Shear Strength and Seepage Control of Soil Samples Used for Vertical Barrier Construction—A Comparative Study
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe current study considers three barrier technologies through a series of consolidated drained triaxial tests and permeability coefficient tests on soil samples collected. The study is interesting and highlights a critical issue. However, some problems that need to be addressed have been identified. In this context, it would be appropriate to make revisions considering all of the following recommendations.
-The parameters used in the three-axial test described in Section 2.2 section should be detailed, and the technological characteristics of the device (fully automatic, etc.) should be presented.
-Providing additional explanations for the abbreviations used in Table 1 in the form of footnotes immediately below the table will make it easier for readers to understand. It is recommended that this be done.
-The reasons for selecting the chosen methods (DSM, LPG and VBSW) should be explained more clearly and in greater detail.
-More detailed information should be provided on load and parameter selection in consolidation, permeability, and shear tests.
-While the triaxial test provides faster results and pore pressure calculations can also be performed, it would be useful to provide information about the reasons for choosing the CD test and its advantages over the CU test.
-In the Results section, a comparative explanation of the effects of using barriers after Figure 5 would increase the communicative power of the study. It is recommended that this section be added.
-Presenting a secondary value such as RMSE along with R2 in the graphs would make the statistical evaluation more robust. I recommend that the authors consider adding this.
-The originality and novel aspects of the study should be presented more clearly.
-It is recommended that the Conclusion section be presented in bullet points showing clear results rather than in a single paragraph. Also, this section should be improved, and the impact of the findings on the final results should be clearly highlighted.
-There are some errors in expression and spelling throughout the study. It is recommended that the article be reviewed in accordance with grammar rules in order to correct such errors.
Comments on the Quality of English LanguageThe English could be improved to more clearly express the research.
Author Response
The authors would like to express their appreciation for the valuable suggestions and comments that improved the scientific soundness and quality of the manuscript. The authors would like to assure all the Reviewers that the paper was proofread, carefully reviewed, double-checked and corrected, addressing all the Reviewers’ general and specific comments. Below you will find detailed answers to suggested revisions.
Reviewer 1
Specific comment:
The parameters used in the three-axial test described in Section 2.2 section should be detailed, and the technological characteristics of the device (fully automatic, etc.) should be presented.
Answer:
The tests were conducted in a standard triaxial apparatus equipped with an additional module – a flow pump, equipped with rods and a rigid connection between the cell and the piston rod. Saturation was performed using the equalization pressure > 250 kPa, followed by consolidation and then shearing in CD conditions at a rate determined according PN-EN ISO 17892-9:2018-05, with a shear rate lower than 0.001 mm/min. Section 2.2 no includes a more specific explanation of the triaxial testing procedure and additional reference is added where the authors presented the set up in full scale. The triaxial test rig is presented on Figure 1, with all components described in the figure. (Lipiński, M.J.; Wdowska, M.K.; Wudzka, A. Capability of Triaxial Apparatus with Respect to Evaluation of Nonlinearity of Soil Stiffness. Archives of Civil Engineering; 2020, 66, 69–80, doi:10.24425/ACE.2020.131775). For changes please see revised copy of the manuscript l. 201-214.
Specific comment:
Providing additional explanations for the abbreviations used in Table 1 in the form of footnotes immediately below the table will make it easier for readers to understand. It is recommended that this be done.
Answer:
The authors agree that the abbreviations should not only be explained in the main text but also in the table. The footnote is added: *VBSW- vibrated beam slurry walls, DSM- deep soil mixing, LPG low- pressure grout injection.
Specific comment:
The reasons for selecting the chosen methods (DSM, LPG and VBSW) should be explained more clearly and in greater detail.
Answer:
The main reason for analyzing these three specific methods is that according to literature review and to the best of authors theoretical and practical knowledge these are the methods most commonly used in engineering practice. These has supported by additional publications referred in the text [3, 10]. Important for the research was also the fact the investigated methodologies were those which a commercial partner collaboration with the Institute that the authors are representing was capable of performing on the site. These three methods were used to compare the efficiency between them. A brief explanation is now added in the main text. For details please refer to the revised copy of the manuscript. (l.176-178).
