Seabed Liquefaction around Pipeline with Backfilling Trench Subjected to Strong Earthquake Motions

Round 1

Reviewer 1 Report

The paper examines the effect of trench backfilling on the residual liquefaction around pipeline and the induced uplift of pipeline under the joined action of earthquake and ocean wave and current loading. In my opinion the paper is original, However, it seems major revision is needed before accepting it for publication in its current form due to the following reasons.

COMMENT 1 the main problem is that the manuscript doesn’t include a satisfactory guideline in sec. 4 and should be further explained.

COMMENT 2 Please, check again the manuscript for typos and grammatical errors, e.g. in Abstract “uplift of pipeline under the combined action of earthquake and ocean wave and current loading” is better to be “earthquake, ocean wave and current loading”. Or “ can be expressed as follows”. and etc.

 

COMMENT 3 benchmark data for validation part should be refereed and clarified.

 

COMMENT 4 regarding the fig 3 maybe the necessity of this work is better to be highlighted in the introduction.  

Author Response

Response: Thanks for sparing time to review the manuscript. We appreciate the positive comments. We have carefully addressed all the comments in this response as well as in the revised manuscript. Please note that all changes are marked red in the revised manuscript. The reference is also updated accordingly. Our responses are summarized as follows.

COMMENT 1: the main problem is that the manuscript doesn’t include a satisfactory guideline in sec. 4 and should be further explained.

Response: As suggested, a guideline has been added in Sect. 4 before discussing the results. Furthermore, Sect. 4 has been subdivided in order to improve the understandability. Please see the details in the Lines 208-212.

COMMENT 2: Please, check again the manuscript for typos and grammatical errors, e.g. in Abstract “uplift of pipeline under the combined action of earthquake and ocean wave and current loading” is better to be “earthquake, ocean wave and current loading”. Or “ can be expressed as follows”. and etc.

Response: As suggested, a detailed editing has been done through the manuscript by the authors, in order to correct grammatical errors and improve the readability of the manuscript. In particular, in Abstract “uplift of pipeline under the combined action of earthquake and ocean wave and current loading” has been revised as “earthquake, ocean wave and current loading” as suggested. The sentence “can be expressed as following” has been modified as “can be expressed as follows”.

COMMENT 3: benchmark data for validation part should be refereed and clarified.

Response:  The benchmark data for model validation has been refereed and clarified in Sect. 2.3 Indeed, the benchmark test has been performed using the automated hollow cylinder apparatus by the authors and published in Zhao et al. (2020). Please see the details in the Lines 118-126.

 

COMMENT 4: regarding the fig 3 maybe the necessity of this work is better to be highlighted in the introduction.  

Response: We appreciate the instructive comment. The Introduction has been extended by including the project backgrounds regarding the Fig. 3 as well as highlighting the necessity of this work. Please see the details in the Lines 58-70.

Reviewer 2 Report

Thank you for sending in your manuscript. It's an interesting topic, and you attempted to model it. When loosely packed, water-logged sediments at or near the ground surface lose their strength in response to strong ground shaking, liquefaction occurs. Liquefaction beneath the sub-marine setting and other structures may cause significant damage during earthquakes.

 

However, this work requires significant revision before it can be published online.

First and foremost, the manuscript's language is poor.  There are several grammatical mistakes. I got lost many times while reading the text to figure out what it meant.

 

Second, in the introduction section, you listed the accomplishments of several scholars who have worked in the same topic. However, I don't see any critical discussion sections, etc. I don't see any discussion part where your reported domain results are compared or justified. There are simply your results in section 4. Result and Discussion. Because this is a hot topic, you must connect it regionally with the published domain and show that your work should be taken into account in the oil and gas industry.

Author Response

Response: Thanks for sparing time to review the manuscript. We appreciate the positive comments. We have carefully addressed all the comments in this response as well as in the revised manuscript. Please note that all changes are marked red in the revised manuscript. The reference is also updated accordingly. Our responses are summarized as follows.

First and foremost, the manuscript's language is poor.  There are several grammatical mistakes. I got lost many times while reading the text to figure out what it meant.

Response: As suggested, a detailed editing has been done through the manuscript by the authors, in order to correct grammatical errors and improve the readability of the manuscript.

Second, in the introduction section, you listed the accomplishments of several scholars who have worked in the same topic. However, I don't see any critical discussion sections, etc. I don't see any discussion part where your reported domain results are compared or justified. There are simply your results in section 4. Result and Discussion. Because this is a hot topic, you must connect it regionally with the published domain and show that your work should be taken into account in the oil and gas industry.

Response: We appreciate the instructive comment. The critical discussion about the difference between our research and existed researches has been highlighted in Introduction. In particular, we have presented the innovation of this study explicitly in the Introduction. Please see the details in the Lines 49-54.

Furthermore, we have added and highlighted the practical engineering significance of the findings in the Results and Discussion section. Please see the details in the Lines 267-277.

Reviewer 3 Report

 

You investigated the impact of trench backfilling on the residual liquefaction around pipeline and the induced uplift of pipeline under the combined action of earthquake and ocean wave and current loading. It is an interesting topic. However, there are a number of issues with your current manuscript that need to be addressed before I can recommend acceptance of your paper:

1. Introduction: The innovation of this study should be presented clearly. I suggest the author reorganize this part to highlight the difference between your research and existed researches.

