Behaviour Analysis of Reinforced Soil Retaining Wall According to Laboratory Scale Test

Round 1

Reviewer 1 Report

1) ARTICLE SUMMARY

 

In the paper, the influence of the shape (convex or concave) and of the angle (60°, 90°, 120° and 150°) of the curved portion of reinforced earth retaining walls on the behaviour of the wall is assessed. Specifically, in the paper the results of laboratory (indoor) tests performed at 1 g on different reduced-scale earth retaining walls are shown. As expected, greater (outward) displacements are observed in the convex walls, particularly in the presence of small values of the angle defining the curved portion at hand.

The paper can be roughly divided into four parts. After a brief review of the literature (§ 2), the methodology adopted to detect the results of the research is outlined (§ 3). The results of the laboratory tests are then presented and discussed (§ 4), followed by conclusions (§ 5).

 

2) COMMENTS AND REMARKS

 

Although the strengths of the paper are clarity in pointing out the flaws and lacks of existing design procedures, in detecting the effect of the shape and of the angle on the displacements experienced by the curved portion of the wall, and in discussing the obtained results thoroughly, there are several weaknesses. First, a limited state-of-the-art review is given. Then, the key parameters defining the curved portion of the wall (i.e. the angle) and the mechanical properties of the sand used in the laboratory tests are not defined nor sketched (as far as the angle is concerned). Besides, the methodology used in performing the laboratory tests is not given, while objectives of the research are not clear: as an example, the vague words “displacement characteristics” are used throughout the paper without specifying if either the amount or the direction (or both) of the displacements are the main concern of the paper. Besides, the obtained results are just reported without giving the reader any physical interpretation or comment on the observed behaviour of the walls. Analogously, design implications of the discussed results are not provided, whereas they could have been useful to the readers of the journal. Finally, Figures and References provided in the paper are not properly recalled in the text, and a low-level English language and style is adopted.

Major and minor issues are listed below for each paragraph of the paper.

 

2a) Major issues

 

In the Abstract:

p. 1 lines 32-36: when indicating the sections of the curved portion as a function of the D the phrase is not clear, as a Figure would be needed. Please try to clarify; p. 1 line 37: the terms “curvilinear design presentation” are not clear. Please explain better.

 

In the Introduction:

p. 2 line 53: when recalled in the text, references should be numbered consecutively, following the order in which they are cited (e.g. Lee et al. should be numbered as [1], not as [5]). This requirement should be met throughout the paper. Please modify; p. 2 line 58: the terms “displacement characteristics” are massively used throughout the paper. Are the Authors thinking about the module or direction (or both) of the displacement vectors? Please be more specific; p. 2 lines 59-60: Authors state: “At present, the design of reinforced soil retaining walls is carried out through limit equilibrium analyses…”. First, some references supporting this statement are needed (see Cai and Bathurst, 1996; Huang et al., 2003; Baker and Klein 2004 a and b). Second, this is not entirely true, as the Limit Analysis is widely adopted for the design of reinforced retaining walls, both under static and seismic loadings (Michalowski, 1998; Gaudio et al. 2018). Please add all these references to widen the Introduction and Literature Review; p. 2 lines 60-62: the statement “These have a limit that the behaviour characteristics of the curved portions of reinforced soil retaining walls that are constructed in the actual field Jung et al. [3].” Is meaningless. Perhaps a verb is missing: please amend; p. 2 lines 62-63: the Authors state: “…the curved part of a reinforced soil retaining wall was copied through an indoor model experiment…”. What does “copied” stand for? Please replace using “reproduced”.

