Analysis of the Working Performance of a Back-to-Back Geosynthetic-Reinforced Soil Wall

Round 1

Reviewer 1 Report

General comment:

The changes introduced in the paper significantly supplement its content.

However, it is advisable to implement the corrections listed below 

Detailed comments:

- line 22-23: is “…displacement and settlement…” should be ““…lateral displacement and settlement…”

- the deformation moduli shown in Table 4 require units

Reviewer 2 Report

Dear authors,

I congratulate you for the work. I understand that the article is well presented. Objectives are clear and methods well presented. The conclusions corroborate the objectives and the citations from the literature clearly emphasize the context of the work. 

I believe the article can be accepted in the format in which it is found. 

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

General comment:

The paper presents analysis of performance of the construction of two separate walls with geosynthetics-reinforced soil in narrow spaces for railways. From an engineering point of view the field tests of the retaining walls included field measurements of the vertical and lateral pressures and geosynthetic strain presented in the paper are very important. The FEM analysis allowed to assess the influence of the length and arrangement of geosynthetics on post-construction deformation.

In order to improve the readability of the Figures with the results of measurements and calculations, it is advisable to use also different colors.

It is advisable to use the same references to Figures, for example Figure 15.

Detailed comments:

- line 92-93: “…Cement Fly-ash Gravel (CFG) pile composite foundation, the pile diameter is 0.4 meters, square arranged, and the pile length is 4.0 meters. …”. Nowadays, when rigid inclusions are used, the name “columns” are used instead of “piles”.

- line 114: “… trial test …”. What is this test? Is it triaxial test ?

- line 115: “…Standard proctor…”. Proctor is the name of the engineer who introduced this test into practice, so use a capital letter “Standard Proctor”.

- Figure 4: Curve of particle size distribution is most often shown with particle size values of the X axis increasing from 0.001 to 100 mm.

- Figure 5: “Trial” “Trial test”. What is this test?

- Figure 6: Figure caption should be corrected: Post-construction deformation of the left blocks and right panel over time.

- Figure 7: the Figure 7b is not correct and must be replaced. The Figure captions 7a, 7b and 7 must be changed.

- line 214-215: For walls having 5.0 m to 8.0 m long-geogrid, the maximum post-construction settlement on the top is 138.12 mm, 73.67 mm, 47.86 mm and 34.30 mm, respectively.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The paper investigates the effects of the reinforcement length and arrangement on back-to-back geosynthetics-reinforced soil walls (BBGRSW). Parametric FEM analysis was carried out based on a monitored structure located in the Qing-Yan-Wei-Rong Intercity Railway, Shandong Province, China. The study aims to evaluate the impact of those factors on the settlements at the top, facing lateral movements, tension in the reinforcements and factor of safety, including the post-construction behavior with time of the BBGRSW. Nevertheless, the uniaxial geogrid was simulated as a linear elastic material and the rheological behaviour was not taken into consideration in the analyses. Additionally, the interaction between the block-backfill, block-block and foundation-block were not properly simulated. Additional details are required regarding the constitutive model and the parameters used to simulate backfill behaviour. Moreover, some of the conclusions present in the paper depend on several other non-evaluated factors (eg.: external loading; soil compaction; type and stiffness of soil, facing and reinforcement) and cannot be generalized. The English is poor and should be revised by a native speaker. All in all, the reviewer does not recommend the paper for possible publication as a research paper in Applied Sciences Journal (Specific comments are founded 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 manuscript reports some results from an experimental (field) study and subsequent numerical simulation of the post-construction behaviour of a back-to-back geosynthetic-reinforced soil wall (BBGRSW). The numerical modelling was performed using the 2D finite-element software Plaxis. A parametric study was then conducted to investigate the influence of geogrid length and arrangement on the BBGRSW performance.  

The topic of the study is interesting and meaningful. However, the paper is generally difficult to follow and many clarifications are needed. In the Reviewer’s opinion, the paper can be published if the following comments can be successfully addressed.

Specific comments are listed below:

• Abstract: The abstract is currently too short and could be extended to about 200 words. I suggest the authors improve the Abstract by including additional information on the background/motivation of this study and on the methodology used. The main purpose of this study should also be clearly indicated. The sentence in lines 19-20 is not clear and should be rewritten.

• Introduction: The literature review should be improved. There are currently more studies on back-to-back geosynthetic-reinforced soil walls than those mentioned in this paper. Recent studies such as those listed below (among others) should also be reviewed and cited:

- “Numerical Study of the Behavior of Back-to-Back Mechanically Stabilized Earth Walls”. Geotechnics (MDPI). 2021.

- “Earthquake Response of Connected and Unconnected Back-to-Back Geosynthetic-Reinforced Soil Walls”. International Journal of Geomechanics. 2021

- “Effect of Reinforcement Stiffness on the Response of Back-to-Back MSE Wall upon Infiltration”. Geosynthetics International. 2021

- “Numerical evaluation of the performance of back-to-back MSE walls with hybrid select-marginal fill zones”. Transportation Geotechnics. 2021

- “Analysis of Single and Back-to-Back Reinforced Retaining Walls with Full-Length Panel Facia”. Geotechnical and Geological Engineering. 2020

• Lines 86-88: Instead of giving the commercial name of the geogrids (TGDG EG130R and EG170R), please provide the relevant geogrid properties including the aperture size and shape, so that readers can have an idea about the characteristics of the geogrids used. Please indicate either in the text or in Figure 2 where each different geogrid type was employed.

