Deformation and Stress Analysis of Pile-Supported Immersed Tunnels under Seismic Loads
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
Comments on the manuscript ‘Stability Analysis of Sand Compaction Pile-Immersed Tunnel Seawater System under Incident Seismic Waves’ (Ref:applsci-2638391)
In this work, the authors have studied the deformation pattern of sand compacted piles in immersed tunnels due to seismic induced loads through finite element analysis and carried out some parametric studies to evaluate the effect of various parameters on the response of the piles. The reviewer has the following comments.
1. Title: The title doesn’t reflect the content of the paper and should be changed. The paper focuses on FE analysis of deformation and stresses in the tunnel and the piles, whereas the title is ‘stability analysis’. The suggested title is ‘Deformation and stress analysis of pile-supported underwater tunnels due to seismic loads’
2. The type of FE analysis carried out to evaluate the seismic response is not clear. There are two types of analysis for these types of problems, i.e., time history analysis and response spectrum analysis. I think the authors carry out time history analysis here. Please clarify and introduce a discussion to this effect in the paper.
3. The steps of analysis should be mentioned clearly. Fig. 4 should come first in the paper. The solid model should be shown. Right now, only the FE model is shown. The pile foundation in the soil bed should be shown, including the depth of pile modeled in the soil. The boundary conditions should be shown clearly. It is mentioned that finite springs and dampers are considered at the boundaries to model infinite soil (Page 5, line 136-140). It is okay to model like this. However, the extent of soil that is modeled should be mentioned. Moreover, the results of convergence analysis should be presented in this paper in order to demonstrate that the finite extent of FE model as used in this analysis truly represents the infinite soil. This is missing from the results and discussion.
4. Section 2.2.1: This is not ‘constitutive model’. It should be ‘FE mesh and boundary conditions in the analysis’.
5. Fig. 3: Where is the acceleration vs time data? This should be provided.
6. Line 105-106, page-4: Where do you get value of peak acceleration as 0.05g and damping ratio of 0.05? These acceleration data are not shown in Fig. 3.
7. Table 1: Please provide units of all physical quantities, e.g., surface area, Es etc. How are models M1, M2 and M3 different? Why 3 models are used? Please discuss.
8. Provide source of Fig. 3.
9. Fig. 1: How is Fig. 1(a) obtained? Please discuss.
10. Fig. 2 is not necessary and it may be removed.
11. What are breaking strain and baking stress in Fig. 1(a)? It only shows axial pressure vs displacement during compression test.
12. Page-5, line 147: Equations should be written in equation format, not as inline equation.
13. Table-2: What is the source of these data? Have you evaluated yourself or taken from some reference? Please provide reference.
14. Equations 3 to 6 in page-7 are well known. These may be removed. Provide appropriate reference instead.
15. Equation 7 and 9: How do you get data regarding the last term, i.e., sigma_b_ff ? Please elaborate. This is a crucial input to the analysis.
16. Most of the figures are hazy and not legible. Example: Figs. 6,7,8 etc.
17. Fig. 6: How are data points for ‘settlement’ measured? What is the physical instrument used? Please elaborate. Why are there so many scatter in data. You have fitted a line. It really doesn’t fit the scatter and the scatter is very large. Can we say that the simulation matches with experiment? The authors should clarify this point by including a discussion in the paper.
18. Fig. 6(d): Why is there no scatter in acceleration data? Where is it measured? Please plot results of experiment and FE analysis together. Why is the peak in numerical result shifts to the right and it doesn’t match with measurement? Please discuss.
19. Fig. 7: What are the contours on the right hand margin? Is it maximum principal or principal stress? What is x-axis, i.e, its physical significance? Where is the location of these stresses? Please show it in the model.
20. Fig. 8: What are the two curves for each set? L & R? Is the deformation symmetric about the line?
21. Fig. 10: Strain is ‘unit-less’. It is shown as ‘mm’ in Fig. 10. Please be consistent with the terms. Please check if it is in %age.
