GRIDMAT—A Sustainable Material Combining Mat and Geogrid Concept for Ballasted Railways

Round 1

Reviewer 1 Report

In this manuscript, to develop a novel GridMat technology which combined standard under-ballast mats with geo-grid designs, a group of tests were performed, including five aperture sizes and three void areas. The topic is interesting and the research method is acceptable. Generally, this manuscript is organized well and the writing is basically clear to readers. However, the following comments and suggestions should be addressed.

(1) In the introduction part, the description of research motivation should be enhanced. Please add some comments on the disadvantages of existing researches.

(2) Table 1 is suggested to re-designed.

(3) In Figure 2, please check the marked "y" between "60" and "70".

(4) In all equations, please use multiple signs instead of asterisk signs (*). 

(5) In Table 2, please add the detail code number and references for EN 13848.

(6) In Figures 4, 5, 6, and 9, please add the sub-figure number “(a)” and “(b)”.

(7) In Figures 7 and 8, the maximum train speed is up to 300 km/h, however, in this test the rail type is UIC-54 (line 116), which is usually not used for high speed railways.

 

Author Response

In this manuscript, to develop a novel GridMat technology which combined standard under-ballast mats with geo-grid designs, a group of tests were performed, including five aperture sizes and three void areas. The topic is interesting and the research method is acceptable. Generally, this manuscript is organized well and the writing is basically clear to readers. However, the following comments and suggestions should be addressed.

• In the introduction part, the description of research motivation should be enhanced. Please add some comments on the disadvantages of existing researches.

Following the suggestion of the reviewer, the introduction has been revised highlighting the disadvantages of existing solutions while clarifying the justification of the presented research. All changes can be see in red colour along the introduction, mainly in lines 52-57; 58-62; 75-91.

• Table 1 is suggested to re-designed.

Table 1 has been re-designed. In fact, it has been adapted to a “new” structure of the research showing two main steps: material design by assessing some key factors through laboratory tests; and the assessment of viability through simulations and LCA/LCCA analysis. Changes marked in red colour.

• In Figure 2, please check the marked "y" between "60" and "70".

It has been corrected. Thank you for checking.

• In all equations, please use multiple signs instead of asterisk signs (*). 

All equations have been corrected.

• In Table 2, please add the detail code number and references for EN 13848.

It has been added (changes in red colour).

• In Figures 4, 5, 6, and 9, please add the sub-figure number “(a)” and “(b)”.

It has been added.

• In Figures 7 and 8, the maximum train speed is up to 300 km/h, however, in this test the rail type is UIC-54 (line 116), which is usually not used for high speed railways.

Results of Figures 7 and 8 are calculated from theoretical estimations from results of the laboratory tests carried out in a box where the track is reproduced with a single piece of sleeper. In this test, the rail is only used to transmit the load from the machine actuator to the rest of components of the track section through the sleeper piece. Therefore, authors consider that the type of rail has little influence in this test. Only the foot dimensions could affect, but little differences can be seen between UIC54 and UIC60, while other factors like the moment of inertia (there is not load distribution between various sleepers) or the resistance to wear have not influence.

Thus, based on this, authors consider that the estimations in Figure 7 and 8 can stay up to 300 km/h. Also, it must be taken into account that the use of train speed up to 300 km/h has little influence on the trend for the impact of GridMat in comparison with standard mats or conventional tracks with no mats (main objective of these figures).

Reviewer 2 Report

In this paper, the design of Grid Mat: a sustainable technology for ballasted railways was investigated and compared to conditions of using Under ballast mats (UBM) and tracks without elastic solution under ballast. The purpose of this paper is to provide an effective and optimal solution to damping capacity while limiting the oscillations and settlement of the ballast layer. This research falls within the scope of the Journal. Despite considerable work made in this study, I believe this paper lacks sufficient explanations of (1) review of the literature (2) necessity of the paper (3) methodology (4) results and discussions. Specific reasons are stated in the following:

1   1-The novelty and necessity of the current study are questionable. Also, the literature review needs to be enhanced to show the limitations of previous studies.

2   2-Based on the contents stated in this study, it is strongly suggested that the title of the paper be changed based on the necessity and innovation of the paper.

3.  3- More views and figures of the test sample should be provided in the revised paper. A real view of the placement of Grid Mat on the test specimen and ballast box tests should be shown in the revised paper.

4   4-Position information of Grid Mat in ballast box tests should be clearly stated in the revised paper:

 4.1) Grid Mat placement status (depth) from the bottom of the sleepers

 4.2) the effect of moving the Grid Mat position (Placement depth changes) from the bottom of the sleepers on the results.

   4.3) optimal depth

   4.4) If the Grid Mats are used in several layers (for example, 2 layers), is it not more effective?

