Seismic Behavior of Micropiles and Micropiled Structures Used for Increasing Resilience: A Literature Review

Round 1

Reviewer 1 Report

This is a good-written introductory paper on application of MPs. However, the scientific depth of the full paper needs to be well improved. There is little innovative contents in terms of analysis and research work on MP itself as well as MP related structures. Specific comments include: 1) Some part of the paper are just listing contents cited from code/standard or stating some obvious common knowledge. Usually readers are more willing to get innovative contents from such scientific research papers, which cannot be read from codes or text books. 2) The study on literature collection in this paper is still insufficient and incomplete.This article covers too many aspects related to MPs, so that each problem can only involve a few literatures, so the analysis on each topic isn't completed. As a result, the scope of the full text is too broad and the depth is insufficient. 3) In particular, there is too little literature on experimental test and numerical simulation work on MPs, which is the key part in this research field. The 5th chapter only lists some articles. The authors haven't made well study and summary on these papers and no innovative foundings can be achieved.

Author Response

Dear reviewer,

Thank you for the opportunity to submit a revised draft of our manuscript titled “Seismic behaviour of Micropiles and Micropiled Structures used for increasing resilience. A Literature Review”.

We are really appreciating the time and effort that you dedicated for providing a very useful and valuable feedback. Also, we would like to thank you for the appreciations formulated on our review work.

We have been able to incorporate changes to reflect most of the suggestions provided by the reviewers and these are highlighted in the manuscript. 

Here below you can find answers to your comments and questions.

Comment #1: However, the scientific depth of the full paper needs to be well improved.

Answer: Thank you for this comment. The paper has been deeply revised on this matter. For each of the studied aspects in the paper we have added more explanations, details and arguments, as well as more synthetic compilation and analysis of the data found in the literature, including personal remarks and conclusions. We are considering that, based on your comments, we have been able to further increase the scientific level of our paper and to provide useful syntheses and analyses on the topic for the readers.

Comment #2: There is little innovative contents in terms of analysis and research work on MP itself as well as MP related structures.

Answer: Based on your comment we understood that the already existing innovative content in the paper wasn’t well emphasized and also that we need to add further personal and innovative contributions.

We carried out a major revision of the paper on this aspect:

• A better highlight of the personal contribution – the authors own compilations and analyses of the data found in the literature and the authors’ new proposed association and connection details between MPs and base isolator systems
• More synthetic data have been added, including several compilations, analyses and personal conclusion performed by the authors
• More graphs compiled by the authors have been included

We are considering that the revised paper is of higher quality, it is including by far more personal contributions on the understanding of the MPs behavior and, more important, of what is further needed for a comprehensive knowledge. This is of a major importance for the readers, who can now find in this review paper a lot of useful data for their further studies.

Comment #3: Some part of the paper are just listing contents cited from code/standard or stating some obvious common knowledge. Usually readers are more willing to get innovative contents from such scientific research papers, which cannot be read from codes or text books.

Answer: Thank you for this comment. As mentioned here above, the paper has been completely revised for improving this aspect:

• We reduced to the minimum necessary the introductive, well-known part, which can be found in the codes
• We added more references, more innovative content, synthetic data and compilations, graphs and analyses of the existing data.

Comment #4: The study on literature collection in this paper is still insufficient and incomplete. This article covers too many aspects related to MPs, so that each problem can only involve a few literatures, so the analysis on each topic isn't completed. As a result, the scope of the full text is too broad and the depth is insufficient.

Based on your valuable comment, a major revision was carried out on this aspect. 10 more references have been added and for the existing ones more in depth and detailed analysis and presentation was included in the paper, along with personal remarks and compilations of the existing data.

We consider that now the seismic behavior of MPs is more completely presented, based, of course, on the existing data in the literature, but we are also underlined the missing aspects, the gaps and the needs for further research.

Only the seismic behavior is treated in the paper, by means of experimental and numerical analyses found in the literature. We explained better in the text that some aspects are beyond the scope of this paper, as for example the static behavior of MPs or the specific aspects of seismic dampers (only the association with MPs is the scope of our paper).