22. Fig. 11: The p-y curves as obtained from the analysis should be compared with experimental data, if available. Please elaborate on this. What is the validity of these results? Please include a discussion to this effect. The authors may refer some literature results in order to justify these results.
23. Fig. 12: Why is displacement vary so much at the depth of 2m, whereas the displacement values become almost same at higher depths? Please include a discussion.
24. Conclusions: The conclusions should be shortened. Only relevant conclusions should be included. Please explain also the reason for each conclusion. For example, conclusion 3 should be supported by proper arguments.
25. Abstract: It should be shortened and re-written. Remove the last 2 lines as these are ambiguous at the beginning. Don’t use p-y value in the abstract. Define it first.
26. References: Please include literature on advances in seismic analysis procedures and the latest developments.
27. There are many grammatical mistakes in the paper. Please correct these in the revised manuscript.
Comments on the Quality of English Language
1. There are many grammatical mistakes in the paper. Please correct these in the revised manuscript.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for Authors
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* Review comments for applsci-2638391-peer-review-v1 *
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This paper examined the sand compaction pile-immersed tunnel-seawater (SIS) system's stability when exposed to seismic waves using the finite element method. The study also validated its numerical results through physical modeling. The study showed that seawater has a greater effect on tunnel frequency suppression as the depth increases. Moreover, the sand pile replacement rate ranges from 50% to 62%, and the partition wall's damping enhancement in the immersed tunnel also suppresses the tunnel response frequency. Nonetheless, the analysis indicated that the variation of the immersed tunnel frequency might cause structural resonance damage on the tunnel's far side from the seismic wave source. This resonance shifts the peak stresses in the immersed tunnel towards the wave source, with the distance of movement twice as much on both sides as in the center. Additionally, the research discovered that seawater depth variation had a more significant influence on the P- γ values at the pile's roof than the pile end, while the pile slenderness ratio (γ) had the opposite effect. If the gravel cushion is damaged in tension, γ = 9.37; if it's damaged by pile piercing, γ = 15.
Overall, the paper is well-prepared and the results are presented and discussed in a clear manner. However, in the next revision, it is important to focus on addressing the following major issues that need to be improved:
1. It seems that the authors did not effectively communicate the originality of their work in their presentation. The novelty of their work was not clearly demonstrated and it is questionable! Commonly, in the last paragraphs of the Introduction section, the novel features of the work are displayed by the authors based on the current literature and other authors’ works.
2. In the first paragraph of the Introduction section, the authors use “intrinsic frequency”! Do they mean “fundamental frequency”? The statement “intrinsic frequency” has been solely utilized in the literature and should be appropriately modified. In addition, the authors have been not mentioned what kind of fundamental frequencies of the tunnel are of their major concern: longitudinal, radial, or circumferential frequencies. By this view, the authors are advised to reconsider on the above-mentioned issues in this paragraph and other sections of the present article.
3. In Figs. 1, 3, 5, and 8-12, in the x-label and y-label parts of most of these figures, there should be inserted a free space between the main given statements and the “(unit)”. As it is obvious, in most cases, there is no free spaces between them, making them somehow unreadable.
4. What is the significance of the stress variation after the earthquake in the design scheme of the immersed tunnel? How does seawater depth affect the stresses on the tunnel bottom and roof plate under seismic excitation? What is the significance of the stress peaks occurring on both sides of the roof and bottom plates of the tunnel? How does the change in sand compaction pile (SCP) arrangement affect the stress peaks of the roof and bottom plates?
5. What is the damping effect of the structure itself on the seismic wave and how does it impact the design scheme of the immersed tunnel? Please clarify in some detail within your manuscript.
6. For structural analysis of the piles and their interactions with the nearby medium (soil), they are commonly modeled based on the Euler-Bernoulli, Timoshenko, and higher-order beam theories, and for taking their interactions with the nearby soil, the soil is modeled by an elastic layer with one or two parameters (i.e., Winkler or Pasternak foundation model). For lower levels of the slenderness ratio, the role of the shear deformation on the obtained results become important and the necessitate to shear deformable beam models is highly required, particularly when the interactions of the pile with the surrounding elastic soil will be considered. By this virtue, the authors are encouraged to display this crucial effect in the paper as well.
