Three-Dimensional Numerical Modeling of Artificially Freezing Ground in Metro Station Construction

Round 1

Reviewer 1 Report

In the reviewed article, numerical modeling of the process of soil strengthening during the construction of subway lines by artificial freezing is considered. The research topic is relevant and has important applications in the construction of underground structures.

The authors have analyzed approaches to solving the problem in sufficient detail, which is reflected in the list of literary sources and their description.

The article provides a detailed design scheme, identifies the problems of engineering implementation of the process of creating a curtain of frozen soil in real conditions of the Nanning metro line 3.

Based on the three-dimensional finite element modeling in the ADINA program, the conclusions are obtained:

- On the good coincidence of the results of numerical simulation with instrumental measurements of the temperature field;

- About the need to change the freezing scheme at the top of the bell, where the downhole tunnel crosses the connecting passage;

- About the development of the freezing zone in time.

The numerical results obtained for the analysis of the temperature field presented in the article are sufficient for the practical solution of the problem.

There are comments on the article:

1. In the Methodology section, when setting the task, you should also specify how the conditions were set on the outer boundary of the domain

2. It is necessary to clarify the parameters of modeling the phase transition to the frozen state. Figure 5 shows that the freezing rate (slope of the curves) according to the model and measurements are different in the range from 0 to -2 degrees C. Obviously, a correction of the model is required in this area.

3. As a wish for the development of work in the future. Of interest is the calculation of mechanical stress fields in the freezing area, as well as the possibilities of the FEM-calculation program to optimize the number of freezing holes, their location and length.

 If the comments are eliminated, the article can be accepted for publication in the journal Applied Sciences.

Author Response

Please refer to the attached file.

Author Response File: Author Response.pdf

Reviewer 2 Report

Please consider the following comments while preparing the revised manuscript:

1. Though the topic is novel and of interest for the audience, the quantum of work seems insufficient required for the journal article. Moreover, the discussions pertaining to the observations are very weak. The authors should focus on these aspects based on which the decision will be made for the particular submission.

2. The significance of each parameter described as a part of the work must be well described.

3. Keywords should be very specific to the scientific requirement of the study. Revise and present the keywords again.

4. Specify the significance of Table 1 presented in the introduction section.

5. Is the novelty of the work related to site specific? Why not the authors validate their results of FE study with the similar ones available in the literature.

6. Figure 1 is meaningless (without markings) and is to be strongly improved.

 

Author Response

Please refer to the attached file.

Author Response File: Author Response.pdf

Reviewer 3 Report

REVIEW

on article

Three-Dimensional Numerical Modelling of Artificially
 Freezing Ground in Metro Station Construction

Bo Wang, Jun Hu, Xiaoqi Lin and Hui Zeng

 

SUMMARY

The article submitted for review is relevant. The article presents a three-dimensional numerical modelling of artificially freezing ground in metro station construction. The authors created a three-dimensional model, which made it possible to study the temperature change in the frozen soil thickness with the simulation of dynamic development. The numerical model was tested, the weakest points were determined using the calculation scheme, and a quantitative characteristic of the result obtained was given. The practical application of the scientific result is the possibility of building an underpass, which can be used in the construction of the subway. Thus, the authors made up for a certain scientific and practical deficit. This article is original and practically significant. However, the article has a number of serious shortcomings, they need to be corrected.

 

COMMENTS

1.    The Abstract needs to be improved. The authors did not formulate the specific problem they were solving. It remains unclear why the research was carried out, how the numerical three-dimensional model was developed. Will it be better than the existing tools for modeling artificial soil freezing during the construction of a metro station? This must be clearly justified, indicating the scientific deficit, respectively, the scientific novelty and practical significance of the study. The authors should finalize the Abstract.

2.    It is not entirely clear in the Abstract which methods were used by the authors. If these were numerical methods, then you need to list them using specific references in the middle of the abstract. In the context presented, the abstract does not meet the requirements of the Journal.

3.    The next note is the list of keywords. It should be noted that we are also talking about modeling metro stations. The authors did not indicate this in keywords. Probably, the article will be of interest to both metro builders and metro designers, but due to the lack of keywords, they will not be able to find it.

4.    The "Introduction" section looks incomplete, as there are not enough references to the sources that the authors analyzed. The fact is that the modeling of metro stations, soil freezing are a widespread well-known topic in the scientific literature, and the authors should have carried out a deeper analysis. It is necessary to supplement the literature review by expanding the number of sources to 30-35. In its current form, the analysis looks very poor.

5.  Table 1 seems interesting, but may need some expansion or additional explanation. It is necessary to clearly formulate the purpose, tasks and scientific novelty of the study.

6.   In Section 2, the diagrams in Figures 1-3 need further explanation.

7.    What do the auxiliary lines in Figure 1 mean?

8. Tables 2 and 3 look very cumbersome, they require an explanation. Authors should provide a detailed explanation of these tables so that the article is easily perceived by readers.

9.    The model in Figure 4 should be explained in more detail. Boundary conditions and loading conditions are not specified.

10.Figure 4 shows that some elements have degenerate geometry: too sharp corners and uneven side proportions. This can lead to incorrect calculation results.

11.If you give several views on the Figure, they should be labeled (a) and (b). The captions should include explanations.

12.References are given in square brackets, for example, [1], not as a superscript.

13.The graphs in Figure 5 are not entirely clear, they need additional explanation and analysis. In addition, some characters on them are unreadable, too small. Authors should think about the graphical representation of these graphs, perhaps a color version of the presentation of graphical results should be used, because they are difficult to distinguish. The same remarks apply to Figures 6-8, that is, the authors should submit the figures larger, in good resolution, and enlarge the characters that are not visible. In their current form, they are simply not perceived by the naked eye.

14. The discussion of the obtained results is not fully presented. Authors should compare their results with those of other authors in more detail.

 

15. Conclusions need a clearer formulation of the scientific result from a qualitative and quantitative point of view, as well as in determining the prospects for the development of the study and a more specific indication of the scope of the result obtained. As mentioned earlier, references to the literature in the amount of 23 sources are not enough, at least 30-35 sources on the research topic should be submitted. Only then will it be possible to talk about scientific novelty and the current state of the issue. In this case, preference should be given to sources from the last five years.

Author Response

Please refer to the attached file.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Most of the comments were addressed.

Reviewer 3 Report

All my comments were taken into account and appropriate corrections were made in the manuscript.
I recommend the article for publication.