Comment #5: In particular, there is too little literature on experimental test and numerical simulation work on MPs, which is the key part in this research field. The 5th chapter only lists some articles. The authors haven't made well study and summary on these papers and no innovative findings can be achieved.

Answer: Thank you for this comment. We performed a major revision of the modelling chapter (now chapter 4, former chapter 5). Many additional references have been included and analyzed in detail, we provided a summary of selected papers with our own remarks and a synthesis of the influential factors with the main findings and our own conclusions.

We consider that now the paper is completely treating all aspects of the modelling of MPs. 

Reviewer 2 Report

Dear authors,

This manuscript covers a thorough literature review related to the seismic behaviour of micropiles and micropile structures to enhance resilience. I am sure that this work will be a good contribution for the scientist working/analysing the detail work.

I am suggesting the acceptance of the manuscript in the current form

Author Response

Dear reviewer,

Thank you for the opportunity to submit a revised draft of our manuscript titled “Seismic behaviour of Micropiles and Micropiled Structures used for increasing resilience. A Literature Review”.

We are really appreciating the time and effort that you dedicated for providing a very useful and valuable feedback. Also, we would like to thank you for the appreciations formulated on our review work.

We have been able to incorporate changes to reflect most of the suggestions provided by the reviewers and these are highlighted in the manuscript. 

We are submitting a revised and improved version of our paper which is enhancing further the scientific level.

Reviewer 3 Report

In this literature review, the authors firstly introduce the Micropiles and Micropiled Structures, then presented relevant information about MPs, as technology, seismic behavior, applications for increasing seismic resilience, numerical modeling and etc. Overall impression from paper is positive and research outcomes have practical value.

However, there are still some comments for corrections:

1. In Section 3.1, “[1] presents some common drilling techniques”, it is suggested to add the name of this reference before [1].
2. “O. Heo et al. [15] confirmed...”, “O.” can be deleted.
3. “A. Ghorbani et al. [11] performed”, “A.” can be deleted.
4. In Figure 5, the size of front is too small to read.
5. There are too many complex sentences in the manuscript. It is suggested to use short sentences instead.
6. The format of references is inconsistent. Please improve.

Author Response

Dear reviewer,

Thank you for the opportunity to submit a revised draft of our manuscript titled “Seismic behaviour of Micropiles and Micropiled Structures used for increasing resilience. A Literature Review”.

We are really appreciating the time and effort that you dedicated for providing a very useful and valuable feedback. Also, we would like to thank you for the appreciations formulated on our review work.

We have been able to incorporate changes to reflect most of the suggestions provided by the reviewers and these are highlighted in the manuscript.

Here below you can find answers to your comments and questions.

1. In Section 3.1, “[1] presents some common drilling techniques”, it is suggested to add the name of this reference before [1].

Answer: Thank you for drawing the attention, this has been corrected.

2. “O. Heo et al. [15] confirmed...”, “O.” can be deleted.

Answer: Thank you for drawing the attention, this has been corrected.

3. “A. Ghorbani et al. [11] performed”, “A.” can be deleted.

Answer: Thank you for drawing the attention, this has been corrected.

4. In Figure 5, the size of front is too small to read.

Answer: Thank you for drawing the attention, this has been corrected.

5. There are too many complex sentences in the manuscript. It is suggested to use short sentences instead.

Answer: Thank you for this comment, we improved the expression in the text.

6. The format of references is inconsistent. Please improve.

Answer: Thank you for drawing the attention, this has been corrected.

Reviewer 4 Report

The paper presents a review of the seismic behaviour of Micropiles and Micropiled structures, that could be employed for the retrofitting of old buildings and/or for new resilient buildings. The topic has been developed by describing micropiles classification, technology, seismic behaviour, modelling strategies. In the reviewer opinion, the paper deals with an interesting and actual topic, and could be accepted for publication, after an improving of the discussion (section 6), where future developments should be discussed in more detail. In general, the paper is reasonably well written and organized, though a systematic editing (see for example row 515) could improve the language fluency and the clarity of the paper.