7. Under the given Comment~6, there are some numerical models in the literature based on the meshless methods (EFG, RKPM, and so on) that have been developed for static, buckling, and vibrational analyses of beam-like elements with the Pasternak foundation layer (like the understudy piles here). In this regard, the following works can be explained by the authors in the paper:
- https://doi.org/10.1007/s11012-015-0184-2.
- https://doi.org/10.1016/j.engstruct.2021.112453.
- https://doi.org/10.1007/s11012-014-9957-2.
- https://doi.org/10.1016/j.compositesb.2018.08.089.
- https://doi.org/10.1016/j.amc.2014.01.015.
- https://doi.org/10.3390/sym15101827.
8. It seems that the prediction results by the numerical model are given in the lack of inertia effect of tunnel structure, piles, and other parts. Is this true? Please explain in more detail.
9. Regarding the proposed numerical scheme, which has been introduced in Subsection 2.2.1, I have some concerns as follows:
- The phrase “cells” should be modified to “element”, since it seems that that the authors are employing a finite element-based approach for their analysis.
- The authors display that “C3D8P cells were considered for foundation and pile consolidation drainage, while C3D8R cells with reduced integration and hourglass control were used for tunnels, gravel cushions, and backfill.”; however, the characteristics these elements (number of nodes, shapes) are not explained. Are these being all rectangular-cubic elements? Please explain in some detail.
- It seems no treatment has been taken into account at the interface of the soil and the piles to appropriately consider their interactions (please also see Comment~6).
- In the demonstrated graph for the overall view of the schematically illustrated numerical model, the level of the water and the kind of immersed tunnel is not exactly clear! Please revise that appropriately.
- The type of boundary conditions
10. The convergence of the proposed numerical scheme (i.e., finite element-based methodology) has been explained and researched for the problem at hand. Could the authors provide some graphs to show the effectiveness of the performed calculations through examining the convergence check of the proposed numerical scheme for a special case?
11. The given relations for the proposed numerical model are somehow superficial! No inertia effect, no explicit deformation expression, no explicit stress statement, and more! In fact, no analytical expressions for dynamic elastic fields of the medium due to seismic waves are given. So, in the lack of these issue and under the umbrella of comment~8, the exactness of the proposed numerical model is somewhat questionable!
12. For appropriate modeling of a group of vertical piles, a group of embedded beam-like elements (i.e., multiple beams with vertically aligned configurations) adjacent to each other from macro to nano has been not appropriately acknowledged. To this end, the authors are expected to explain the following works on the deformation of beam-like structures accounting for their lateral interactions and considering the effect of the surrounding medium (i.e., by employing the Winkler or Pasternak foundation model):
- https://doi.org/10.1007/s00707-014-1107-3.
- https://doi.org/10.1155/2018/5103174.
- https://doi.org/10.1016/j.physb.2014.04.044.
- https://doi.org/10.1016/j.tws.2021.107688.
- https://doi.org/10.1016/j.camwa.2018.02.033.
- https://doi.org/10.1016/j.ijmecsci.2018.06.018.
13. What is the SCP-reinforced marine foundation and how does it work? What is the optimum slenderness ratio for the SCP-reinforced marine foundation? Which factors influence on this optimum value? Please explain that with more detail.
14. How can the findings of this study be applied to future construction projects for better structural/geotechnical resistance? Please explain in the paper.
15. The future works have been not explained by the authors. Since this paper will be read by interested scholars, giving some crucial guidelines for some important and hot issues will be surely beneficial.
16. The text’s English suffers from grammatical errors and style typos, in which some of these mistakes are listed as follows:
ü Line 14, “Modelling” à “Modeling” (please note that “Modelling” represents a non-American variant and it should be written in the context of the American English spelling).
ü Line 21 and other parts of the article, “Centre” à “Center” (please note that “Centre” represents a non-American variant and it should be written in the context of the American English spelling).
