Numerical Simulation on the Response of Adjacent Underground Pipelines to Super Shallow Buried Large Span Double-Arch Tunnel Excavation

Round 1

Reviewer 1 Report

Reviewer’s comment: Numerical simulation on the response of adjacent underground pipelines to super shallow buried large span double-arch tunnel excavation

Summary

The authors have undertaken an extensive study on Numerical simulation on the response of adjacent underground pipelines to super shallow buried large span double-arch tunnel excavation. The paper contains an extensive detail. An objective discussion, comparison and conclusions are made on their observations. As a result, it will be valuable to the scientific community. The following specific comments are provided to further refine the manuscript.

Detailed comments

• Lines 112-115: Provide specific objectives of this research in this section.
• Line 163: This section on establishment of numerical models should be linked to existing literature. Further, provide more justifications in this section.
• Table 1: Provide additional justification on how material parameters were chosen.
• The conclusions seem shallow. Provide more details in this section.

Author Response

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Reviewer 2 Report

In this manuscript, a numerical simulation has been provided to investigate the response of adjacent underground pipelines because of tunnel excavation. The idea of this work is interesting; however, the manuscript should be revised totally to validate the numerical simulation and discuss the results. 
1- The introduction should be revised by reviewing relevant papers so that the novelty of this work is highlighted. 
2- A theoretical background should be presented for this study.
3- In Fig. 1, the left section is not clear.
4- in page 3, it seems that the pipelines have been divided into two categories: rigid and flexible. The authors should define these categories. 
5- Experiments or other verified results should verify the results of numerical simulation. 
6- The boundary conditions and type of loading should be explained more. 
7- In Fig. 4, add a magnification from the portal section. 
8- Please explain why the settlement of symmetric pipelines relative to pipeline 1 is different.
9- What important information was added by Fig. 7 to Fig. 6.
10- It is suggested to study the effects of other loading types, such as traffic loads. 
12- Why do the settlement amounts usually converge at the end of distance (60 m).
13- Why settlement of thicker pipelines is more than thinner ones.
14- it is expected that square pipelines cause greater stress concentration; does this considered in the presented results.
15- The type of soil could have a significant effect on the settlement of pipelines. Please discuss it in this study. 
16- It is expected that optimum conditions and a guideline are presented as a conclusion.

 

 

Author Response

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Reviewer 3 Report

Only minor comments.

1. Figs. 2 and 3 are so unclear and very small. Please improve them.

2. More details on FEM should be added. 

3. Number of meshes and the boundary conditions of the model in Fig. 4 should be given.

4. Figs. 6 and 7 are also difficult to see.

5. More references regarding the use of finite element method for tunnels should be added as:

• - Design equation for stability of shallow unlined circular tunnels in Hoek-Brown rock masses.
• - Undrained stability of unlined square tunnels in clays with linearly increasing anisotropic shear strength
• - Support pressure for circular tunnels in two layered undrained clay
• - Stability of unsupported circular tunnels in anisotropic normally and over consolidated saturated clay
• - Peripheral stability of circular tunnels in anisotropic undrained clay  

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The reference of Eq. 1 and 2 should be added to the manuscript.
Several Figures such as 7, 8, and 10 have been shown twice.

Author Response

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Author Response File: Author Response.pdf