5  5-Based on the fourth comment, depending on the position of the grid mat, this material may be damaged during track maintenance (tamping). Please provide clear explanations in the revised paper.

6   6-The caption of Figure 6 is inconsistent with the Description of this figure. The details of the caption should be provided in the revised paper. The caption of the picture is explained the Settlement results for hard and medium Grid Mats according to the void area, while the hard mat was selected to study the influence of the void area.

7  7-The details of the calculation of LCA and LCCA for mat case studies should be presented in section 3.4. (Environmental and economic impacts).

8. 8-In the Analysis of results and discussion section, the graphs should be fully interpreted and the reason for the changes and differences in the values of Stiffness and relative settlement in different states (without a mat, for both types of Grid Mat) should be fully and clearly stated. It is not enough to state the generalities of the graphs.

9    9- Please explain the reason for using the standard deviation index (SD) in obtaining Maintenance frequency.

 

1    10- In an academic text, some explanations should be provided below each title and sub-title to describe what is presented in that section or sub-section. For instance, please provide some explanations below “2. Methodology”. Please check the whole manuscript to resolve this problem.

1    11- The introduction needs to strengthen by adding more papers including the following: 

       - Evaluation of airfield concrete block pavements based on 3-D modeling and plate loading test, Construction and Building Materials, 2021.

 

 

 

 

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Author Response

In this paper, the design of Grid Mat: a sustainable technology for ballasted railways was investigated and compared to conditions of using Under ballast mats (UBM) and tracks without elastic solution under ballast. The purpose of this paper is to provide an effective and optimal solution to damping capacity while limiting the oscillations and settlement of the ballast layer. This research falls within the scope of the Journal. Despite considerable work made in this study, I believe this paper lacks sufficient explanations of (1) review of the literature (2) necessity of the paper (3) methodology (4) results and discussions. Specific reasons are stated in the following:

1-The novelty and necessity of the current study are questionable. Also, the literature review needs to be enhanced to show the limitations of previous studies.

From reviewer comment, authors have revised the abstract and introduction of the paper to clearly show the justification of the research while presenting deeper literature review (some new references have been added) to state the advantages and disadvantages found in previous studies, which contextualizes the current research. All changes are marked in red colour along the abstract and introduction.

2-Based on the contents stated in this study, it is strongly suggested that the title of the paper be changed based on the necessity and innovation of the paper.

According to the suggestion of the reviewer, the title have been modified and adapted to the necessity of the paper.

3- More views and figures of the test sample should be provided in the revised paper. A real view of the placement of Grid Mat on the test specimen and ballast box tests should be shown in the revised paper.

As indicated by the reviewer, extra figures have been included for clearer illustration of laboratory test and position of mats into the box. Particularly, Figure 2 have been modified including a scheme of test configuration in section (b), while showing the configuration of the real laboratory test (in c) marking the position of the mats or GridMat tested in this study.

4-Position information of Grid Mat in ballast box tests should be clearly stated in the revised paper:

 4.1) Grid Mat placement status (depth) from the bottom of the sleepers

This has been specified in lines 175-182 (changes in red colour) where the thickness of the ballast layer have been indicated while describing that the GridMat were placed under the ballast, as done with the standard mats.

 4.2) the effect of moving the Grid Mat position (Placement depth changes) from the bottom of the sleepers on the results.

4.3) optimal depth

This parameter (GridMat depth under the ballast) was not considered in this study since the aim is to provide a solution to replace standard mats by using similar process of installation in railway tracks. Therefore, it was analysed the effect on including the GridMat directly over the platform and under the whole ballast layer.

This has been specified along the test while Table 1 has been improved to clearly show that the variable considered in this paper are (1) aperture size of the orifices in GridMat; and (2) number of orifices per m² of mat. 

   4.4) If the Grid Mats are used in several layers (for example, 2 layers), is it not more effective?

The reviewer presents an interesting point that will be considered in further studies focused on optimizing the installation and placement of the GridMat. This has been indicated at the end of the conclusions as further research since the present paper focuses on showing the ability and viability of GridMat as replacement of standard mats, and therefore, this paper comparing directly the GridMats with track sections with and without mats under the ballast layer.

5-Based on the fourth comment, depending on the position of the grid mat, this material may be damaged during track maintenance (tamping). Please provide clear explanations in the revised paper.

It has been specified in the methodology that the GridMats were placed under the ballast layer as done with the standard mats in order to compare both materials while avoiding possible modifications in construction process that could take place during installation of GridMat into the ballast layer, and the possible further incidences during maintenance operations (like tamping) during the service life. This has been specified in lines 175-182 (changes in red colour).

Also, as indicated previously, at the end of the conclusions it has been stated as further research line the study of the influence of GridMat at different depths, assessing the impact on performance and possible incidences during maintenance operations.