ü Line 267, “in order to” à “to” (the phrase in order to is somewhat wordy and thereby it should be suitably reconsidered).
ü Lines 12, 13, 59, and 60: “Sand Compaction Pile-Immersed Tunnel-Seawater (SIS)” à “sand compaction pile-immersed tunnel-seawater (SIS)” (there is no need to use first capital letters for the constitutive words of this expression).
ü There are some wordy/lengthy sentences that should be suitably split into shorter ones.
ü There are some badly constructed sentences, from both grammatical and technical points of view, that should be suitably revised.
As is seen, the whole paper should be carefully checked against various errors and typos.
If the authors can answer the questions raised in a rational manner, I can review the revised version of the paper again and provide further comments if necessary. However, if the questions are addressed properly, I may recommend the paper for publication. At this stage, it is highly recommended for the authors to focus on addressing the technical issues and providing their technical answers and modifications in the paper.
Comments on the Quality of English Language
The text’s English suffers from grammatical errors and style typos, in which some of these mistakes are listed as follows:
ü Line 14, “Modelling” à “Modeling” (please note that “Modelling” represents a non-American variant and it should be written in the context of the American English spelling).
ü Line 21 and other parts of the article, “Centre” à “Center” (please note that “Centre” represents a non-American variant and it should be written in the context of the American English spelling).
ü Line 267, “in order to” à “to” (the phrase in order to is somewhat wordy and thereby it should be suitably reconsidered).
ü Lines 12, 13, 59, and 60: “Sand Compaction Pile-Immersed Tunnel-Seawater (SIS)” à “sand compaction pile-immersed tunnel-seawater (SIS)” (there is no need to use first capital letters for the constitutive words of this expression).
ü There are some wordy/lengthy sentences that should be suitably split into shorter ones.
ü There are some badly constructed sentences, from both grammatical and technical points of view, that should be suitably revised.
As is seen, the whole paper should be carefully checked against various errors and typos.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for Authors
Dear authors,
Congratulations on this work. The subject is an interesting one and for actuality.
Some necessary corrections:
Remove or change Figure 2. The current photos don’t add any value to the paper. Maybe a schema for the installation will be better.
The quality of the figures must be improved. Increase the resolution. In some cases, the text is hard to read, and for some figures the points or lines are difficult to distinguish.
Leave space between values and their measurements units, ex. Line 16, 271, 272, 343 and so on.
Change the symbol for degree to be like 7 ° (line 281, and others).
Line 421 the correct order it is “and end”.
Best regards,
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for Authors
The authors have addressed all the comments in the revised version of the manuscript and it may be accepted for publication in the journal.
Author Response
Dear reviewer
Thanks very much for the reviewer's comment. The research background references were added. The research methodology and design options were more fully described. Improved language writing. Thanks again for signing the reviewer's comment.
Yours sincerely
All author
Reviewer 2 Report
Comments and Suggestions for Authors
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* Review comments for applsci-2638391-peer-review-v2 *
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Thank you to the authors for your responses and revisions. I carefully read through all of the responses to the queries raised in the previous round of review. While some of the responses were helpful, there were a few cases where I couldn't find appropriate responses. Overall, I would give my current score a 6 out of 10. However, I did review the revised manuscript again based on the new revision and wanted to provide my feedback in the following comments. If the responses to my feedback are addressed rationally and technically, I will reconsider my decision; otherwise, the paper will not be accepted:
1. The present study suffers from inclusive parametric studies. Indeed, the roles of some factors on the settlement, displacement of the tunnel support, and principal stresses of the tunnel in the presence of three sets of pile foundations (rectangular, diagonal, and plum blossom piles) have been distinctively investigated but the performed parametric studies were limited to several seawater levels, height of vertical support, specific SV wave, and so on. Can the authors provide a more deep and inclusive parametric study to reveal their interactional roles in the structural response of the tunnel, generalizing the results of the present study for further investigations in this field?