Author Response

Dear reviewer,

Thank you for the opportunity to submit a revised draft of our manuscript titled “Seismic behaviour of Micropiles and Micropiled Structures used for increasing resilience. A Literature Review”.

We are really appreciating the time and effort that you dedicated for providing a very useful and valuable feedback. Also, we would like to thank you for the appreciations formulated on our review work.

We have been able to incorporate changes to reflect most of the suggestions provided by the reviewers and these are highlighted in the manuscript.

Here below you can find answers to your comments and questions.

Comment #1: In the reviewer opinion, the paper deals with an interesting and actual topic, and could be accepted for publication, after an improving of the discussion (section 6), where future developments should be discussed in more detail.

Answer: Thank you for this comment, based on your opinion we have carried out a major revision of the paper by including more references, more analyses and comments for each aspect, also some more personal contributions on compiling and analyzing the data found in the literature. Also have been better emphasized the personal contributions and proposals. We have also included more graphs and tables. Section 6 (currently 5) – Discussion has been significantly revised, although the discussions have been included in each chapter and paragraph, but we put in this section the main aspects that resulted from the analysis.

Comment #2: In general, the paper is reasonably well written and organized, though a systematic editing (see for example row 515) could improve the language fluency and the clarity of the paper.

Answer. Thank you for your comment. We revised the whole paper also from this point of view.

Round 2

Reviewer 1 Report

The article has been comprehensively revised. All issues concerned by the reviewer have been explained. All suggested amendments have been implemented. The scientific and innovative nature of the article has been improved. It is suggested to publish this paper.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

This paper presents a comprehensive  literature review about the seismic behavior of Micropiles foundation and seismic damper systems. It is very interesting since, to my knowledge, it is the only one and thus should be very useful for the earthquake, the geotechnical and the civil engineering scientific community. 

This paper is of great quality, is very well written, easy to read, and based on the very recent studies on the topic. I have only few observations that could improve the manuscript a little :

• line 220 : authors should describe a bit more in detail the "structure dynamic amplification factor". How does the micropiles enhance the dynamic response of the structures ? In what frequency band ? How was it measured ?
• line 260 : similarly to my first observation : what is the frequency band for which a decrement of the foundation input motion is usually observed ? Is there never any constructive interference between waves diffracted by the kinematic soil-structure interaction ?
• line 292 : How can the increase of rigidity of the soil when using Micropiles have a bad impact on the structure seismic response ?
• line 299 : Where do the authors see a double enhancement when combining Micropiles and a paper system ?
• Numerical modelling : it seems that the only considered seismic solicitations are body waves travelling more or less vertically under the foundations. Could the authors comment about the limitation of these hypothesis in regards of the surface waves that can also be an important solicitation of these foundations ? What is the impact on the response of the foundation-structure behavior ?
•  

 

Author Response

Dear reviewer,

Thank you for the opportunity to submit a revised draft of our manuscript titled “Seismic behaviour of Micropiles and Micropiled Structures used for increasing resilience. A Literature Review”.

We are really appreciating the time and effort that you dedicated for providing a very useful and valuable feedback. Also, we would like to thank you for the appreciations formulated on our review work.

We have been able to incorporate changes to reflect most of the suggestions provided by the reviewers and these are highlighted in the manuscript.

Here below you can find answers to your comments and questions.

Comment 1: line 220: authors should describe a bit more in detail the "structure dynamic amplification factor". How does the micropiles enhance the dynamic response of the structures? In what frequency band? How was it measured?

Comment 2: line 260: similarly to my first observation: what is the frequency band for which a decrement of the foundation input motion is usually observed? Is there never any constructive interference between waves diffracted by the kinematic soil-structure interaction?

