The Face Stability Analysis of Shield Tunnels Subjected to Seepage Based on the Variational Principle
Round 1
Reviewer 1 Report
Dear Sirs,
I accepted the publication for review, but I had some doubts as I am not an expert in technical matters related to the construction of tunnels, but rather rock deformations. Nevertheless, I checked the text from the scientific point of view and I concentrated on issues related to the aspects which are more familiar to me. So, the manuscript entiled “The Face Stability Analysis of Shield Tunnels Subjected to Seepage Based on Variational Principle” by Zhihui Zhou, Tonghua Ling, Fu Huang and Min Zhang represents a good research level. The authors present a certain analytical approach and they applied professional software to make numerical simulations related to safety of engineering work (stability of the tunnel) and disturbances in hydrogeological conditions (underground water seepage).
However I have some remarks and there are some correction in the text.
The author uses several times “a great influence”. For example: “The parameter analysis indicates that the groundwater seepage has a great influence on the range of the collapse surface for the shield tunnel face” and in the abstract. Will you inform readers what is a size o that “great influence” (for you and the others as well?). This is a technical text, so express your results more technically.
According to the authors “For calculation simplicity, some assumptions of the failure mechanism are presented…”. This is important information. The text would be much stronger if you took in your analysis other types of stratum. There would be a certain spectrum of “great influence”, so there will be something to be compared.
Figures are OK. But please complete them adding description of the plots’ axes. Each axis should be clearly labeled with the quantity that is being plotted and units.
In my opinion all figures and tables should be in the text. It is much better to the readers. Well, they certainly should not separate the conclusions and the reference chapters.
So I have no objections to the presented content of the manuscript but the conclusions should be more specific, not generalized and there should be some considerations about what has been done, what the authors' contribution to the problem has been, and what they think needs to be done.
I suggest some corrections in the text. The text is written in very good English. There are only some corrections, just to make a higher quality level of the manuscript….The corrections in the text are mostly to be considered (to make the text clear) and there are some do be done (errors). So, just open the attachment and look at them, please.
Comments for author File: 
Comments.pdf
Author Response
We would like to express our sincere thanks to the reviewer 1 for the constructive and positive comments. Point by point responses to the reviewer’ comments are listed below.
Replies to Reviewer 1
- The author uses several times “a great influence”. For example: “The parameter analysis indicates that the groundwater seepage has a great influence on the range of the collapse surface for the shield tunnel face” and in the abstract. Will you inform readers what is a size o that “great influence” (for you and the others as well?). This is a technical text, so express your results more technically.
Answer: The description of the “a great influence” can be explained as follows. We investigated the effect of underground water seepage on the collapse range of the soil in the front of the shield tunnel face in our manuscript. As can be seen in Fig.7, the shapes of the collapse surface with consideration of seepage and without consideration of seepage are plotted. Fig.7 shows that the collapse range under the consideration of seepage effect is about 0.2 m larger than the condition without consideration of seepage when other parameters are the same. Comparing with the condition without consideration of seepage, the effect of groundwater seepage on the stability of the shield tunnel face is great. Thus, we mentioned that the “the groundwater seepage has a great influence on the range of the collapse surface for the shield tunnel face” in our manuscript. Moreover, the precise description of the influence is added in the revised manuscript.
Figure 7. Effect of groundwater seepage on collapse surface of tunnel face.
- According to the authors “For calculation simplicity, some assumptions of the failure mechanism are presented…”. This is important information. The text would be much stronger if you took in your analysis other types of stratum. There would be a certain spectrum of “great influence”, so there will be something to be compared.
Answer: We have investigated the influence of different parameters on the shape of collapse surface for tunnel face in section 5. In this section, the shapes of collapse surface for tunnel face corresponding to the parameters γ=7.5kN/m3, L=10 m, H=10 m, σT=18kN, σt=0, σc=10~100kPa, A=0.4~0.7, β=33°~66° are plotted. As mentioned in section 3.3, is a material constant characterizing the soil or rock mass and is the uniaxial compressive strength of the soil or rock mass. The different values of parameter A and σc represent the different geological characteristics of stratum. Thus, we have considered the application of our method in types of stratum.