2. It is indeed mentioned in the paper that only shear waves have been considered for the analyses, and the influence of incident P-waves or shear horizontal (SH) waves has not been investigated. It is not clear from the paper if the authors have a specific reason for this investigation orientation, as it is not explicitly mentioned. However, it is possible that the authors wanted to focus on the influence of shear waves on the structural response of the tunnel and linked piles, as they may be the dominant type of wave for this particular scenario. Do the authors have a specific reason for such an investigation orientation?
3. It is worth noting that the paper does not discuss the relevance of deep learning, neural network, and artificial intelligence methodologies in resolving engineering dilemmas. These techniques have proven to be highly effective in dissecting intricate problems, and their omission in the paper is a matter of concern. Herein, a combination of seawater depth, characteristics of incident waves, geometry and location (depth, orientation, and so on), interactions between the tunnel and the nearby soil, properties of soil, and piles’ characteristics can affect the maximum principal stress of the tunnel, horizontal displacement, and settlement. For generalizing the soil-structure-wave analysis, it can be beneficial that a comprehensive parametric study is conducted to determine the role of each above factors on the mechanical response of the structure, and these data are understood by the machine through special algorithms. Therefore, incorporating deep learning-based references in future research will benefit the readers immensely and enhance the value of the study. In this regard, the authors should explain such crucial approaches by displaying the following recent works:
- Deng, Y., Zeng, Z., Jha, K., & Huang, D. Problem-based cybersecurity lab with knowledge graph as guidance.
- Khan, J., Lee, E., Kim, K.: A higher prediction accuracy–based alpha–beta filter algorithm using the feedforward artificial neural network.
- Jiang, T., et al.: Wavelet method optimised by ant colony algorithm used for extracting stable and unstable signals in intelligent substations
- Hu, X., Kuang, Q., Cai, Q., Xue, Y., Zhou, W., & Li, Y. A coherent pattern mining algorithm based on all contiguous column bicluster.
- Wang, H., et al.: An improved bearing fault detection strategy based on artificial bee colony algorithm.
- Jia, Z., Wang, W., Zhang, J., & Li, H. Contact high-temperature strain automatic calibration and precision compensation research.
4. How the material properties of different layers of soils can be reasonably introduced to the beam-like element of piles, arriving at more rational solutions and results? Please explain that based on the technical evidence and reasons in the manuscript of the paper as well.
5. In the case of a sinusoidal propagating wave or earthquake wave, the variation of seawater can have a significant impact on the maximum horizontal and vertical displacements of piles. The wave-induced forces acting on piles are strongly influenced by the variation of seawater, which in turn affects the amplitude and frequency of the wave motion. As for the effect on the curve of maximum acceleration in terms of the period, a change in seawater variation can cause alterations in the shape and timing of the acceleration curve. This is because the acceleration curve is dependent on the wave period, and changes in the wave period will result in a shift of the curve. Additionally, changes in the seawater variation can affect the frequency content of the wave, leading to changes in the acceleration curve. Therefore, it is important to consider the variation of seawater when analyzing the behavior of piles under wave-induced forces.
For a given sinusoidal propagating wave or earthquake wave, how does the variation of the seawater influence the maximum horizontal and vertical displacements of piles? How such a variation could alter the curve of maximum acceleration in terms of the period?
6. It seems that all the performed analyses are given for an individual earthquake loading, while at least 2-3 wave/earthquake analysis of the problem is required to arrive at the most general results and explanations. It is suggested that multiple wave/earthquake analyses of the problem are required to arrive at the most general results and explanations, as the presented analyses are given for an individual earthquake loading.
7. The presented Equations (4) and (5) are almost the same. Do the authors want to express two sets of equations or an error has occurred? Please check it carefully.
8. In Figure 8, the presented colormap bar at the right-hand side of the subfigures (a)-(c) is useless and it should be deleted.
9. There are still some technical errors and grammar typos in the manuscript. For example,
- In Figs. 11(a)-(c): The y-label’s expression (i.e., “y(m)”) must be changed to “y (m)” (i.e., a free space before the first parenthesis must be considered). Please also check the other figures against this fault.
- In Figs. 13(a)-(c): The present y-label’s expression (i.e., “Displacement(m)”) must be changed to “Displacement (m)” (i.e., a free space before the first parenthesis must be considered). Please also check the other figures against this fault.