6-The caption of Figure 6 is inconsistent with the Description of this figure. The details of the caption should be provided in the revised paper. The caption of the picture is explained the Settlement results for hard and medium Grid Mats according to the void area, while the hard mat was selected to study the influence of the void area.

The caption of Figure 6 has been corrected to describe the illustration of part (a) and (b) showing the results of box test for a hard GridMat with different density of orifices.

7-The details of the calculation of LCA and LCCA for mat case studies should be presented in section 3.4. (Environmental and economic impacts).

As this is a comparative study what is shown in Figure 9, authors consider that the representation of results through percentages of change for each solution in reference to the conventional track (with no mat) is more representative and easier to interpret. This has been decided after studying the results and create different types of graphs, determining that the current graph is the most representative.

8-In the Analysis of results and discussion section, the graphs should be fully interpreted and the reason for the changes and differences in the values of Stiffness and relative settlement in different states (without a mat, for both types of Grid Mat) should be fully and clearly stated. It is not enough to state the generalities of the graphs.

Following the advice of the reviewer, authors have revised the whole analysis of results, improving the description of the graphs while avoiding generalities. Main changes are marked in red colour along the analysis of results. Details in lines 338-347, 353-356, 367-373, 394-396, 422-431.

9- Please explain the reason for using the standard deviation index (SD) in obtaining Maintenance frequency.

As suggested by the reviewer, explanation of the reason for using SD have been added in lines 216-223, indicating literature review using it, application by rail authorities and statement by European standards.

10- In an academic text, some explanations should be provided below each title and sub-title to describe what is presented in that section or sub-section. For instance, please provide some explanations below “2. Methodology”. Please check the whole manuscript to resolve this problem.

Following the recommendation of the reviewer, the whole manuscript have been reviewed to include explanation below each title and sub-title. Changes are marked in red colour along the manuscript.

11- The introduction needs to strengthen by adding more papers including the following: 

       - Evaluation of airfield concrete block pavements based on 3-D modeling and plate loading test, Construction and Building Materials, 2021.

This has been added in line 125, reference number 19.

Reviewer 3 Report

The manuscript deals with (GRIDMAT), sustainable material for ballasted railways. The authors have chosen an interesting topic. The manuscript language is acceptable. The structure of the manuscript is clear. The results are well explained and discussed.

Some of the important points are highlighted below:

1. An abstract is often presented separately from the article, so it must be able to stand alone. The abstract structure should be as follows: (introduction, problem of statement, materials, methods, results, and recommendations). I suggest revising the abstract.

2. There are some minor grammar mistakes such as line 44, I suggest checking the language of the manuscript.

3. Most of the figures' captions need to modify. For example, figure 1 needs to classify the captions to (a) and (b) and mention that in the figure. Same with figure 2, contains two different figures with only one caption.

4. The points presented in the conclusion section are not up to the mark. The authors are advised to revise it completely and try to present information, which is a summary of the important aspects discussed in the preceding sections. It certainly lacks in its current form. Also, I suggest the authors to delete the lines from 408 – 413 because it's repeated.

Author Response

The manuscript deals with (GRIDMAT), sustainable material for ballasted railways. The authors have chosen an interesting topic. The manuscript language is acceptable. The structure of the manuscript is clear. The results are well explained and discussed.

Some of the important points are highlighted below:

1. An abstract is often presented separately from the article, so it must be able to stand alone. The abstract structure should be as follows: (introduction, problem of statement, materials, methods, results, and recommendations). I suggest revising the abstract.

Following the suggestion of the reviewer, authors have revised the abstract. Main changes can be seen in red colour.

2. There are some minor grammar mistakes such as line 44, I suggest checking the language of the manuscript.

A native English speaking has revised the whole document.

3. Most of the figures' captions need to modify. For example, figure 1 needs to classify the captions to (a) and (b) and mention that in the figure. Same with figure 2, contains two different figures with only one caption.

Figures 1 and 2 have been modified as indicated by the reviewer while the captions have also been adapted. Also, authors have improved figures 4, 5 and 6 indicating part (a) and (b) of each figure, as indicated in the captions.

4. The points presented in the conclusion section are not up to the mark. The authors are advised to revise it completely and try to present information, which is a summary of the important aspects discussed in the preceding sections. It certainly lacks in its current form. Also, I suggest the authors to delete the lines from 408 – 413 because it's repeated.

Following the suggestion of the reviewer, the first paragraph of conclusion section (that was in lines 408-413 in original version) was deleted to avoid repeated parts. Also, all conclusion points have been revised and rewritten to provide the main findings and summary of the important aspects of preceding results. Voids are marked in red colour in conclusions section.

 

Round 2

Reviewer 2 Report

Most of the comments have been addressed.