Determination of Supporting Time of Tunnels in the Xigeda Stratum Based on the Convergence-Confinement Method

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The study proposes the New Austrian Method as execution technology. On the paper’s content there is no reference over the execution steps for which the numerical simulations were considered. Please specify in your paper if you took into account all stages of the NATM method or only the last stage, when the entire tunnel cross section was complete.

The second question: how did you took into consideration the rock load and the tunnel weight? There are no references over the geometrical elements of the cross section – please refer in your paper the thickness of the tunnel’s cross section and how you took into calculus the rock pressure and tunnel load.

Author Response

Comments 1: The study proposes the New Austrian Method as execution technology. On the paper’s content there is no reference over the execution steps for which the numerical simulations were considered. Please specify in your paper if you took into account all stages of the NATM method or only the last stage, when the entire tunnel cross section was complete.

Response 1: Thank you for your comments. We mentioned the NATM method to introduce the Convergence- Confinement  Method. The CCM method is a theoretical method developed with the maturity of the NATM methond, especially the concept of interaction between surrounding rock and support. Indeed, the purpose of numerical simulation is to obtain the LDP curve, and the LDP curve is the deformation curve of the tunnel in the open hole state, which means we don't use the NATM method in numerical simulation.

Comments 2: How did you took into consideration the rock load and the tunnel weight? There are no references over the geometrical elements of the cross section – please refer in your paper the thickness of the tunnel’s cross section and how you took into calculus the rock pressure and tunnel load.

Response 2: We are greatful for your comments. The thickness of the tunnel’s cross section is 1m. As for rock pressure and tunnel load, the vertical stress is simulated by the self-weight stress field, and the lateral stress coefficient is set to 0.5.  We have added relevant contents in the manuscript.

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Editors and Authors,

Thanks for this opportunity to review this manuscript.

In this work, the influence of the water content on the longitudinal deformation of the surrounding rock at a certain distance from the tunnel excavation face was analyzed. Based on the convergence-confinement principle, the time at which support should be applied was estimated. The Convergence-Confinement Method was developed by Terzaghi in the 1940s. The method takes into account the interaction between the ground and the tunnel lining, providing an estimation of the deformation and stress distribution in the surrounding soil and support structure. Over time, this method has been expanded to include non-circular tunnels and has become a widely accepted approach in geotechnical engineering. It allows engineers to assess the stability of the tunnel during construction and predict potential ground movements, ensuring safe and efficient tunneling operations.

The manuscript can be published if the authors presented well the following comments:

1. It is well known that in conditions of variation (increase) of humidity, especially predominantly clayey rocks, exhibit a pronounced deformation behavior.

2. It is also known that the presence of clay rocks or a layer of clay (even a thin layer) can considerably change the conditions of tension and implicit deformation around the underground work, leading to a significant extension of the relaxation both in the direction of the vault as well as the arch bottom. As stated in this manuscript, the Xigeda layer (which consists mainly of gray-green clay rock, gray-black clay rock, gray-yellow clay rock, silty clay rock, and siltstone).

3. Line 68: instead of "hard rick" it will be corrected "hard rock"

4. What is the difference between the curves in figure 6 and the curves in figure 7? Both figures show the LDP curves under different water content conditions. In fact, they are identical; only the scale of representation on the abscissa axis differs.

5. Where is the support mounted? On line 340, you write, "the support should be applied at 1.46 m in front of the excavation face." And on line 352, you write that "the best support time is 1.5m behind the working face." It is correct: behind the excavation front, at 1.5 m.

6. This manuscript is filled with well-known descriptions.

In my opinion, the paper can be accepted for publication after the authors respond to the comments made.

Yours faithfully,

Comments on the Quality of English Language

Minor editing of English language required

Author Response

Comments 1: It is well known that in conditions of variation (increase) of humidity, especially predominantly clayey rocks, exhibit a pronounced deformation behavior.

Response 1: Thank you for your suggestion. We have added relevant contents in the manuscript.

Comments 2: It is also known that the presence of clay rocks or a layer of clay (even a thin layer) can considerably change the conditions of tension and implicit deformation around the underground work, leading to a significant extension of the relaxation both in the direction of the vault as well as the arch bottom. As stated in this manuscript, the Xigeda layer (which consists mainly of gray-green clay rock, gray-black clay rock, gray-yellow clay rock, silty clay rock, and siltstone).

Response 2: Thank you for your suggestion. We have added relevant contents in the manuscript. 

Comments 3: Line 68: instead of "hard rick" it will be corrected "hard rock"

Response 3: Thank you for pointing out the word spelling errors. We have corrected the misspelled words.

Comments 4: What is the difference between the curves in figure 6 and the curves in figure 7? Both figures show the LDP curves under different water content conditions. In fact, they are identical; only the scale of representation on the abscissa axis differs.

Response 4: Thank you for your comments. We listed figure 7 to focus on the deformation of the excavation face. Indeed, it is part of Figure 6, and we have modified the figures to make it more readable.

Comments 5: Where is the support mounted? On line 340, you write, "the support should be applied at 1.46 m in front of the excavation face." And on line 352, you write that "the best support time is 1.5m behind the working face." It is correct: behind the excavation front, at 1.5 m.

Response 5: Thank you for pointing out our mistakes. We have modified the relevant content. 

Comments 6: This manuscript is filled with well-known descriptions.

Response 6: Thank you for your suggestion. We have adjusted the language style.

Reviewer 3 Report

Comments and Suggestions for Authors The main question of the article is using numerical simulation and numerical analytical methods for determination of supporting time of tunnel in Xigeda stratum. Topic of this article relevant in the field.

It's interesting scientific research. But,  I have some comments. 

1. I think that the abstractat  at the end it is necessary to add the meaning of the obtained results and how to use them further.

2. The graphs in the fig. 5,6,7 are not very readable. It's advisable to increase them.

3. I guess that conclusions should be more specific with regard to the numerical results that are obtained.

Author Response

Comments 1: I think that the abstractat  at the end it is necessary to add the meaning of the obtained results and how to use them further.

Response 1: Thank you for your suggestion. We have added the relevant contents in the manuscript.

Comments 2: The graphs in the fig. 5,6,7 are not very readable. It's advisable to increase them.

Response 2: Thank you for your suggestion. We have modified the figures to make it more readable.

Comments 3:  I guess that conclusions should be more specific with regard to the numerical results that are obtained.

Response 3: Thank you for your suggestion. We have added the relevant contents in the manuscript.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Editors and Authors,

Thank you again to the editor for giving me the opportunity to review this paper. I appreciate the correct answers given by the author(s).

Yours faithfully,