 

As far as the second paragraph (“Literature review”) is concerned, the following remarks can be made:

p. 2 § 2.1: more details related to the mentioned walls should be given (e.g. location of the wall, mechanical properties of both the reinforced soil and reinforcements); p. 2 line 78: Authors state: “…at about 80 m.”. But from what? Please clarify; p. 2 lines 84-85: the phrase “Sufficient study at the time of design and precise work according to the regulations at the time of construction are required.” Is not clear. Please modify; p. 3 lines 97-98: “…safety factors such as activity and falls.”. The meaning of this phrase is not clear: please amend; p. 4 lines 107-108: the statement: “the behaviour characteristics of the reinforced soil retaining wall due to overburden load.” is not totally clear. It could be amended as it follows: “A model test was conducted to analyse the influence of the overburden load on the behaviour of the reinforced soil retaining wall.”; p. 4 line 110: then what is the main contribution by Wong et al.? p. 4 line 111: what kind of model experiment did Ki et al. conduct? Please provide more details to improve the Literature Review; p. 5 line 124: instead of using the formula “according to” it could be useful to adopt the following sentence: “Lee et al. compared the behaviour of curved and straight sections varying the shape of a reinforced soil retaining wall…”; p. 5 lines 124-128: all the Figures presented in the paper are to be recalled in the text. As an example, Authors did it for Figure 5, but they did not for Figure 6 and others in the paper. Please edit; p. 6 line 131: the words “behaviour characteristics” could be replaced by the shorter “behaviour” throughout the paper. Please amend.

 

In the third paragraph (“Laboratory model test”):

p. 7 lines 152-153: Authors state: “The reinforcement used a reinforcing material in the indoor model.”. This vague sentence does not provide any additional information. Please add more details about the reinforcing material; p. 8 lines 162-167: more details about the soil used in the backfill ground should be provided (e.g. angle of shearing resistance); p. 8 lines 171-172: after reading this phrase it is not clear what is the adopted relative density D_R of the sand. Please clarify; p. 9 line 175: the meaning of the statement “A total of eight room model experiments were conducted by partitioning” is not clear. Perhaps some words are missing: please amend; p. 9 line 185: perhaps the words “…with respect to…” could be added between “construction” and “than”.

 

In the fourth paragraph (“Results”):

p. 10 line 189: title “According to angle” is not correct in English. Please modify in “Influence of angle of the curved portion” (and the same for the title of § 4.2); p. 10 line 191: in Figure 13(a) the deformed shapes of the wall are showed, not the displacements (indeed the title of the y-axis is “Height” and not “displacement”). Please modify; p. 10 line 199: when defining the angle, a sketch is needed. Please add a sketch Figure; p. 10 line 204: the arching effect is just mentioned here, while this represents the main physical reason of the results of the paper. Please elaborate on this statement; p. 11 Fig. 14, p. 12 Fig. 15: the walls considered in the tests are 1-m high (as given at page 4, line 107), so why do the data stop at 600 mm (y-axes)? p. 11 Fig. 14: some walls experience up to 400 mm displacement, corresponding to 4%D. Perhaps the walls are reaching limit conditions or collapse? Which are the values of the safety factors of the considered walls? Are they equal for all the walls, that is are the walls characterised by the same shear strength mobilisation?

 

In the fifth paragraph (“Conclusions”):

§ 5: given conclusions just report the already discussed results, whereas they are meant to provide the reader with some physical reasons behind the observed phenomena and with some design suggestion, otherwise conclusions are just repeating the same things discussed in the previous paragraphs. Please modify.

 

In the References:

References: some references do not provide with the journal, volume number, issue number, pages (e.g. see Kim et al.). Please add all the relevant data.

 

2b) Minor issues

 

In the Abstract:

p. 1 line 18: maybe a term better than “tongue” could be adopted. Please modify; p. 1 line 26: “but” should begin with the capital letter “B”. Please edit.

 

In the second paragraph (“Literature review”):

p. 4 line 111: acronym “LVDT” = Linear Variable Differential Transducer should be written in full in the first place; p. 5 line 122: please use “to reproduce” instead of “to copying”.

 

3) CONCLUSIONS

 

Based on previous comments and remarks it can be concluded that the paper presents an interesting study characterised by some strengths and several weaknesses, the latter mainly regarding the systematic introduction of the input and output parameters defining the problem at hand and the interpretation of the obtained results that could have shed some lights on the behaviour of retaining walls presenting curved parts.

