medium. Yes, the authors have some assumptions but do not try to have conflicting thoughts in different sections of the paper. How did the authors consider the interface characteristics (i.e., interaction) between the structure and the soil? How did the authors arrive at the final numerical model dimensions and the final mesh used for the simulation? Did the authors perform a preliminary simulation series?

Point 22: No discussion is provided about how the sensitivity analysis/parametric study was performed.

Point 23: In lines 325 through 329, this sentence is confusing. The sentence needs to be improved grammatically.

Pont 24: Kindly replace the title of Section 5 with Conclusion instead of Discussion.

Pont 25: Kindly follow the correct format in listing references.

Author Response

Dear reviewers:

We are very grateful to the reviewers for your comments on the manuscript, which enables us to further improve the quality and format of the paper. Each suggested revision and comment, brought forward by the reviewers were carefully considered and corrected.

The following is a response to the revised content of the manuscript based on the comments of the reviewers . The font with a green background indicates the revision of the manuscript based on the comments of the reviewers. The gray background font indicates that the content in the original manuscript is deleted. The yellow background font indicates the content added in the original manuscript. Should you have any questions, please contact us without hesitate.

Thanks again to all reviewers for your hard work and patience.

1. Comments: From lines 6 through 9, kindly remove this part and strictly follow how to abbreviate authors' names following their e-mail addresses.
2. Response: The contents of lines 6 to 9 have been deleted, and the author information has been checked and corrected.

2. Comments: In the abstract, kindly remove the numerical values listing the study's results. Provide also a conclusion.
3. Response: According to your suggestion, we deleted the value of the study's results and gave a brief overview of the relevant conclusions.

The electronic level is used to monitor the surface settlement, and the field monitoring data are obtained, the surface settlement duration curve at the axis of the shield tunnel during the construction period can be divided into four stages: pre-deformation, shield passing, shield tail exit and shield moving away, of which the surface settlement accounts for the largest proportion during the shield passing.

3. Comments: In the abstract, line 15, kindly replace the term 'soil' with a more appropriate one as tunnel construction does not only involve the removal of soil materials.
4. Response: According to your suggestion, we revised 'soils' to' rocks and soils', which further increased the rigor of the paper.

4. Comments: In the abstract, kindly provide specific details on the field monitoring (i.e., instrument type) and finite element simulation (i.e., 2D or 3D and simulation tool used).
5. Response: According to your suggestion, we further describe the details of field monitoring and numerical simulation in the summary.

Due to the large cross-section design of large-diameter shield tunnels, most of the rocks and soils it crosses are composite strata with upper soft and lower hard. In order to reduce the construction cost of shield working shafts, large-diameter shield launching is usually buried at a shallow depth. Based on the typical large-diameter slurry shield tunnel, the following research results are obtained according to field monitoring and PLAXIS 3D finite element simulation.

In order to ensure the accuracy of the numerical simulation results, the linear shrinkage of the shield needs to be considered in the modeling

5. Comments: In the abstract, line 24, the last phrase (should be …) is not appropriate in the abstract.
6. Response: According to your suggestion, we revised the contents of line 24 of the paper, which further increased the rationality of the words used in the paper.

In order to ensure the accuracy of the numerical simulation results, the linear shrinkage of the shield needs to be considered in the modeling

6. Comments: In line 49, kindly put the reference number after Peck.
7. Response: According to your suggestion, the reference number position has been revised, which is very helpful to increase the readability of the paper.
8. Comments: In line 52, kindly define the variables stated.
9. Response: According to your suggestion, the variables in the text have been explained.

V_loss (Formation loss per unit length of tunnel) and i (Width coefficient of settling trough)

8. Comments: In line 55, kindly follow the correct format for reference citation.
9. Response: According to your suggestion, the numbering position of the references has been revised, which is very helpful to increase the readability of the paper.

9. Comments: In line 64, Kindly replace 'researches' with 'studies' because 'researches' is not the correct word. Also, cite some relevant papers.
10. Response: According to your suggestion, we have changed 'researches' to' studies', which is very helpful to increase the accuracy of the paper. At the same time, we also cited relevant references to further increase the scientificity of the paper.

10. Comments: How is the paper different from other published works? What limitations of similar studies? These should be explicitly stated/included in the introduction.
11. Response: According to your suggestion, we have explained the difference between this research and other papers.

