Experimental Investigation of the Dynamic Behavior of Submerged Floating Tunnels under Regular Wave Conditions
Round 1
Reviewer 1 Report
Interesting paper, but rather limited in elaboration. Do you expect problems with the fact that you only did use regular waves? And I see problems with your conclusions due to the fact that the stiffness is not scaled correctly in the physical model. The parameter you use to describe the process (H/L) seems to be not a very good one.
Detailed comments:
31: So, SFT has become one of the most... Please add "potentially" after become. It has not been applied in real tunnels yet.
63: explain what is BWR
65: Your literature overview is much focused on Chinese literature. It might be good to include also research from other parts of the world, to prevent you have a problem with "tunnel vision". When I type "Archimedes bridge submerged floating tunnel" in Google Scholar I find many papers from outside China.
88: "The important progress has been achieved." This is no English sentence.
100: You use Froude scaling, which is OK for the hydrodynamics, but certainly not for the turbulence and the dynamic behaviour of the structure. The stiffness of your structure and the anchor cables are certainly not on scale 1:60.
117: Regular waves are used. 1) Is this sufficiently accurate? 2) Regular waves in a basin are notorious for reflection effects of the basin boundaries. How did you deal with this?
144: In this section I expect to find info on the scaling of the elasticity of the mooring cables as well as on the stiffness of the tube and the connections.
184: It is recommended also to make a sketch on scale, indicating dimensions of the tunnel, depth and submergence depth of the tunnel
205: Table is not very clear. are for the Reliability Test 4 test done (so H=0.06 and T=0,86,..) or 16 tests (including H=0.06 and T=1.1). It is not logical to mention in column2 H and T, and in column3 T and H.
279: Basically this is wave steepness. Why not using the internationally more common s=H/L. And is indeed the local wave length so relevant? Or is it the period; then s0=H/L0 might be a better parameter. In your test (d=2.2 m) it is deep water, so L=L0.
297: This figure needs more discussion. I assume you see the sets with T=0.8 T=0.9 and T=1.0 s. So your parameter H/L not a very good predictor.
345: I cannot conclude this from your figure 8. The only thing I conclude from fig 8 is that the range of wave pressures is constant as function of steepness.
372: Because you use in these figures only dashed lines, they are difficult to read.
Author Response
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Author Response.pdf
Reviewer 2 Report
This paper discusses the behavior of submerged floating tunnel under wave action and pressures, cable forces based on the hydraulic model experiments. Results are very significant and are of interest.
Before its publication, however, there are some comments on this paper and I would like to suggest the authors to consider these comments in the attached file.
Comments for author File: Comments.pdf
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
The article suffers of significative lacks in the description of the work. Several comments and suggestions are reported hereinafter to produce a clearer document. And a more comprehensive revision of the manuscript if post-postponed after a major revision, in due course.
It is said in the introduction: “So, SFT has become one of the most competitive cross-sea constructions in the twenty-first century”. Can it be proved based on existing literature? Cite the related references if any. On the contrary, add a sentence such as “…. the authors believe that ….”. Note that, in the following sentence it is also reported that “… Although the concept of SFT has been proposed for a long time, the actual engineering of SFT has not been implemented due to safety and stability issues caused by various environmental loading excitations …” and it seems to contradict of the first sentence. Authors are requested to clarify this point.
Correct the typo in the sentence: “…Reliability verified by physical model in wave flume. Mai carried out a study on the …”
Line 49: “ … CR columnar …” define CR
Line 63: “… The BWR of the tube body played …” define BWR
Figure 1: It would be clearer if a schematic layout of the flume and its components was depicted instead assembling pictures.
Line 136: “ ... BWR of this test is designed as 1.3 …” it would be appreciated by the readers if also the model total weight was provided.
Line 138: “ … thickness of the model …”. Do the authors mean: the thickness of the acrylic material used for model construction?
Line 139: “… the model material is acrylic model … ”, change in “the model material is acrylic”
Line: 137: it is said that “… The long and short axes of the model are made according to 0.75 m × 0.317 m …”. Are these values related to the cross section elliptical shape's axes? If yes, what is the length of the SFT segment? Authors are requested to clarify this point.
Line 156: add full scale range and accuracy of the pressure sensors (possibly model and producer)
Line 161: “ … T the tension sensor can measure the cable forces. ..”. If it is a tension sensor how can it provide a force measurement? The authors also provided “ … . Its maximum range of 20 KPa …”. Are the units really KPa? It seems to this reviewer a force sensor. Clarify this point and preferably report the force full scale range (KN) and accuracy of this sensor. Note that in the figure 9 forces are depicted in the Y axis.
Line 165: “ … The numbers of the cables are named C1–C8, and C1–C4 and C5–C8 are respectively 165 arranged at both ends of the model …”. Depict this arrangement in a schematic layout.
Line 172: “… The anchor cable passes through the pulley and is connected with the tension sensor by clamping with stainless steel collet …”. I would suggest using the term "mooring cable" instead of "anchor cable".
The use of pulleys to conduct measurements of forces acting on the mooring cables may be source large inaccuracy. Authors are requested to provide evidence of the expected accuracy in the measurements of mooring forces in dynamic conditions.
Line 203: “ .. The wave propagation direction is always perpendicular to the SFT model cross section. …” Do the authors mean “model longitudinal section”? Add a schematic layout where the transversal/cross and the longitudinal directions are clearly depicted.
Line 206: “ .. 3. Reliability verification for wave loading …”. This reviewer believes that the rational of comparing experimental measurements with “theoretical solution” is questionable. What theoretical solution? There are many different theories, e.g. first order, second order. In any case, all theories are developed under the assumption of hypothesis that are, in principle, not realistic and as such the experimental modelling is much accurate that the so called “theoretical results”. Stated in different form, the experimental modelling can prove the validity of a theory and not the contrary! So, I think these tests can only be useful to figure out if regular waves have been effectively generated and to provide measurement of effective wave height under which the model has been tested. As such this paragraph must be totally rewritten.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Paper is much clearer. The main point I still have is the scaling of the forces. You have scaled down the tension cables also with a factor 60, but then they are relatively too stiff. Qualitatively your conclusions remain the same, but quantitatively you may have a problem, especially when discussing the dynamic response. Some comments in the paper is necessary.
Small comment: In the new 3d graphs (6, 10, 11) is put H/L on one horizontal axis, and nothing on the other. I assume on the other axis one should read H. Is this he case?
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
I think the authors adquately revised the paper. If possible, variations in Figure 4 and Figure5 are changed to solid lines.
Author Response
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Author Response File: Author Response.docx