Specific comment:
More detailed information should be provided on load and parameter selection in consolidation, permeability, and shear tests.
Answer:
Saturation was performed using the equalization pressure > 250 kPa, followed by consolidation at effective stress 100, 200 and 400 kPa and then shearing in CD conditions for same confining pressure at a rate determined according PN-EN ISO 17892-9:2018-05, with a shear rate lower than 0.001 mm/min. Such conditions would represent the in situ conditions expected in case of the critical scenario expected at the site during extreme events. Such information in no provided in in section 2.2 and the effective stresses are included in Figure 2. Please see revised copy of the manuscript.
Specific comment:
While the triaxial test provides faster results and pore pressure calculations can also be performed, it would be useful to provide information about the reasons for choosing the CD test and its advantages over the CU test.
Answer:
The reason for choosing triaxial CD tests is that provide a wider understanding of shear strength and volume change behavior than consolidated drained tests. The CD test allows controlled stress conditions that reflect in situ scenarios experienced in flood prevention systems like in this study. During the triaxial tests, effective stress levels can be modified to simulate the stresses observed in field conditions. The ability to replicate field conditions increases the predictive reliability of the strength parameters critical for dam design.
Furthermore, the consolidated drained triaxial tests are performed for both consolidation and drainage phases, reflecting the time-dependent behavior of soils. The changes in volume can significantly influence the interpretation of soil response and strength. Such accuracy is crucial especially for impermeable soils that are subjected to hydraulic pressures, like in the case present stud. Since these soils are not only stressed under conventional conditions but also undergo volumetric changes that could affect seepage characteristics within the dam or dyke structure. Brief explanation is now added in the main text, please see l. 208-214.
Specific comment :
In the Results section, a comparative explanation of the effects of using barriers after Figure 5 would increase the communicative power of the study. It is recommended that this section be added.
Answer:
Additional paragraph in Results section 3.1 is added, all parameters comparing the performance of each barrier type is now presented in more details in Table 2.
“Shear strength tests confirm that vertical barrier systems—whether constructed using vibrating beam slurry walls (VBSW), deep soil mixing (DSM), or low-pressure grout injection (LPG)—lead to improvements in the mechanical performance of soils. Triaxial testing consistently recorded increases in the angle of internal friction (φ′) by approximately 3–6° in treated samples compared to untreated ones, with values rising from 30°–32° to 35°–38° for soils with a plasticity index (PI) of about 3.5%. The highest values of angle of internal friction though was measured for VBSW technology. When it comes to soil type however, the improvement is most evident in those of lower plasticity, suggesting that barrier technologies provide stronger reinforcement under such conditions giving the lowest values for LPG for same soil type used for construction of the barrier. In contrast, soils with higher plasticity shows a smaller relative increase in φ’.”. Please see l. 313-322.
Specific comment:
Presenting a secondary value such as RMSE along with R2 in the graphs would make the statistical evaluation more robust. I recommend that the authors consider adding this.
Answer:
At the initial stage of the research the authors considered statistical analyses to be included in the study however, due to a small number of samples that were eventually used for final evaluation (11 treated soil samples and 11 untreated soil samples) this idea was abounded. Such small group would not be statistically representative and drawing the conclusion from it would not be scientifically justified. The small number of samples at the stage of laboratory testing was reduced due to the quality of some of them (damage during transport and storage).
Specific comment:
The originality and novel aspects of the study should be presented more clearly.
Answer:
To enhance the sound of novelty of the study the introduction and conclusion section was improved by adding new text in l. 167-171 and l. 423-426 in the new copy of the manuscript.
Specific comment:
It is recommended that the Conclusion section be presented in bullet points showing clear results rather than in a single paragraph. Also, this section should be improved, and the impact of the findings on the final results should be clearly highlighted.