In conclusion, based on the previous observations and comments, it is my opinion that the paper can be reconsidered for publication in Applied Sciences after major revision.

 

4) REFERENCES

 

Cai, Z. Bathurst, R. (1996), “Seismic-induced permanent displacement of geosynthetic reinforced segmental retaining walls”, Canadian Geotechnical Journal, Vol. 33, No. 6, pp. 937-955. Huang, C., Chou, L., Tatsuoka, F. (2003), “Seismic displacement of geosynthetic-reinforced soil modular block walls”, Geosynthetics International, Vol. 10, No. 1, pp. 2-23. Baker, R., Klein, Y. (2004a), “An integrated limiting equilibrium approach for design of reinforced soil retaining structures: Part I – formulation”, Geotextiles and Geomembranes, Vol. 22, No. 3, pp. 119-150. Baker, R., Klein, Y. (2004b), “An integrated limiting equilibrium approach for design of reinforced soil retaining structures: Part II – design examples”, Geotextiles and Geomembranes, Vol. 22, No. 3, pp. 151-177. Michalowski, R.L. (1998), “Limit analysis in stability calculations of reinforced soil structures”, Vol. 16, No. 6, pp. 311-331. Gaudio, D., Masini, L., Rampello, S. (2018), “A performance-based approach to design reinforced-earth retaining walls”, Vol. 46, No. 4, pp. 470-485.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Summary: The authors constructed indoor room-scaled model to study the behaviour of reinforced soil retaining wall. Comments: 1. There are quite a few typing error or not completed sentences which makes it hard to understand the context. Please proof read before submission. i.e. Line 26, 'but the research on it is also a few facts', Line 171, 'ensure aim of relative density, it was ...' Line 180 ' positions. Smith et al [14] This information was' 2. Line 193-195, D and H are the same. More notation is making the reader hard to understand the context. Do keep them consistent. 3. References are not in sequence in the text. Please sort them start from [1], [2], etc. 4. In section 3.1, the geometry are not fully labelled. This can be hard to others to repeat the same experiment. i.e. What is the thickness of each layer? Distance between Geogrid? What is the geometry of geogrid? What is the distance between each 'dot' in Figure 7? Did the authors follow the set up as mentioned in literature review in Section 2.3? This are not mentioned clearly in the text. 5. Table 1, What are No. 1, 2, 3,4 and 5 exactly? Type of soil? how about other properties (mechanical properties)? Sources? 6. Line 149-150, Are they 50 kN/m and 0.23 kN/m ? 7. Line 151, why choose No 5? the value is still consider high by comparing 3.4 kN/m to 0.23 kN/m. Can the authors justify on the use of type of reinforced material? 8. Figure 8. "R"einforced .... 9. Can the authors label Figure 10? From reader's point of view, it just looks like a crane is hanging some rectangular box. 10. Figure 11 is not describe in the text. What is the sequence diagram related to? 11. The height (y-axis) used in Figure 13,14,15,17 and 18. Is the height measured from top to bottom or bottom to top? It is not clear and not mentioned in the text. 12. Reviewer have not clue what define the x-axis for Figure 13, 14, 15 with Distance measured in term of D. -1.5D, -1D, -0.5D, ..... 1.5D. Can they be define in Figure 7? or draw a schematic drawing to label them? 13. Lots of results are plotted and described. However, there is no explanation or discussion on the results. What does it mean by larger horizontal displacement? How many experiments have been repeated? How reliable is the results? What is the errors? 14. The reviewer cannot conclude anything from presented work. How will this work contribute to the field scenario? Include the finding into design criteria? 15. Can the authors draws any relationship between convex design and concave design with different angles?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Authors correctly amended the paper following Reviewer's comments. However, some minor issues have been still detected, as reported in the following.

