Characteristics of Dynamic Safety Factors during the Construction Process for a Tunnel-Group Metro Station

Round 1

Reviewer 1 Report

The current study investigates the deformation in the vicinity of 3 parallel underground excavations. For this purpose, the authors use the Finite Element (FE) method as modeling approach. The study also reports some settlement data obtained in the field. I am rejecting the paper at this time since there are several shortcomings, as detailed below.   

General consideration: the work looks like a consulting report, NOT a scientific article (see, e.g., the conclusion section).

Shortcomings:

• Line 34: Why can't FEM be used to determine FS for tunnel projects?
• In the introduction, there is an evident lack of previous studies that used FEM simulations for the excavation of tunnels. This lack of an adequate literature review is reflected in the results section (there was no connection with other works).
• Line 89: Many sentences are not clear (e.g., line 89, lines 94-98). How can the investigated method predict a progressive rupture?
• I've never seen a summation like the one placed in the denominator of equation 3. k and i and are being added from 1 to 1?
• It is very difficult to understand the methodology of the work. No assumptions were provided for estimating the model parameters (the model was poorly described in the text, by the way).
• Grammar should be improved significantly. See, citing just a few, line 160 (“The both”), lines 237, 241, 252, 255, 269, and several others
• What would be analytical conditions of section 3.3? This is not even mentioned in the rest of the work.
• In section 3.4, field observations are compared with numerical simulations. The result seems to be excellent. But how was the model calibrated to obtain such a fit?
• The term Kinetic Change of FS (section 4) seems inappropriate. Wouldn't it be dynamic variation of the FS with the constructive process? This section refers to the results of numerical simulations. However, a number of issues were not even mentioned in the methodology. For example, what would be excavation area 5? What construction steps are those represented in figure 11? How will the reader know if an excavation was supported or not?

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

The article addresses an important and very interesting topic of the characteristics of kinetic safety factor during construction process of a tunnel-group metro station, which is appreciated. The study includes the numerical research. In this paper the research on tunnel stability mainly focuses on the overall safety factor of tunnels under different surrounding rock or buried depth. The research results in the kinetic change of safety factor of tunnel-group during the whole construction period are few. Therefore, this paper attempts to apply the strength reduction method to the kinetic change of safety factor during construction of tunnel-group metro station, and the displacement of construction and the equivalent plastic strain of the surrounding rock under different working conditions are analyzed. The Reviewer has some concerns regarding the introduction, description of numerical models, results, conclusions and references. Generally, in this paper the English language is good, but some sentence should be more clear. Please check the text of Native Speaker. In opinion of Reviewer this paper should be subjected to major revision.

Other comments:

1. Please explain more clear what differences are between your research and previous research cited in the text (more detailed)? In addition, please explain what is novelty of your research? Generally, this introduction is too short.
2. The introduction is really poor. Where is the state of the art? Where is description of similar research? Please look at this paper of the introduction:

• https://doi.org/10.3390/ma14164493
• https://doi.org/10.3390/ma14164493
• https://doi.org/10.1016/j.soildyn.2021.107005

3. The structure of this paper is not correct. Below you can see the structure in the scientific paper:

• Introduction,
• Methodology,
• Description of research,
• Results,
• Discussion of results,
• Conclusions,
• References.

This structure of article is more clearly and recommended in scientific papers. In current version is not clear.

4. Detailed descriptions of numerical model (tunnel - RC, use analysis, which program was used) should be added. e.g. https://doi.org/10.3390/ma14164493
5. Please show the boundary conditions in numerical models. This aspect is very important due to the correct updating numerical models with experiment. Please improve it.
6. The discussion of results is really poor. Where is the discussion of the results with compare to other similar research? Please add.
7. Please improve the conclusions, because of in current version are poor. What is the general conclusion from this research? What is the next step of your research? Please explain the tendency from your research. In addition, please select the most important conclusions using bullets.
8. The references are really poor. Please add some papers of similar research. Only 20 references are too small in scientific paper. Please improve it.

And the end I hope that my comments will be helpful for the authors.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

First, I could not observe the responses to my comments. This makes my judgment difficult as important questions remain unanswered.

1. For instance, it is very difficult to understand the methodology of work. no assumptions were provided for estimating the model parameters (which was poorly described in the text, by the way).
2. A critical question, that could differentiate the article from others previously published is the calibration of the numerical simulations, which remains unclear. That is, field observations are compared with numerical simulations. The result seems to be excellent. But how was the model calibrated to obtain such a fit?

The conclusions have no connection with the results of the work:

3. Did the authors introduce the strength-reduction finite element method for tunnels? (line 301)
4. The authors do not report when there was convergence (or not) of the finite element method. So why would convergence be a finding of the work? (line 311)
5. More importantly, at no time was it commented on how the safety factor was changed during the construction process (the main goal of the paper).

Additionally, regarding the increase in article references, some of them could not be identified on the internet (e.g., ref [26])

Author Response

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Reviewer 2 Report

Thank you for your improving but the Reviewer has some concerns regarding the introduction, description of numerical models and references. Generally, in this paper the English language is good, but some sentence should be more clear and in addition please use the passive voice. Please check the text of Native Speaker. In opinion of Reviewer this paper should be subjected to major revision.

Other comments:

1. The introduction is really poor, because of the most literature come from China Researchers (this is not acceptable in scientific paper). Below you can find some papers about steel tunnels (maybe some papers will be interested for you).

• https://doi.org/10.1016/j.engstruct.2019.109358
• https://doi.org/10.1016/j.tust.2020.103808
• https://doi.org/10.1016/j.tust.2021.104346
• https://doi.org/10.1016/j.tws.2022.108884
• http://dx.doi.org/10.12989/scs.2018.27.2.217
• https://doi.org/10.1007/s40891-020-00232-z

2. Please show the boundary conditions in numerical model. I cannot find this picture in your paper. Please improve it.
3. The references are really poor, because of the most literature come from China Researchers (this is not acceptable in scientific paper).

And the end I hope that my comments will be helpful for the authors.

Author Response

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Author Response File: Author Response.docx

Round 3

Reviewer 2 Report

Thank you for your improving. One final note: please change the Figure 3. Please add the numerical model with correct boundary conditions (right side should be have another direction of boundary condition).

 

Author Response

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Author Response File: Author Response.docx