2. Line 67，σ_ij should be σ_sij.

3. Figure 2 shows that the calculated and measured excess pore water pressure curves with time are similar in distribution, but there are large gaps in their values at many locations, with the maximum difference being close to 20 kPa. Therefore, the authors say that "the prediction results of the method proposed in this paper are in good agreement with the laboratory test data" need to be carefully described, and the reason for the large difference should be given.

4. your literature review appears to be missing the work published in “Tunnelling and Underground Space Technology incorporating Trenchless Technology Research”, such as “Experimental and numerical study on polymer grouting pretreatment technology in void and corroded concrete pipes”.

5. What is the basis for the selection of grid size? Has a mesh sensitivity analysis been performed? The grid size of the pipeline is 0.1 m×0.1 m, and its thickness is only 0.2 m, such a grid size is obviously unreasonable. In addition, the grid of seabed soil is 1 m×1 m, how can such a large grid size ensure the calculation accuracy? This requires a careful explanation.

6. What is the basis for the selection of parameters in Table 2?

Author Response

Response: Thanks for sparing time to review the manuscript. We appreciate the positive comments. We have carefully addressed all the comments in this response as well as in the revised manuscript. Please note that all changes are marked red in the revised manuscript. The reference is also updated accordingly. Our responses are summarized as follows.

1. Introduction: The innovation of this study should be presented clearly. I suggest the author reorganize this part to highlight the difference between your research and existed researches.

Response:  As suggested, we present the innovation of this study explicitly in Introduction. In particular, the difference between your research and existed researches is highlighted. Please see the details in the Lines 51-56.

 

2. Line 67，σ_ij should be σ_sij.

Response: Revised as suggested.

 

3. Figure 2 shows that the calculated and measured excess pore water pressure curves with time are similar in distribution, but there are large gaps in their values at many locations, with the maximum difference being close to 20 kPa. Therefore, the authors say that "the prediction results of the method proposed in this paper are in good agreement with the laboratory test data" need to be carefully described, and the reason for the large difference should be given.

Response: We completely agree with the Reviewer. The statement "the prediction results of the method proposed in this paper are in good agreement with the laboratory test data" has been modified as “the prediction results of the method proposed in this paper are in relatively good agreement with the laboratory test data”. The proposed method is able to predict the overall trend of the development of excess pore water pressure of the soil element under bidirectional loading.

Furthermore, the difference between the prediction and testing data has also been discussed in the Lines 121-128.

 

4. your literature review appears to be missing the work published in “Tunnelling and Underground Space Technology incorporating Trenchless Technology Research”, such as “Experimental and numerical study on polymer grouting pretreatment technology in void and corroded concrete pipes”.

Response: We appreciate this comment. This important paper is instructive and cited in the manuscript.

 

5. What is the basis for the selection of grid size? Has a mesh sensitivity analysis been performed? The grid size of the pipeline is 0.1 m×0.1 m, and its thickness is only 0.2 m, such a grid size is obviously unreasonable. In addition, the grid of seabed soil is 1 m×1 m, how can such a large grid size ensure the calculation accuracy? This requires a careful explanation.

Response: Indeed, it is a complex task to determine an appropriate grid size for an explicit time matching finite difference analysis of dynamic soil-structure interaction, as it depends on many factors. In particular, the major concern of this study is the seabed liquefaction simulation around a pipeline and the induced uplift of pipeline. The deformation and internal force of pipeline is of secondary importance. For this reason, only two elements have been set along the thickness of pipeline. Mesh sensitivity has been performed carefully before the analysis to achieve the balance of computational efficiency and accuracy.

The statement is added in the Lines 149-150.

 

6. What is the basis for the selection of parameters in Table 2?

Response: The assumed soil parameters are calibrated from the shear stiffness and damping ratio curves of natural marine sediments from a typical borehole at the Bohai Strait.

The statement has been added in Line 154-156.

Round 2

Reviewer 1 Report

please add recent relevant references

Author Response

Comments and Suggestions for Authors: please add recent relevant references

Response: Thanks for sparing time to review the manuscript. We appreciate the positive comments. As suggested by the Reviewer, recent relevant references have been added as appropriate.

Reviewer 2 Report

Now that the most of my comments have been addressed, the manuscript is in much better shape. However, if the authors could concentrate more on the discussion section, the paper would be improved. Since I am unable to locate the discussion section et al. In Section 4, simply the results are reported, with no indication of discussion and so on.

If no discussion occurs, the significance of this article will be limited to a purely local level. It cannot be of regional or international significance. In the introduction, the authors have previously cited a number of previous works. This work is not a unique contribution that cannot be validated against the published domain.

Author Response

Comments and Suggestions for Authors: Now that the most of my comments have been addressed, the manuscript is in much better shape. However, if the authors could concentrate more on the discussion section, the paper would be improved. Since I am unable to locate the discussion section et al. In Section 4, simply the results are reported, with no indication of discussion and so on.

If no discussion occurs, the significance of this article will be limited to a purely local level. It cannot be of regional or international significance. In the introduction, the authors have previously cited a number of previous works. This work is not a unique contribution that cannot be validated against the published domain.

Response: Thanks for sparing time to review the manuscript. We appreciate the positive comments. As suggested by the Reviewer, special discussion on the analysis results have been added and the practical engineering significance of the key findings in this study has also been highlighted. Please see the details in Lines 277-281.