- Figures are OK. But please complete them adding description of the plots’ axes. Each axis should be clearly labeled with the quantity that is being plotted and units. In my opinion all figures and tables should be in the text. It is much better to the readers. Well, they certainly should not separate the conclusions and the reference chapters.
Answer: The reviewer’s comment is reasonable. The units have been added in each axis, which can be seen in the Figure 3-Figure 7 of the revised paper. All figures and tables are in the text, which can be seen in the revised paper. Moreover, the conclusions and the references are not separated in the revised paper.
- I suggest some corrections in the text. The text is written in very good English. There are only some corrections, just to make a higher quality level of the manuscript….The corrections in the text are mostly to be considered (to make the text clear) and there are some do be done (errors). So, just open the attachment and look at them, please.
Answer: We would like to express our sincere thanks to the reviewer 1 for his (her) constructive and positive comments. We have read the attachment carefully and revised the text based on the reviewer’s suggestion.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The detailed comments can be found in the word file uploaded.
Comments for author File: Comments.pdf
Author Response
We would like to express our sincere thanks to the reviewers for the constructive and positive comments. Point by point responses to the reviewers’ comments are listed below.
Replies to Reviewer 2
- More references and research results in the last five years should be provided in the manuscript.
Answer: The reviewer’s comment is reasonable. Some latest studies corresponding to our issue have been added in the revised paper.
- The variable “σT” should be italic in section 2.
Answer: The reviewer’s comment is reasonable. The variable “σT” has been replaced by “σT” in section 2.
- The issue numbers of some references were missed. The authors should add issue numbers in these references.
Answer: The reviewer’s comment is reasonable. All the missing issue numbers have been added in the references
Reviewer 3 Report
The study of tunnel face stability when excavating in complex stratum under the water table have great engineering significance. By using upper bound theorem and variational approach, the authors obtained the analytical expression of the collapse surface for the tunnel face. Given the above consideration, I think their work could be suitable for publication in Sustainability after some revisions.
However, there are some problems presented below should be clarified by the authors:
1. The first letter of sentence “The first integration” in line 213 should be lowercase;
2. The authors mentioned software MATLAB, however, this software is not added in the reference.
3. In the introduction, the literature review is incomplete. The authors do not provide a detailed, satisfactory review of previous studies. Authors should also state clearly what improvements upon previous relevant studies have been made.
4. Further English editing is necessary as there are so many grammatical, paragraphing, and punctuation errors in the text. The author was advised to send the manuscript to a native English speaker for a review of grammar and vocabulary.
Author Response
We would like to express our sincere thanks to the reviewers for the constructive and positive comments. Point by point responses to the reviewers’ comments are listed below.
Replies to Reviewer 3
- The first letter of sentence “The first integration” in line 213 should be lowercase.
Answer: The reviewer’s comment is reasonable. This mistake has been revised in the revised paper.
- The authors mentioned software MATLAB, however, this software is not added in the reference.
Answer: The reviewer’s comment is reasonable. The reference corresponding to software MATLAB has been added in the revised paper, which can be seen reference [18].
- In the introduction, the literature review is incomplete. The authors do not provide a detailed, satisfactory review of previous studies. Authors should also state clearly what improvements upon previous relevant studies have been made.
Answer: Some latest studies corresponding to our issue have been added in the introduction of the revised paper. So, the introduction of the revised paper can reflect the latest achievements of the stability analysis of a shield tunnel face with the consideration of groundwater seepage.
Furthermore, the existing studies of this issue focus on the stability of a shield tunnel face. We proposed a theoretical method to calculate the collapse region of the tunnel face induced by an insufficient cabin pressure under the water table here. This is the first time that an analytical expression of the collapse surface of a shield tunnel face is derived with consideration of the effect of seepage. Thus, the proposed method can provide the collapse region of the soil in the front of the tunnel face, which is useful for the stability assessment of a shield tunnel excavated under the water table.
- Further English editing is necessary as there are so many grammatical, paragraphing, and punctuation errors in the text. The author was advised to send the manuscript to a native English speaker for a review of grammar and vocabulary.
Answer: The reviewer’s comment is reasonable. To improve the language, flow, grammar, and clarity of the manuscript, we invited a native English speaker to proofread the document. The resubmitted edition has been revised by the native English speaker and expert in the field. We believe that all the grammar errors in our manuscript have been corrected.
Author Response File: Author Response.docx
