Physical and Mechanical Behaviors of Compacted Soils under Hydraulic Loading of Wetting–Drying Cycles
Round 1
Reviewer 1 Report
This paper presents the results of a series of wetting-drying tests performed on a silty sand. The variation of suction, water content, void ration, and small strain shear modules of the soil samples during the tests have been monitored, and then thoroughly discussed in the paper.
The paper is generally good, and contains valuable test data that can be used for model development and verification. However, the quality of the work can be improved by addressing a few important issues listed below.
The literature review of the paper is incomplete. A more complete review of the literature is required to cover the main contributions, and clearly highlight the gap in the literature that this work is aimed to address. For example, volume change dependency of soil water retention curve is one of the main themes of this work, but several main references in this regard have not been mentioned/cited in the paper. For minimum, the following main references need to be included:
Pasha A. Y., A. Khoshghalb, and N. Khalili, (2017). "Hysteretic model for the evolution of water retention curve with void ratio.”, ASCE's Journal of Engineering Mechanics, 143(7).
Gallipoli, D., Wheeler, S. J., and Karstunen, M. (2003b). “Modelling the variation of degree of saturation in a deformable unsaturated soil.” Geotechnique, 53(1), 105–112.
Pasha, A., A. Khoshghalb and N. Khalili (2020). "Evolution of isochoric water retention curve with void ratio." Computers and Geotechnics 122: 103536.
Nuth, M., and Laloui, L. (2008). “Advances in modelling hysteretic water retention curve in deformable soils.” Comput. Geotech., 35(6), 835–844.
Khoshghalb, A., A. Y. Pasha and N. Khalili, (2015), “A Fractal Model for Volume Change Dependency of the Water Retention Curve.” Géotechnique, 62(2): 141-146
Pasha A. Y., A. Khoshghalb, and N. Khalili, (2019) “Can degree of saturation decrease during constant suction compression of an unsaturated soil?” Computers and Geotechnics, Volume 106.
Due to the volume change dependency of the retention behaviour of soils, the literature has moved away from using the term soil water “characteristic” curve (SWCC), since the curve is indeed not characteristic of a soil and depends on the state of the soil. The authors need to replace SWCC with SWRC throughout the manuscript.
Line 91-92: reporting the percentage of the silt and clay, and also the liquid and plastic limits of the soil with two decimal digits accuracy is basically meaningless. Those parameters are obtained in the lab using rough techniques and should not be reported with several decimal digits. Also, percentage sign is missing after the plasticity index figure. Similar “too accurate” figures have been also in several other parts of the paper, for example lines 115 to 125, 144 to 175, 290 to 310, and 315 to 328. These all need to revised.
In Figure 1, change the scale of the horizontal axis so that it only goes from 10-3 to 10-1 or 1mm, there is no need to include larger sizes as the soil does not contain large particles.
In the test set-up explained on page 3, the authors have mentioned that they have recorded vertical movements of the sample with a displacement sensor, but it is not clear how the lateral movement of the sample (i.e., change in the dimeter of the sample) has been measured in the tests. This is crucial for a correct estimation of void ratio of the sample during the test.
With reference to the small strain shear modulus of the soil, a few previous studies have shown that particle shape, the amount of silt particles, and also stress anisotropy also influence the shear modulus of the soils. It is useful to include a few references on this, and also a discussion on how (or if) these are incorporated in the relationships presented in page 13. A few main refences are below:
Payan, M, K. Senetakis, A. Khoshghalb, and N. Khalili (2017) "Effect of Gradation and Particle Shape on Small-Strain Young’s Modulus and Poisson’s Ratio of Sands." International Journal of Geomechanics, 17(5).
Payan, M, K. Senetakis, A. Khoshghalb, and N. Khalili (2017) " Characterization of the small-strain dynamic behaviour of silty sands; contribution of silica non-plastic fines content." Soil Dynamics and Earthquake Engineering, 102: 232-240
Payan M., A. Khoshghalb, K. Senetakis, and N. Khalili, (2016) “Small-Strain Stiffness of Sand Subjected to Stress Anisotropy”, Soil Dynamics and Earthquake Engineering; 88: 143-151.
Payan, M., K. Senetakis, A. Khoshghalb, and N. Khalili. (2016), "Influence of Particle Shape on Small-Strain Damping Ratio of Dry Sands"; Géotechnique 66(7): 610-616.
Payan, M., A. Khoshghalb, K. Senetakis, and N. Khalili (2016). "Effect of particle shape and validity of Gmax models for sand: A critical review and a new expression." Computers and Geotechnics 72: 28-41.
Interpretation of the SWRC when presented in term of gravimetric water content is tricky and error-prone, particularly when curves like those presented in Equations (2) and (3) are fitted to the data. This has been discussed in length in the reference below. The authors need to cite this article, and consider its recommendations when interpreting their data:
Pasha A. Y., A. Khoshghalb, and N. Khalili, (2016) Pitfalls in Interpretation of Gravimetric Water Content–Based Soil-Water Characteristic Curve for Deformable Porous Media. International Journal of Geomechanics: 16(6) D4015004.
A few minor comments:
Instead of “high intake ceramic disk”, use “high air entry value ceramic disk” which is more common in the unsaturated soil mechanics community.
Line 68-68: differences in water contents are given in cc, which is not correct. Also, lowercase c should be used in cc.
Finally, there are several pore sentences in the text, e.g. lines 47, 121, 134, 155, etc. The text will benefit from a careful proofreading.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript presents a study on the wetting-drying behaviour of a highly compacted soil specimen. Authors have used the pressure plate apparatus to conduct the study and performed several wetting-drying cycles to measure the changes in void ratio, moisture content and degree of saturation. The experimental results reported are interesting and are useful to geotechnical engineers and researchers. However, there few amendments authors need to undertake before the manuscript can be published.
1. L89: Mention the location of the Yellow River. City, country etc.
2. Use the more common term ‘degree of saturation’ rather than ‘saturation degree.’
3. L182 – 184: Check the symbols. Same symbol is used for matric suction and also as a model parameter.
4. Figure 6: Correct the legend. Colours in the legend do not match with the graph.
5. Figure 6: Why is the initial wetting phase not included?
6. L232-237: Is this true for the complete suction range between 0 – 1000 kPa, especially in the first wetting cycle when soil was initially saturated? Can you identify the air entry value by comparing the decrement in void ratio and drained water volume?
7. Figure 10: Improve the quality of the figure. Axes labels are illegible.
8. Proofread the paper thoroughly for grammar and spelling mistakes. Some are listed below.
a. L101: intake valve was equipped…
b. L136: .. void ratio..
c. L186: ‘… are presented…’
d. L337: ‘…are listed…’
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors have addressed my comments satisfactorily. I now recommend the manuscript for publication.