Answer: Thank you for pointing this out. Micropiles (MPs) influence on the dynamic response of the structures was generally detected as a function of the displacement response, modification of the natural period, or the inertial forces of these structures. Unfortunately, the frequency band is not clear for all the papers discussed; but it is globally assumed that the measurement was performed for both broad-band and narrow-band, as in some papers are reported to be performed dynamic pile load test, while others performed numerical analysis to study the behavior of MPs excited by either a harmonic motion or by a real earthquake record.

Regarding the kinematic soil-structure-interaction, it will indeed have a strong influence on the behavior; this influence is generally assumed to be positive, but also minor or even negative influence can be obtained, as the outcome of the interaction is not only a function of the soil and MPs only, but also depends on the seismic source.

We have added some more elements in the manuscript regarding these points.

Comment 3: line 292: How can the increase of rigidity of the soil when using Micropiles have a bad impact on the structure seismic response?

Answer: Thank you for your question. In our opinion, increasing the stiffness of the soil will lead to an increase in the rigidity of the system (soil-MPs-structure), and depending on the excitation source, this can move the seismic response away or closer from resonance. We hope that this is answering to your question. We introduced some more lines about this point in the revised manuscript.

Comment 4: line 299: Where do the authors see a double enhancement when combining Micropiles and a paper system?

Answer: Thank you for pointing this out, maybe this was not sufficiently explained in the paper. We added some more explanations in the revised manuscript. The double enhancement we are considering is “decoupling” and “increasing damping value”, seismic dampers can do both of them or mainly “decoupling” (for base isolators); here MPs can either help in increasing damping value, which develops these basic base isolators from only a “decoupling” solution into a “decoupling + increasing damping” solution, also they can be used to optimize base isolators, taking into consideration the increase in damping value that they potentially provide. Or they can influence the decoupling phenomenon itself, indirectly by influencing the input motions, which can also lead to an optimization in the base isolators. These topics are aimed to be studied by the authors in the future.

Comment 5: Numerical modelling : it seems that the only considered seismic solicitations are body waves travelling more or less vertically under the foundations. Could the authors comment about the limitation of these hypothesis in regards of the surface waves that can also be an important solicitation of these foundations ? What is the impact on the response of the foundation-structure behavior ?

Answer. We are agreeing with this comment and we have introduced new text clarifying this point. It is true that the focus of the discussed topics in the paper was on the body waves, even so the foundation will be excited by both types. By taking into consideration the two possibilities that exist: body waves arrive before surface waves, or intersecting of body and surface waves. From the point of view of the authors, MPs role can be useful in decreasing the potential hazard of the “softening” phenomenon which is related to the difference of seismic waves arrival. This can be achieved by:

-           Potential 1: Influencing the damping value.

-           Potential 2: Influencing the stiffness value.

-           Potential 3: Surface waves are also subjected to kinematic interaction as well as body waves.      

The final impact is a function of all these three potentials, and the optimum solution exists as an equilibrium between the influence on damping, stiffness, and the influence on kinematic interaction; it is aimed to study the influence of each of these potential factors individually, and then develop a complex study to finally reach the optimum solution that can be useful in real life. We hope that the new introduced text is clarifying this point for the readers.

 

In addition to the above comments, we reviewed the manuscript for any other spelling and grammatical errors. 

Reviewer 2 Report

The paper can be accepted.

Author Response

Dear reviewer,

Thank you for the opportunity to submit a revised draft of our manuscript titled “Seismic behaviour of Micropiles and Micropiled Structures used for increasing resilience. A Literature Review”.

We are really appreciating the time and effort that you dedicated for providing a very useful and valuable feedback. Also, we would like to thank you for the appreciations formulated on our review work.

We have been able to incorporate changes to reflect most of the suggestions provided by the reviewers and these are highlighted in the manuscript.

Reviewer 3 Report

The paper has not well written.

Abstract has poorly written. It should be rewritten.

Is the Base isolation accounted in the Literature review of the Micropiles??

There are lots of published papers in case of Base isolation. Only a few papers have been cited in this paper.

More new and relevant papers should be added to this paper.

What is the aim and scope of the paper? The reviewed papers should be collected around the aim of the paper.

