Modified Equation of Shear Strength with Respect to Saturation
Round 1
Reviewer 1 Report
applsci-2288181 – Review
An Improved Equation of Shear Strength with Respect to Saturation
General comment:
The paper presents the laboratory test results and analysis of the influence of saturation on shear strength of cohesive soils. The modified equation of shear strength for unsaturated soils was elaborated and evaluated based on the test results from two testing systems: pressure plate apparatus for determination of soil-water characteristic curve and triaxial apparatus for shear strength determination for soils with different saturation. The modified equation was introduced using combined effect of the relationship between matric suction and the degree of saturation together with the relationship between effective stress parameter and the degree of saturation. The shear strength for unsaturated soils with different degree of saturation obtained from the triaxial tests was compared with the shear strength calculated from the modified equation.
Title of the paper should be changed:
Modified Equation of Shear Strength with Respect to Saturation
In my opinion, the paper text should be supplemented with additional information and short comments on:
· Table 1. Physical properties of silty sand presented in Table 1 are not consistent. Silty sand is not characterized by liquid limit LL=52.4% and plastic limit PL=30.7% as well as permeability coefficient k=1.74 ∙ 10-10 m/s. Are you sure that the particle composition of the tested soil shown in Table 1 is correct?
· The method of determining the degree of saturation in pressure plate tests and triaxial tests requires additional explanation.
· Results of triaxial tests shown in Figures 10-12, specially concerning cohesion and angle of internal friction are surprising. Additional Figures and comments should be added to show method of evaluation of shear strength from CU and CD triaxial tests, for example using total and effective stress pathes.
Detailed comments and suggestions:
Figures 1: the caption of the Figure should be corrected
Figures 3, 9, 16, 20: the caption of the Figures should be corrected: add ?
Figures 8, 9, 12, 13, 15, 16, 17, 18, 19, 20, 21: X-axis should be corrected: Saturation (%)
Figures 3, 9, 16, 20: Y-axis should be corrected: add ?
Pages 5, 8, 9: is: g/cm3; should be: t/m3
Page 5: is: K x 10-8 (cm s-1); should be: k x 10-10 (m s-1)
Page 6, 8, 9: is: cm; should be: mm
Comments are also marked in the reviewed manuscript.
The paper after correction should be re-reviewed.
Sincerely
Reviewer
Comments for author File: 
Comments.pdf
Author Response
The authors would like to appreciate your time and kind efforts to evaluate this research paper and acknowledge your valuable comments advising us of its shortcomings and inspiring us to enhance its quality. Detailed answers to your comments are provided below and the manuscript has been altered where necessary. The changes that have been made in the manuscript are colored in RED. We believe the following answers and the revised manuscript cover your points of concern appropriately.
Author Response File: 
Author Response.docx
Reviewer 2 Report
1. Your model (Eq. 5) is directly Bishop’s equation (1), where metric suction is given by Van Genuchten formula (Eq.2), and effective stress parameter c is given by Kim et al. [31]. This should be more clearly stated in the article. Is it a new model?
2. Axes description in Figures: 2, 3, and 8-22 should be corrected in the same way as the axis description in Figure 1.
3. In Fig.22, the ranges of parameter values x2, x3, x4 and m should be given and commented on in the text.
Author Response
The authors would like to appreciate your time and kind efforts to evaluate this research paper and acknowledge your valuable comments advising us of its shortcomings and inspiring us to enhance its quality. Detailed answers to your comments are provided below and the manuscript has been altered where necessary. The changes that have been made in the manuscript are colored in RED. We believe the following answers and the revised manuscript cover your points of concern appropriately.
Author Response File: Author Response.docx
Reviewer 3 Report
The purpose of this research is to propose a new shear strength model for unsaturated soil and predict shear strength by using the degree of saturation directly. And this study focused on Bishop’s shear strength theory and van Genuchten’s soil-water characteristic curve to describe the effect of saturation on shear strength. This manuscript is well written and innovative. However, there are some minor problems with this manuscript. This manuscript can be received after minor revision:
(1) In the introduction: What are the innovative of this research?
(2) Fig. 4 and Fig. 5 are the same device, and you only need to place one picture.
(3) In line 178: The effective confining pressure set by the author is very low. Why does the author not conduct the triaxial shear test under high pressure?
(4) In line 184: “the consolidated drained triaxial test (CU test)” Did the author carry out the draining test (CD test) or the undraining test(CU test)?
(5)In lines 203-204: That’s why matric suction increases with an increasing degree of saturation. This description does not match the results in the Fig. 8. In addition, the authors can refer to the following article on the effect of compactness on matric suction:
SWCC of calcareous silty sand under different fines contents and dry densities. Frontiers in Environmental Science. 2021, 9: 682907. DOI:10.3389/fenvs.2021.682907.
(6)In lines 219-221: ‘When the saturation degree increases, the absorption between the soil layer and particles increases then cohesion increases’. Why does this happen? Is it due to capillary suction?
(7)In lines 226-232: The intergranular occlusion effect also has an important influence on the internal friction angle of unsaturated soil. It is suggested that the author refer to the following documents to improve this analysis.
Interlocking mechanism of calcareous soil. Rock and Soil. 2018, 39(9): 3113–3120. (EI)
(8) In the conclusions: The conclusion is too long, just state the key results.
Author Response
The authors would like to appreciate your time and kind efforts to evaluate this research paper and acknowledge your valuable comments advising us of its shortcomings and inspiring us to enhance its quality. Detailed answers to your comments are provided below and the manuscript has been altered where necessary. The changes that have been made in the manuscript are colored in RED. We believe the following answers and the revised manuscript cover your points of concern appropriately.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
applsci-2288181 – Review_v2
Modified Equation of Shear Strength with Respect to Saturation
In my opinion physical properties presented in Table 1 are still incorrect. If the authors are sure that the grain size curve shows silty sand then the values of liquid limit LL=52.4% and plastic limit PL=30.7% are incorrect. See plasticity index PI = LL - PL = 21.7%. Is it OK for silty sand? In my opinion the values of liquid limit LL and plastic limit PL should be removed from the Table 1.
The authors provided a brief explanation of the method used to determine the strength parameters c and φ, however, without presenting the results of individual CU and CD triaxial tests using total and effective stress paths, it is difficult to assess results of triaxial tests shown in Figures 10-12.
Sincerely
Reviewer
Author Response
The authors would like to appreciate your time and kind efforts to evaluate this research paper and acknowledge your valuable comments advising us of its shortcomings and inspiring us to enhance its quality. Detailed answers to your comments are provided below and the manuscript has been altered where necessary. The changes that have been made in the manuscript are colored in RED. We believe the following answers and the revised manuscript cover your points of concern appropriately.
Author Response File: Author Response.docx