Answer:
The conclusion section was rewritten and key findings were presented as a bullet points
Specific comment :
There are some errors in expression and spelling throughout the study. It is recommended that the article be reviewed in accordance with grammar rules in order to correct such errors.
Answer:
The authors would like to assure that the entire text was carefully revised and all the grammar and style errors were corrected.
The authors would like to take this opportunity and express their great appreciation for providing such detailed reviews and for all the Reviewers’ and the Editor's efforts put in improving the manuscript for better scientific sound and presentation. The authors would like to ensure that all the corrections were implemented and all general and specific comments were addressed in the revised copy of the manuscript.
With best regards,
Authors of the manuscript
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe study presents a comparative evaluation of three barrier technologies; however, the research objectives could be more clearly defined in the introduction. Consider explicitly stating the hypotheses or research questions guiding the comparative analysis. Further following major comments should be addressed before the next round of review.
The abstract is dense but does not provide key quantitative results. It should discuss some key results.
The novelty of the research is not sufficiently highlighted. It would strengthen the manuscript to explain how this study advances beyond existing literature or presents new insights into barrier performance in specific soil types.
Figures 3 to 9 illustrate the experimental findings, but several figures lack detailed captions and units on axes, which may confuse readers. Enhancing figure clarity and adding legends or annotations would improve comprehension.
The discussion briefly touches on key findings, but it lacks critical comparison with existing studies. Expanding this section by incorporating more literature and discussing potential limitations or variability in field applications would strengthen the scientific value. Also some lines needs to supported by relevant studies e.g., lines: 44-47: https://doi.org/10.1007/s13369-018-03693-7; Lines 81-83: https://doi.org/10.1007/s12205-022-2088-8
Terms such as pure soil, untreated samples, and natural soil are used interchangeably. Standardizing this terminology throughout the manuscript would enhance clarity.
The flow-pump test setup and back-pressure saturation methodology are well described, but the statistical reliability of results (e.g., standard deviations or confidence intervals) is not addressed. Including this would help assess reproducibility and significance.
The paper suggests that barriers are more effective in granular soils. However, the mechanistic explanation for this observation is not thoroughly discussed. Adding a brief interpretation based on soil structure or barrier-soil interaction would be valuable.
The manuscript is generally well-written, but minor grammatical issues and overly long sentences occur throughout. A language edit for sentence structure, punctuation, and flow would enhance readability.
Author Response
ANSWERS TO COMMENTS
The authors would like to express their appreciation for the valuable suggestions and comments that improved the scientific soundness and quality of the manuscript. The authors would like to assure all the Reviewers that the paper was proofread, carefully reviewed, double-checked and corrected, addressing all the Reviewers’ general and specific comments. Below you will find detailed answers to suggested revisions.
Reviewer 2
Specific comment:
The abstract is dense but does not provide key quantitative results. It should discuss some key results.
Answer:
The abstract was improved by providing more specific outcome of the study. Please see revised copy of the manuscript (l. 22-26)
Specific comment:
The novelty of the research is not sufficiently highlighted. It would strengthen the manuscript to explain how this study advances beyond existing literature or presents new insights into barrier performance in specific soil types.
Answer:
The novelty of the study lays in employing combined geotechnical and hydraulic tests to assess impermeable barrier technologies. Comparison of three methods highlights their respective application limits across different soil types and consistency. Important to notice is the fact the the samples were collected in situ conditions and are not reconstituted as it happens in most cases presented in laboratory. The novelty was highlighted in Introduction and Conclusion sections. For details please see l. 167-171 and l. 423-426 in the revised copy of the manuscript.
Specific comment:
Figures 3 to 9 illustrate the experimental findings, but several figures lack detailed captions and units on axes, which may confuse readers. Enhancing figure clarity and adding legends or annotations would improve comprehension.
Answer:
The authors would like to appreciate such careful revision. In did some of the figures (i.e Fig. 5 and 6) missed the units and they are now replaced with corrected copies. In Fig. 9 the authors present the change of coefficient of permeability that is represented without units due to calculation procedure where in the division the units were reduced. The revise copy now includes figures with corrected and consistent presentation of units.