- In Fig. 6: The present caption should be modified to “Normal velocity and normal displacement time history curves on the surface of the numerical model: (a) bottom surface, (b) side surface.”
- Line 212: The statement “He, C et al [46]” must be changed to “He et al. [46]” (ONLY “surname of the first author” + “et al.”, indicating “, C” should be deleted and “et al” should be changed to “et al.”); Line 209: The statement “Keivan Kiani [43,44]” must be changed to “Kiani [43,44]” (ONLY surname should be given), and “B.A. Selim [45]” must be modified to “Selim and Liu [45]” (there exist two authors in reference [45], and therefore, their surnames should be connected by “AND”); Line 160: “Kou, K.P [33]” must be modified to “Kou and Yang [33]” (please see the above comment on this modification). Please also all the style of the references cited in the paper based on the above modifications.
- In the whole manuscript: The statement “"H" shaped” should be changed to “H-shaped”.
I advise authors to recheck the entire manuscript against many existing errors, as some of them are now provided above, and then also get consultant on the English language from native editor or professional editing companies.
If the authors can answer the questions raised in a rational manner, I can review the revised version of the paper again and provide further comments if necessary. However, if the questions are addressed properly, I may recommend the paper for publication. At this stage, it is highly recommended for the authors to focus on addressing the technical issues and providing their technical answers and modifications in the paper.
Comments on the Quality of English Language
There are still some technical errors and grammar typos in the manuscript. For example,
- In Figs. 11(a)-(c): The y-label’s expression (i.e., “y(m)”) must be changed to “y (m)” (i.e., a free space before the first parenthesis must be considered). Please also check the other figures against this fault.
- In Figs. 13(a)-(c): The present y-label’s expression (i.e., “Displacement(m)”) must be changed to “Displacement (m)” (i.e., a free space before the first parenthesis must be considered). Please also check the other figures against this fault.
- In Fig. 6: The present caption should be modified to “Normal velocity and normal displacement time history curves on the surface of the numerical model: (a) bottom surface, (b) side surface.”
- Line 212: The statement “He, C et al [46]” must be changed to “He et al. [46]” (ONLY “surname of the first author” + “et al.”, indicating “, C” should be deleted and “et al” should be changed to “et al.”); Line 209: The statement “Keivan Kiani [43,44]” must be changed to “Kiani [43,44]” (ONLY surname should be given), and “B.A. Selim [45]” must be modified to “Selim and Liu [45]” (there exist two authors in reference [45], and therefore, their surnames should be connected by “AND”); Line 160: “Kou, K.P [33]” must be modified to “Kou and Yang [33]” (please see the above comment on this modification). Please also all the style of the references cited in the paper based on the above modifications.
- In the whole manuscript: The statement “"H" shaped” should be changed to “H-shaped”.
I advise authors to recheck the entire manuscript against many existing errors, as some of them are now provided above, and then also get consultant on the English language from native editor or professional editing companies.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 3
Reviewer 2 Report
Comments and Suggestions for Authors
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* Review comments for applsci-2638391-peer-review-v3 *
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Thank you to the authors for your responses and revisions. I carefully read through all of the responses to the queries raised in the previous round of review and I am pleased to “Accept” this version of the paper.
I noticed a minor issue with the reference styles of some of the references included in the body of the article. It's important to double-check them in accordance with the reference list to ensure accuracy and consistency. For instance, some modifications that could be made include:
- Line 44: “Zhao, W et al. [10]” à “Zhao et al. [10]” since just the surname of the first author is sufficient.
- Line 45: “Yang, Y.B. et al. [11]” à “Yang and Zhou [11]” since Ref. [11] has two authors and their surnames should be connected through “and”.
- Line 52: Kiani et al. [19] à Kiani [19] since Ref. [19] has only a single author.
Just a quick note to let you know that as an author and a reviewer, it is highly encouraged that you check all of your work and make any necessary revisions to ensure accuracy and clarity of the English and references.