Referring to the list presented in the cover letter provided with by the Authors:

 

5) it is Reviewer's opinion that 13 out of 16 (i.e. 81%) of references to Korean papers is a non-acceptable amount in a paper to be published in an international Journal, as Applied Sciences is. That is the reason behind the suggestion given in the first review, when some well-known papers published in the same topic in international journals were given, as they can be of interest for the readers of Applied Sciences;

 

16) Figure 8 is still not recalled in the text. Please amend;

 

33) a misprint is detected: please modify in "Linear Variable Differential TransducerS".

 

CONCLUSIONS

 

Based on previous minor issues, it can be concluded that the paper is clearly improved. Therefore, it could be accepted after amending he minor issues here reported, mainly related to the Introduction paragraph.

Author Response

Thank you for the kind and helpful comments on the paper. We have responded to the comments as follows.

it is Reviewer's opinion that 13 out of 16 (i.e. 81%) of references to Korean papers is a non-acceptable amount in a paper to be published in an international Journal, as Applied Sciences is. That is the reason behind the suggestion given in the first review, when some well-known papers published in the same topic in international journals were given, as they can be of interest for the readers of Applied Sciences;

☞ Based on the reviewer's comment, the authors added the following sentences in the manuscript. (p. 4 line 115).

The Federal Highway Administration (FHWA, 2009) [8], the National Highway Administration (AASHTO, 2012) [9] and the North American Association of Concrete Stones (NCMA, 2016) are referred as representative geosynthetics reinforced soil wall design method applied to the oversea construction.

According to FHWA (2009), it is mentioned regarding an acute part of GRS wall that “wall angle points with an interior angle of less than 150 degrees shall be considered to be a wall corner. the wall corner shall provide a positive connection between the sections of the wall on each side of the corner such that the wall backfill material cannot spill out through the corner at any time during the design life of the wall.”

In the AASHTO (2012), it is noted with respect to definition of curved prat of the GRS wall “The curved part is defined as the intersection of the two walls at or below 120 degrees.” and that is need and applied to domestic design manual.

NCMA (2016) has state regarding how to set reinforced material at the curved part that “When the gaps between adjacent geogrid exceed 20 degrees, place additional reinforcement on next course of segmental units immediately above the specified placement elevation, in a manner that eliminates gaps left by previous layer of geosynthetic. Repeat for subsequent courses where geogrid is specified to be located.”

 

Figure 8 is still not recalled in the text. Please amend

 

 ☞ Figure 8 was revised following reviewer’s comment. If you don’t have satisfied this correction, the authors will appreciate that let the authors know which figure is suitable. The authors will be willing to correct again following your second comment (p. 8 line 200).

 

a misprint is detected: please modify in "Linear Variable Differential TransducerS".

 

 ☞ “Linear Variable Differential” is modified to “Linear Variable Differentials” depending on reviewer’s comment. (p.5 line 145).

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors have addressed the recommendations and suggestions appropriately. The readability of the manuscripts has significantly improved. It would be recommended to publish the work after the final touch up.

Author Response

Thank you for the kind and helpful comments on the paper. We have responded to the comments as follows.

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

Authors correctly amended the paper following Reviewer's comments. However, the last minor issue has been still detected, as reported in the following.

Referring to the list presented in the last cover letter provided with by the Authors:

2) Figure 8 is still not recalled in the text. With "recalled" the Reviewer means that the Figure is not directly mentioned in the main text (e.g. "In Figure 8 the reinforcing material tensile strength test is depicted..."), and not that the Figure itself should have been changed. Please amend;

Author Response

Thank you for the kind and helpful comments on the paper. We have responded to the comments as follows.

Figure 8 is still not recalled in the text. With "recalled" the Reviewer means that the Figure is not directly mentioned in the main text (e.g. "In Figure 8 the reinforcing material tensile strength test is depicted..."), and not that the Figure itself should have been changed. Please amend;

☞ The following sentence was added in accordance with the reviewer’s comments   "Figure 8. shows the reinforcement used in the indoor model experiment.” (line. 199 ,page. 8)

Author Response File: Author Response.pdf