 

 

Author Response

Dear reviewer,

Thank you for the time and effort that you dedicated for providing a very useful and valuable feedback.

We have been able to incorporate changes to reflect most of the suggestions provided by the reviewers and these are highlighted in the manuscript.

Here below you can find answers to your comments and questions.

Comment 1: Abstract has poorly written. It should be rewritten.

Answer: Thank you for your suggestion. We revised the abstract in order to be more clear what is the focus of the paper, which is micropiles and micropiled structures and their seismic behaviour.

Comment 2: Is the Base isolation accounted in the Literature review of the Micropiles?

Answer: Thank you for this comment and suggestion. It would have been interesting to explore also this aspect, but in the case of our manuscript the base isolation was only included to discuss the idea of the association with micropiles, therefore it is slightly out of our scope.  

Comment 3: There are lots of published papers in case of Base isolation. Only a few papers have been cited in this paper. More new and relevant papers should be added to this paper.

Answer. Thank you for your suggestion. We agree that seismic dampers generally, and base isolators specifically have a lot of ongoing researches, and every year there are new papers that are added. The cited papers were only chosen to illustrate some main concepts of base isolation that we considered as useful for the topic of their association with MPs. To better illustrate the idea and to enrich the text, more referenced papers have been cited in the revised version of the manuscript.

Comment 4: What is the aim and scope of the paper? The reviewed papers should be collected around the aim of the paper.

Answer: Thank you for your question. The aim of the paper is to provide a literature review of the seismic behavior of MPs and discussing the possibility of capitalizing on MPs to enhance the seismic behavior of structures. Seismic dampers were addressed in the paper only to present the idea of associating them with MPs, which represent one of the possibilities of enhancing the seismic behavior. Also retrofitting historical structures with MPs and base isolators is an interesting subject, that was included in the scope. We  revised the text in order to be more clear about this point.

In addition to the above mentioned comments we revised the manuscript in order to avoid any mispelling or grammatical errors. 

Round 2

Reviewer 3 Report

The paper has not been revised based on the reviewer's comments. Therefore, it is not suggested to publish.

Author Response

Dear reviewer,

Thank you for the time and effort that you dedicated for providing a very useful and valuable feedback.

We have been able to incorporate changes to reflect most of the suggestions provided by the reviewers and these are highlighted in the manuscript.

Here below you can find answers to your comments and questions.

Comment 1: Abstract has poorly written. It should be rewritten.

Answer: Thank you for your suggestion. We revised the abstract in order to be more clear what is the focus of the paper, which is micropiles and micropiled structures and their seismic behaviour.

Comment 2: Is the Base isolation accounted in the Literature review of the Micropiles?

Answer: Thank you for this comment and suggestion. It would have been interesting to explore also this aspect, but in the case of our manuscript the base isolation was only included to discuss the idea of the association with micropiles, therefore it is slightly out of our scope.

Comment 3: There are lots of published papers in case of Base isolation. Only a few papers have been cited in this paper. More new and relevant papers should be added to this paper.

Answer. Thank you for your suggestion. We agree that seismic dampers generally, and base isolators specifically have a lot of ongoing researches, and every year there are new papers that are added. The cited papers were only chosen to illustrate some main concepts of base isolation that we considered as useful for the topic of their association with MPs. To better illustrate the idea and to enrich the text, more referenced papers have been cited in the revised version of the manuscript.

Comment 4: What is the aim and scope of the paper? The reviewed papers should be collected around the aim of the paper.

Answer: Thank you for your question. The aim of the paper is to provide a literature review of the seismic behavior of MPs and discussing the possibility of capitalizing on MPs to enhance the seismic behavior of structures. Seismic dampers were addressed in the paper only to present the idea of associating them with MPs, which represent one of the possibilities of enhancing the seismic behavior. Also retrofitting historical structures with MPs and base isolators is an interesting subject, that was included in the scope. We revised the text in order to be more clear about this point.

In addition to the above mentioned comments we revised the manuscript in order to avoid any mispelling or grammatical errors.