Numerical Simulation of Ultra-Shallow Buried Large-Span Double-Arch Tunnel Excavated under an Expressway

Round 1

Reviewer 1 Report

This paper took Xiamen Haicang super-shallow-buried large-span double-arch tunnel as research object.  The excavation process of three pilot tunnels and three-bench reserved core soil method of the ultra-shallow buried large-span double-arch tunnel with fault fracture zone under a running highway was simulated by using the numerical analysis software FLAC3D. The paper is good and the issue is very current. Some specific comments are listed as follows:

 

Detailed comments:

Title is too long, please shorten it.

 

Abstract: the abstract is very long with many trivial details. I recommend the authors to rewrite the abstract as follows: 1) The gap or the problem in the present state, 2) methodology used to solve the problem, and 3) key points and results of the present research. The length of the abstract should be around 150 to 200 words.

 

Introduction: In introduction, there are too few references cited, and more references are needed. You need to mention and discuss the recent publications in the field of arch tunnels, e.g., (Tunnelling and Underground Space Technology. 103(2020), 103465. Doi: 10.1016/j.tust.2020.103465.).

 

Please also discuss the loading on arch during construction and if possible, please compare it with that from analytical method (e.g. Tunnelling and Underground Space Technology. 103(2020), 103465. Doi: 10.1016/j.tust.2020.103465.).

The tenses of the article are confused and need further improvement.

Material parameters should be described in more detail.

What does tunnel mouth represent in Figure 5?

The degree of torsional deformation of the partition wall should be described in detail.

Conclusions need to be improved, what is the most important conclusion from this research? What is the next step of your research?

 

The authors need to conduct a thorough proofreading before resubmitting.

# In Line 113, “which” >> “whch”.

# In Line 124, “ultra shallow ” >> “uliyra shallow”.

# In Line 416, “140 m. Due to ” >> “140 m.Due to”.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The article contains important information regarding the stability of underground workings. The biggest advantages of the article are numerical researches on vertical deformation of surface and surrounding rock during excavation of main tunnel. The performed numerical tests seem to be important for ensuring the effectiveness of tunnel construction in the two-way system. Below are some comments and suggestions.

1. In the introduction, it should be mentioned that the monitoring of the behavior of the rock mass between two workings can be performed with the use of string sensors (doi: 10.3390/ en13112998);
2. In the second Chapter, I would suggest adding a lithological profile with marking of the layers in which the excavations will be made; this would significantly increase the value of the research;
3. In the third Chapter , it should be written how the fault zone was defined: 20 m and 60 degrees;
4. Line 170 "... long pipe sched ...." , it should be written what was the length and how the elements were installed;
5. Line 310, it should be corrected the sentence: "… ..pilot tunnel. and… ”.
6. For the results of the support displacement presented in sections 4.2.2 and 4.2.3, it should be written what are the permissible values;
7. In the chapter on Conclusions, two or three sentences should be added regarding the results of numerical modeling, which indicate the places of increased deformation and take a possible method of strengthening the excavation.

Author Response

Please see the attachment.

Author Response File: Author Response.docx