Specific comment:
The discussion briefly touches on key findings, but it lacks critical comparison with existing studies. Expanding this section by incorporating more literature and discussing potential limitations or variability in field applications would strengthen the scientific value. Also some lines needs to supported by relevant studies e.g., lines: 44-47: https://doi.org/10.1007/s13369-018-03693-7; Lines 81-83: https://doi.org/10.1007/s12205-022-2088-8
Answer:
As suggested the missing citations were added. The key findings are now exposed more in introduction and conclusion section. More literature is added what improved the discussion [1, 2, 4, 8, 31]. For details please see the revised cop.
Specific comment:
Terms such as pure soil, untreated samples, and natural soil are used interchangeably. Standardizing this terminology throughout the manuscript would enhance clarity.
Answer:
The authors fully agree that the terminology should be consistent so the research approach is easy to follow. The term “untreated samples” is now used along the entire text.
Specific comment:
The flow-pump test setup and back-pressure saturation methodology are well described, but the statistical reliability of results (e.g., standard deviations or confidence intervals) is not addressed. Including this would help assess reproducibility and significance.
Answer:
As a matter of fact, the authors initially planned to incorporate statistical analyses into the study however, this approach was abandoned because the final dataset—11 treated and 11 untreated soil samples—was too limited to provide statistically representative results or scientifically valid conclusions. The small sample size was further constrained during laboratory testing, as several specimens were damaged during transport and storage and could not be used. The authors plan to extend the research in the near future and employ statistical analyses to make the research finding more reliable in terms of significance and reproducibility.
Specific comment:
The paper suggests that barriers are more effective in granular soils. However, the mechanistic explanation for this observation is not thoroughly discussed. Adding a brief interpretation based on soil structure or barrier-soil interaction would be valuable.
Answer:
The vertical impermeable barriers are particularly suited for granular soils because of their hydrodynamic properties, which are influenced by the higher permeability of granular media, the barrier's structural impact on hydraulic gradients, and the retention abilities influenced by the properties of the interaction materials. These factors collectively ensure that the contaminants are better contained within granular settings than would be achieved in cohesive soils. When barriers are installed in granular soils, the less restrictive nature of porous deposits allows the barriers to control and redirect groundwater movement more effectively than in cohesive soil layers, where seepage can lead to pressure build-up and failures. The efficiency of vertical impermeable barriers in granular soils is further underscored by the hydrodynamics involved during pressure application and the resultant flow beneath and around barriers. Light non-aqueous phase liquids accumulate around barriers in descending groundwater flows, what affects structural integrity to prevent leakages and ensure stability over time. Brief explanation of such behavior was included in discussion section. Please see l. 397-401.
Specific comment:
The manuscript is generally well-written, but minor grammatical issues and overly long sentences occur throughout. A language edit for sentence structure, punctuation, and flow would enhance readability
Answer:
The authors would like to assure that the manuscript was carefully revised for inspection of any grammar and style errors. We strongly believe that now the manuscript meet mdpi publication standards.
The authors would like to take this opportunity and express their great appreciation for providing such detailed reviews and for all the Reviewers’ and the Editor's efforts put in improving the manuscript for better scientific sound and presentation. The authors would like to ensure that all the corrections were implemented and all general and specific comments were addressed in the revised copy of the manuscript.
With best regards,
Authors of the manuscript
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsDear Authors,
the topic and the experimental approach have been appreciated, and the novelty of investigation is present. There is a need to better focus the distinction between lab scale and real scale, and the possible practical problems that could be encountered during the use of the technolgy on different geological formations. The comparison of soil behaviour for the barrier should be also linked to the type of soil and groundwater flow regime. Environmental issues are welcome for SDG, such as reuse of aggregates or muck soils.
Some suggestions below.
Regards
1 - Keyword: geotechnical structure seems too much generic
2 - Comment on grain size distribution and selection of soil.
3 - Fig. 1 check spelling of components
4 - Fig. 5: why lines extend outside the left part of the stress chart?