The above research has laid a good theoretical and practical foundation for this paper, but few studies involve large-diameter slurry shield tunnels. In recent years, with the continuous expansion of the practice of large-diameter shield tunneling, it is urgent to study the laws of environmental effects caused by large-diameter shield tunneling. Due to the large cross-section design of large-diameter shield tunnels, most of the soils it crosses are composite strata with upper soft and lower hard, and in order to reduce the construction cost of shield working shafts, shield tunnels are usually designed to start with shallow overburden. Therefore, this paper is based on the engineering practice of typical large-diameter slurry shield tunneling in No.01 section of Hangzhou Tianmushan Road to Huancheng North Road upgrade project. According to the field monitoring data, the ground settlement caused by large-diameter slurry shield tunnel excavation is divided into four stages, and the proportion of tunnel settlement in each stage is summarized. Through numerical simulation, the influence of linear shrinkage of shield on the rationality of numerical simulation modeling is analyzed, and the influence of key construction parameters of large-diameter slurry shield on surface settlement deformation is comprehensively analyzed. The research results can provide reference for the design and construction of large-diameter slurry shield.

11. Comments: Kindly also provide a concise discussion on the in-situ monitoring scheme in Section 2.
12. Response: According to your suggestion, we further explained the on-site monitoring scheme, which further increased the logic of the article.

The on-site monitoring scheme is determined according to (technical code for monitoring of Urban Rail Transit Engineering) (GB50911-2013). The layout plan of the measuring points is as follows: with the 100m range of the entrance and exit section, a surface settlement monitoring section is laid out at intervals of 10m; outside the 100m range of the entrance and exit section, a surface settlement monitoring section is laid out at intervals of 30m. The monitoring range is distributed within 35m on both sides of the shield tunnel, and the monitoring frequency is 12 hours/time. Figs. 1 (c)-(d) show the layout plan and site layout of ground settlement monitoring points. From the shield launching shaft to the shield receiving shaft, the surface settlement monitoring section is numbered DBC-X (X is the monitoring section number).

12. Comments: Figure 1a needs more details, such as geometric dimensions. The legend for Figure 1b is not legible. What station or section along the tunnel length the soil profile is represented by the left figure of Figure 1c? How are the remaining figures relevant to the study? Kindly provide more visually appealing schematics with concise descriptions in the main text.
13. Response: According to your suggestion, we have replaced Figure 1 (a), which contains more track design information; We have made clearer Figure 1 (b) to facilitate readers to read relevant information; Figure 1 (c) shows the soil profile information around the shield launching shaft, which has been explained in the figure.
14. Comments: In line 94, what do the authors mean by statistical law analysis? This section does not provide any law analysis with a comprehensive statistical approach to surface deformation. Kindly clarify this concern. If not, consider changing the header title with an appropriate one.
15. Response: According to your suggestion, we have changed the title of Section 3 to 'monitoring and analysis of surface deformation of large diameter shield tunnel', which is very helpful to improve the readability of the article.

Monitoring and analysis of surface deformation of large diameter shield tunnel

14. Comments: this study's term 'lateral settlement' correct? Kindly use the appropriate term (i.e., transverse).
15. Response: According to your suggestion, we have revised 'lateral settlement' to 'reverse'.

15. Comments: Where are these entrance and exit sections in Figure 1b? Kindly mark them legibly. Are the monitoring points or sections installed on the walls or base of the excavated tunnel or ground surface? Again, kindly provide visually appealing schematics with concise descriptions in the main text. Figures 1c-d do not provide good visuals of how and where the monitoring points are installed.
16. Response: According to your suggestion, we have re marked the positions of the shield launching shaft and receiving shaft; The monitoring points in Fig. 1 are surface settlement monitoring points, which are located on the road surface; According to your suggestion, we have further explained the location of monitoring points in Figure 1 (b) ~ (d).

16. Comments: In figure 2, kindly remove the inset figure. This inset figure can confuse the readers as it does not help explain the temporal evolution of surface displacement as shield tunneling progresses.
17. Response: According to your suggestion, we have deleted Figure 2.

17. Comments: Kindly check the sub-section header title of 3.2.3 and 3.2.4.
18. Response: According to your suggestion, we have checked and corrected the titles of sub-sections 3.2.3 and 3.2.4.

18. Comments: Where are these monitoring sections DBC located?
19. Response: We have explained the location of DBC in the paper. From the shield launching shaft to the shield receiving shaft, the surface settlement monitoring section is numbered DBC-X (X is the monitoring section number).

From the shield launching shaft to the shield receiving shaft, the surface settlement monitoring section is numbered DBC-X (X is the monitoring section number).

19. Comments: In figure 3, labels are not legible. Make sure that all labels of all figures are legible.
20. Response: According to your suggestion, we re adjusted the size and position of the labels in Figure 3, which increased the readability of the article.

