Deformation Response of a Pipeline to Nearby Deep Foundation Pit Excavation: Numerical Simulations and Field Tests

Round 1

Reviewer 1 Report

Through both field measurements and numerical method, this paper studied the deformation response of an existing pipeline to the deep foundation pit excavation of nearby soil. Parametric study on the distance between the foundation pit and pipeline, construction methods of foundation pit excavation, as well as soil properties are carried out to learn the deformation response of pipeline. This study is interesting and is significant to the optimization of operation policies of foundation pit excavation of area where buried pipeline exists. However, there are some problems in the present paper. The comments that should be addressed are listed as follows:

1. Lines 59-61, this citation is improperly since it is irrelevant to the study of this paper.

2. In lines 132-135, the second and third steel supports in the project were respectively implemented with 50 kN and 100 kN prestress. Did this prestress also be implemented on the steel supports in the numerical simulation? If not, does it have great impact on the accuracy of the results?

3. In lines 182-183, what is the meaning of “m”, there is no “m” in equation (1)?

4. Lines 192-193, it would be better to add something in figure 5 to denote the outward extended 50 m distance of the model to make it more understandable for readers.

5. Lines 225-226, this sentence needs to be rewritten, since it is difficult to understand what the author wants to interpret.         

6. Lines 253-255, where did the results of the variation in horizontal displacement at points 2 and 3 come from? Please add an expound to clarify it.

7. In lines 71-76, the author said to consider the soil-pipeline interaction as full contact is not proper, which means in this study the interaction between soil and pipeline did not apply this method in the numerical simulation, please add an expound on how the soil-pipeline interaction was considered in this paper?

8. Figure 12, the words “Gap width” on this figure displayed poor quality, please fix this problem.

9. Lines 398-399, refers to comment 5.

10. Lines 516-517, the expression “Poisson’s ratio improves the deformation capacity of soil and enhances the disturbance of soil excavation” is improper, the author may want to interpret that the deformation capacity of soil with greater Poisson’s ratio is greater and more sensitive to the disturbance from excavation. Please rewrite this sentence in a proper expression.

The overall quality of English writing is OK, minor editing is required.

Author Response

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Reviewer 2 Report

The authors explore the impact of DFPE on an adjacent oil pipeline by numerical simulation and 11 field testing methods. Based on the project of Xinxingcun Station of Tianjin Metro Line via two approaches of layered excavation and bench excavation.

The work looks worthy for publishing, however, the authors need to address the following:

1. The finite element method based on the continuous medium model is adopted in the current work. however, the modeling equations (they are of the form of partial differential equations) should be explained and stated. This point is import for readers as they may need to generate similar results for similar work.

2, The authors must indicate in the introduction section that spectral element method can be utilized due to its accuracy when compared with the finite element method. They should refer to Persistence of photonic nanojet formation under the deformation of circular boundary,      and On-and off-optical-resonance dynamics of dielectric microcylinders under plane wave illumination. Both articles were published in Journal of the Optical Society of America B.

3. The authors should discuss and explain the choice of elements sizes regarding figure 5. Based on what such mesh was decided? ! are all elements of same size? 

4. More explanations are required regarding the huge discrepancy between bench and laminar excavation results are required.

 

 

Minor typos

Author Response

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Reviewer 3 Report

Basic remarks

How the  elastic modulus described on the text and presented in tables 1 and 3 was determined?  The result of geological measurement (presented in fig. 2) does not include the elastic modulus.

On what basis the registering points 1, 2 and 3 (presented in figure 6)  were chosen. Why this points were not localized at other places of the model? Most relevant from the pipeline point of view  is registering the deformation of the soil  in vicinity of pipeline.

Table 1. Please add the source of friction coefficient included in table 1. Why the friction coefficient for DN200 pipe equals 0.3? All data included in the tables, which were not determined by the authors, should refer to references/sources.

Additionally, why the friction coefficient (in table 1) is different for silty clay? The friction coefficient between two body /material does not depend on its thickness.

Remark to figure 11a). It can be seen, that the pipe penetrates the soil? Does it mean the model lost the contact between two bodies?

Paragraph. 3.3.

How the authors simulated the excavation stages. The volumes of the soil was progressively removed from the model? Please provide the more accurate description of the numerical model especially how to simulate the excavation stages.

The basic question to this paragraph is: why the measuring the gap distance between the pipeline and soil was taken as a criterium to assess a safety of the pipeline? The most relevant way is register the stress (e.g. equivalent von Misses) and basis on this, the safety of the pipeline can be assess. The displacement can be used additionally, to verified the numerical model, but it shouldn’t be the criterium of assessment  of the safety. How to prove, that the lateral displacement of the pipeline e.g.  12 mm caused by bench excavation is a dangerous from the pipeline safety point of view?

 

Other remarks

Page 4 line 126 what means the “@” mark?

Authors use alternatively the “laminar excavation” and “layered excavation”, Please uniform the name. More proper is using layered excavation. Laminar excavation exist,  among others, in Fig. 7 and 8.

Figure 8 and 9 should be split out.

Figure 16 includes three chart. They should be marked as a a), b) and c) and captioned.

Author Response

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Reviewer 4 Report

1.      Split the second paragraph of the introduction.

2.      Discuss the model validation in details.

3.      Concise the conclusion part.

4.      Enrich the literature with international authors findings/research/articles.

Minor editing required. 

Author Response

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Reviewer 5 Report

This paper aims to explore the impact of DFPE on an adjacent oil pipeline by numerical simulation and field testing methods. The authors have generally performed a good job. However, there are some comments that need to be addressed.

11.  In line 192: Based on the experience of whom? Please provide reference

22. How is the size of the model selected? Was there a sensitivity study on the dimensions of the model?

33.  I recommend discussing the pipeline settlement shown in Fig 19 based on soil type also.

44.  The authors need to explicitly recommend when to use bench excavation and when to use layered.

Minor English changes are required.

Author Response

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Round 2

Reviewer 3 Report

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