• Lines 99-101, Table 1 and Figure 2: The details of the instrumentation provided in the text (lines 99-101) do not seem to be fully consistent with those shown in Table 1 and Figure 2. Text: “the base pressure, the lateral earth pressure, the vertical pressure and the geogrid strain” and “inclinometers, earth pressure cells and strain gauges”. Table 1 and Figure 2: “Earth Pressure Cell; Strain Gauge; Settlement Meter; Displacement Meter”. Please revise.

• The characterisation of materials (filling soil and geogrids) as obtained by laboratory tests should be provided in a dedicated sub-section, rather than in the numerical model section (currently, Section 2.2). I suggest adding a new subsection (e.g. 2.2. Characterisation of materials) to describe the laboratory tests and the associated results. The next sub-section “Numerical modeling” should focus on the numerical modeling and associated input parameters.

• Table 3: The characterisation of the geogrid is very insufficient. Please provide additional properties, such as the mass per unit area, aperture size, thickness and percent open area. Also, please explain why two different geogrids were used in the field (TGDG EG130R and EG170R) and only one geogrid was simulated in the numerical model. Which one was tested in the laboratory and then simulated in Plaxis software?

• Table 4 should also indicate the constitutive model and input parameters used to simulate the filling soil in Plaxis (currently only the input parameters for the foundation materials are given).

• The authors should elaborate more on how the long-term post-construction behaviour of the wall was simulated in the numerical model. For instance, was the HDPE geogrid creep behaviour simulated numerically?

• Section 3.2: Please indicate the reinforcement type, arrangement, and vertical spacing between reinforcement layers considered in the parametric study of the geogrid length.

• Figure 11b: Why is the post-construction settlement at the embankment top increasing towards the right hand side of the BBGRSW when the reinforcement length is equal to 6m? For all other reinforcement lengths, the settlement does not significantly change with the distance to the embankment center.

• Section 3.3: Please specify the geogrid type and the vertical spacing between reinforcement layers considered in the parametric study of the geogrid arrangement.

• Lines 257-258: This sentence is not clear. It is mentioned that the cross-arranged reinforcement performs better than the same-layered reinforcement but the deformations in the former case were higher??

Minor editorial comments:

• Lines 34, 72, 78, 219, 248, etc.: Replace “GRS wall” with GRSW for consistency.
• Heading 3: “Results and discussion”. Heading 4: “Discussion and conclusions”. The discussion should be included either in section 3 or in section 4, not in both sections.
• Figure 2: The resolution of this figure must be improved. It is extremely hard to distinguish the different instruments installed within the wall. In addition, legends can hardly be read.
• Line 114: I believe there is a typo in “trial” and the authors meant “triaxial”. The same applies for Fig. 5 legend and caption. Please revise.
• Line 120: What do you mean by “was used to fit the soil”? Please rewrite. Also, replace “has been shown” with “is shown”.
• Lines 127: I believe “filling soil” should be replaced with “foundation soil” because Table 4 shows the input parameters of the foundation soil.
• Line 138: delete “was”.
• Figures 6-7, 9, 11 and 13 should be enlarged for better clarity. In Figure 6b, the measured results cannot be seen. Fig. 7 is not showing the FEM results. Why? Fig. 7b is the same as Fig. 6b, please replace it with the correct figure.
• Captions of Figs. 6 and 7 should be revised as these figures show the results for both the left and right sides of the wall (not only for the left panel). Also, the captions of both Figures should not read exactly the same.
• Figure 8: the curve corresponding to the measured results cannot be seen. Please be careful when choosing the symbols so that the measured and FEM results can be distinguished. This also applies to other Figures throughout the paper.
• Line 287: the word “require” does not make sense in this context. I suggest “result in” or “lead to”.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

All my comments have been taken into account.

Author Response

Thanks for all the comments!

Reviewer 2 Report

Title: Analysis of Working Performance of a Back-to-back Geosynthetics Reinforced Soil Wall

by Guangqing Yang, Yunfei Zhao, He Wang and Zhijie Wang

Applied Sciences, Manuscript ID: applsci-1442252 (re-review)

Although the authors replied to most comments, some important issues raised in the first round of the revision were not precisely addressed. The following few comments and corrections should be considered to clarify those issues as a condition to reach the study a further step and the option of an acceptable status for publication. This reviewer believes this will help the authors to improve the document enough for later publication.

• The uniaxial geogrid was simulated as a linear elastic material and the rheological behaviour was not taken into consideration in the analyses.
• The constitutive model parameters have not been entirely provided in Table 4. Additionally, used to simulate backfill behaviour.
• Some of the conclusions present in the paper depend on several other non-evaluated factors (eg.: external loading; soil compaction; type and stiffness of soil, facing, and reinforcement) and cannot be generalized. This should be mentioned in the paper.
• The English is poor and should be revised by a native speaker.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

The authors have significantly improved the manuscript based on my previous review comments. In my opinion, the paper can be published after moderate English editing (particularly in the Abstract, as elaborated below):  

• Abstract: The sentence in lines 15-17 is incomplete. Also, the sentence in lines 25-26 needs to be revised. What do you mean by “In addition, even with longer reinforcements and perform the same,”?

Author Response

Please see the attachment. Thank you!

Author Response File: Author Response.docx