5- barier in red should be barrier
6 - fig 7 it is flow and not folw
7 - table 1 and 2 : in caption recall the soil types
8 - Discussion and Conclusions: (a) is it possible to use also recycled aggregates in a circular economy approach instead of raw materials? (b) Should be more effective in terms of application / suggestions, not only recap, considering the passage from lab scale to real scale (c) suggestions on operative solutions and equipment to build barriers?.
9 - References: the list is very essential. Two suggestions to extend background and applications.
(a) D. Basu, et al. , Analytical solutions for consolidation aided by vertical drains, Geomechanics Geoengin., 1 (1) (2006), pp. 63-71.
Author Response
ANSWERS TO COMMENTS
The authors would like to express their appreciation for the valuable suggestions and comments that improved the scientific soundness and quality of the manuscript. The authors would like to assure all the Reviewers that the paper was proofread, carefully reviewed, double-checked and corrected, addressing all the Reviewers’ general and specific comments. Below you will find detailed answers to suggested revisions.
Reviewer 3
Specific comment 1:
Keyword: geotechnical structure seems too much generic
Answer:
The keyword “geotechnical structures” was replaced with more specific term “flood prevention structures”. For detailed revisions please see corrected copy of the manuscript.
Specific comment 2:
Comment on grain size distribution and selection of soil
Answer:
The grain distribution parameters and grain sizes are provided in Table 1. Brief comment of soil types and their classification is now provided in the main text in the section 2. For details please refer to the main text of new copy of the manuscript (l. 181-183).
Specific comment 3:
Fig. 1 check spelling of components
Answer:
The spelling of each component was revised and corrected and the figure was replaced with the revised copy. Thank you for such detailed revision.
Specific comment 4:
Fig. 5: why lines extend outside the left part of the stress chart?
Answer:
Fig. 5 was corrected and replaced. Please see the revised manuscript for changes.
Specific comment 5:
barier in red should be barrier
Answer:
Thank you for pointing the typo. The labels on all the figures were revised and corrected where necessary.
Specific comment 6:
fig 7 it is flow and not folw
Answer:
Specific comment 7:
table 1 and 2 : in caption recall the soil types
Answer:
The authors used the standardised soil symbols according to Eurocode 7. They are commonly used in geotechnical and geological engineering practice globally. To avoid the confusion the authors used the footnote referring to appropriate soil classification standards.
Specific comment 8:
Discussion and Conclusions: (a) is it possible to use also recycled aggregates in a circular economy approach instead of raw materials? (b) Should be more effective in terms of application / suggestions, not only recap, considering the passage from lab scale to real scale (c) suggestions on operative solutions and equipment to build barriers?.
Answer:
Although SDG was not a major goal to address in the present study, nor the efficiency of the technology used for certain barriers technology used in practice, the authors improved the discussion section by pointing out the importance of sustainable development if flood prevention. Authors highlighted the fact the use of alternative materials like debris from demolition or fly ash as a combustion by-product could be effectively used as an alternative material for improving the performance of vertical barriers used in hydraulic structures. For revised discussion please see l. 412-418 in corrected copy of the manuscript.
Specific comment 9:
References: the list is very essential. Two suggestions to extend background and applications.
(a) D. Basu, et al. , Analytical solutions for consolidation aided by vertical drains, Geomechanics Geoengin., 1 (1) (2006), pp. 63-71.
Answer:
Thank you for the suggestion, the revised copy include the proposed reference in the Introduction.
The authors would like to take this opportunity and express their great appreciation for providing such detailed reviews and for all the Reviewers’ and the Editor's efforts put in improving the manuscript for better scientific sound and presentation. The authors would like to ensure that all the corrections were implemented and all general and specific comments were addressed in the revised copy of the manuscript.
With best regards,
Authors of the manuscript
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsIt has been observed that the requested changes have been made after revision. The article is acceptable.
Reviewer 2 Report
Comments and Suggestions for AuthorsAccepted. Congratulations.