20. Comments: How do these study's assumptions affect the results? Kindly provide a section of the study's limitations due to these assumptions. A concise discussion must be provided.
21. Response: According to your suggestions, the limitations of numerical simulation assumptions are explained, which can better explain the differences between numerical simulation results and field monitoring.

From the shield launching shaft to the shield receiving shaft, the surface settlement monitoring section is numbered DBC-X (X is the monitoring section number).

21. Comments: Which part of the tunnel in Figure 1b are the authors trying to simulate? The authors mentioned that the soil condition is complicated, and now the authors are simulating a uniform soil medium. Yes, the authors have some assumptions but do not try to have conflicting thoughts in different sections of the paper. How did the authors consider the interface characteristics (i.e., interaction) between the structure and the soil? How did the authors arrive at the final numerical model dimensions and the final mesh used for the simulation? Did the authors perform a preliminary simulation series?
22. Response:

It can be seen from Fig. 6 that the range of numerical simulation starts from 28m after the shield launching shaft and ends at 62m.

The interaction between soil and structure is simulated by the interface element in the finite element software.

After several trial calculations during the modeling process, it is finally determined that the grid size within the tunnel excavation range is 0.2m, the grid size within 5m outside the excavation range gradually changes from 0.2m to 1m, and the grid size of other parts is 1m.

22. Comments: No discussion is provided about how the sensitivity analysis/parametric study was performed.
23. Response: Through a large number of trial calculations, the paper determines the boundary data value of the key construction parameters of the shield in the numerical simulation. In order to avoid the tedious description in the paper, no relevant discussion is made in the paper.

23. Comments: In lines 325 through 329, this sentence is confusing. The sentence needs to be improved grammatically.
24. Response: According to your suggestions, we checked and revised the corresponding contents of the manuscript.

Some scholars believe that this is because it is difficult to consider the reaction force of the soil in front of and around the excavation face to the shield machine during the simulation of tunnel excavation, resulting in errors in the simulation results, which also reflects some defects in the numerical simulation at the present stage [25].

24. Comments: Kindly replace the title of Section 5 with Conclusion instead of Discussion.
25. Response: According to your suggestion, we have changed the title of section 5 from 'discussion' to 'conclusion'.

25. Comments: Kindly follow the correct format in listing referenceds.
26. Response: According to your suggestion, we corrected the format of references according to the paper submission guide.

Author Response File: Author Response.docx

Reviewer 2 Report

Dear Authors, the article is of scientific value, but it can be improved. Here are my comments:

1. Line 64 - " few researches involve large-diameter slurry shield tunnel". Please explain exactly what the authors wrote on this topic, and what your research novelty will be.

2. Fig. 15 - please explain why the line trend of grouting pressure 300kPa is different than other lines

3.Fig. 16 - please explain why the linear shrinkage: 0% has different trend than other linear shrinkages. Why there are two lines with the same value 0%, and different line trends.

4. It seems that paper is a good practical implementation in construction. However, please indicate in the publication what distinguishes this work from others.

5. Chapter 5 looks more like conclusions than discussions.

Author Response

General Comments: the article is of scientific value, but it can be improved. Here are my comments:

Response： Thank you for your valuable suggestions, which are of great help to improving the rigor and scientific nature of the manuscript. The following is our response to your comments.

1. Comments: " few researches involve large-diameter slurry shield tunnel". Please explain exactly what the authors wrote on this topic, and what your research novelty will be.
2. Response: According to your suggestion, we have added the novelty of this study and the difference between this paper and other papers in the introduction.

The above research has laid a good theoretical and practical foundation for this paper, but few studies involve large-diameter slurry shield tunnels. In recent years, with the continuous expansion of the practice of large-diameter shield tunneling, it is urgent to study the laws of environmental effects caused by large-diameter shield tunneling. Due to the large cross-section design of large-diameter shield tunnels, most of the soils it crosses are composite strata with upper soft and lower hard, and in order to reduce the construction cost of shield working shafts, shield tunnels are usually designed to start with shallow overburden. Therefore, this paper is based on the engineering practice of typical large-diameter slurry shield tunneling in No.01 section of Hangzhou Tianmushan Road to Huancheng North Road upgrade project. According to the field monitoring data, the ground settlement caused by large-diameter slurry shield tunnel excavation is divided into four stages, and the proportion of tunnel settlement in each stage is summarized. Through numerical simulation, the influence of linear shrinkage of shield on the rationality of numerical simulation modeling is analyzed, and the influence of key construction parameters of large-diameter slurry shield on surface settlement deformation is comprehensively analyzed. The research results can provide reference for the design and construction of large-diameter slurry shield.

2. Comments: Fig. 15 - please explain why the line trend of grouting pressure 300kPa is different than other lines.
3. Response: With the increasing grouting pressure, the ground surface gradually changes from settlement to uplift, which changes the trend of the curve.

3. Comments: Fig. 16 - please explain why the linear shrinkage: 0% has different trend than other linear shrinkages. Why there are two lines with the same value 0%, and different line trends. According to your question, we checked and corrected the error in the legend in Figure 16.
4. Response: According to your doubts, we have added an explanation for the difference between the trend line with a linear contraction rate of 0% and other curves in the paper.

The influence of linear shrinkage rate on the longitudinal deformation of ground surface is shown in Fig. 16. It can be seen from the figure that the longitudinal settlement and deformation of the surface increases with the increase of the linear shrinkage rate, and the increase value is more obvious. The linear shrinkage rate of the body must be paid attention to when designing the shield machine. Synchronous grouting and secondary grouting should be carried out in time to reduce the influence of construction gaps caused by linear shrinkage rate on surface settlement. When the linear shrinkage rate is 0%, the friction between the shield machine and the surrounding soil increases, causing the ground surface to uplift. Therefore, in order to ensure the accuracy of the numerical simulation results, the linear shrinkage of the shield from the cutter head to the shield tail should be considered.

4. Comments: It seems that paper is a good practical implementation in construction. However, please indicate in the publication what distinguishes this work from others.
5. Response: According to your suggestion, we have explained the difference between this research and other papers.

The above research has laid a good theoretical and practical foundation for this paper, but few studies involve large-diameter slurry shield tunnels. In recent years, with the continuous expansion of the practice of large-diameter shield tunneling, it is urgent to study the laws of environmental effects caused by large-diameter shield tunneling. Due to the large cross-section design of large-diameter shield tunnels, most of the soils it crosses are composite strata with upper soft and lower hard, and in order to reduce the construction cost of shield working shafts, shield tunnels are usually designed to start with shallow overburden. Therefore, this paper is based on the engineering practice of typical large-diameter slurry shield tunneling in No.01 section of Hangzhou Tianmushan Road to Huancheng North Road upgrade project. According to the field monitoring data, the ground settlement caused by large-diameter slurry shield tunnel excavation is divided into four stages, and the proportion of tunnel settlement in each stage is summarized. Through numerical simulation, the influence of linear shrinkage of shield on the rationality of numerical simulation modeling is analyzed, and the influence of key construction parameters of large-diameter slurry shield on surface settlement deformation is comprehensively analyzed. The research results can provide reference for the design and construction of large-diameter slurry shield.

  Comments: Chapter 5 looks more like conclusions than discussions.

5. Response: According to your suggestion, we have changed the title of section 5 from 'discussion' to 'conclusion'.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The reviewer appreciates the prompt actions taken by the authors to address the comments and suggestions raised during the first round of the review process. The reviewer accepts most responses to comments and suggestions. However, the reviewer suggests that the authors avail of any English editing service, as the revised version of the manuscript has several grammatical errors, which can confuse the potential readers of the paper if it is accepted for publication. If it is impossible to avail of the service, the reviewer suggests that the authors carefully proofread the paper. From lines 50 through 51, kindly use lowercase for 'formation' and 'width'. The soil properties in Table 2 also need to be defined either as footnotes. The reference list format is not following the MDPI style. The reviewer suggests looking at other published papers in Buildings for proper referencing style.

Author Response

We are very grateful to the reviewers for your comments on the manuscript, which enables us to further improve the quality and format of the paper. Each suggested revision and comment, brought forward by the reviewers were carefully considered and corrected.

1. Comments: The reviewer appreciates the prompt actions taken by the authors to address the comments and suggestions raised during the first round of the review process. The reviewer accepts most responses to comments and suggestions. However, the reviewer suggests that the authors avail of any English editing service, as the revised version of the manuscript has several grammatical errors, which can confuse the potential readers of the paper if it is accepted for publication. If it is impossible to avail of the service, the reviewer suggests that the authors carefully proofread the paper. From lines 50 through 51, kindly use lowercase for 'formation' and 'width'. The soil properties in Table 2 also need to be defined either as footnotes. The reference list format is not following the MDPI style. The reviewer suggests looking at other published papers in Buildings for proper referencing style.
2. Response: Thank you very much for your valuable comments. We have revised the relevant contents of the paper according to your comments, and checked and revised the language and grammar of the full text of the paper. This is very helpful to improve the readability and scientificity of the paper.

Author Response File: Author Response.docx