Stability Analysis of Expansive Soil Slope Considering Seepage Softening and Moistening Expansion Deformation
Round 1
Reviewer 1 Report
please find the attached file
Comments for author File: 
Comments.pdf
Author Response
Dear Reviewer:
Thank you for the reviewers’ comments concerning our manuscript (ID: water-809314). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in gray in the paper.The response includes a chart, see the attachment for details.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The contribution deals with an interesting and current topic. I believe that the authors should better discuss the results achieved in the points listed in the conclusions and to expand the literature on the subject in the introductory part.
Author Response
Dear Reviewer:
Thank you for the reviewers’ comments concerning our manuscript (ID: water-809314). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in gray in the paper. The main corrections in the paper and the responds to the reviewer’s comments are as flowing.
Responds to the reviewer’s comments:
-The contribution deals with an interesting and current topic. I believe that the authors should better discuss the results achieved in the points listed in the conclusions and to expand the literature on the subject in the introductory part.
Answer: Thank you for your patience and valuable suggestions. All your suggestions are very important. They have important guiding significance for my paper writing.
In the original paper, the conclusion is not clear enough to summarize the research results. In new revision, the main conclusions of this paper can be summarized as follows:
1.In this paper, the properties of expansive soil after dry wet cycle are analyzed in detail. In the aspect of fracture development law, after the first to the second circulation, the surface fracture rate increases most obviously, and then tends to be stable gradually. In terms of strength and permeability, the dry wet cycle mainly reduces strength and increases permeability by destroying the structure of expansive soil. After three cycles, the cohesion is reduced by half, the internal friction angle changes little, and the soil property is basically stable. At the same time, the permeability coefficient is increased by an order of magnitude.
2.The expansion and softening of expansive soil have a great influence on the slope stability after rainfall. Considering the influence of these two factors, the displacement of slope increases by an order of magnitude. From the change rule of stability coefficient, it can be seen that the expansive soil slope with good stability may lose stability after one or two rainfall.
3.According to the calculation, the sliding surface of the expansive soil slope develops along the bottom of the weathering zone. With the increase of the number of dry and wet cycles, the strength of expansive soil in the weathering area decreases, and the sliding surface becomes shallow. The results of calculation can explain the shallow and tractive properties of expansive soil landslide.
4.During rainfall infiltration, the saturation of the lower part of the slope changes the most. The effect of moistening expansion leads to a rapid rise in horizontal stress, but little change in vertical stress. The large increase in horizontal stress is the main reason for slope failure.
5.In conclusion, in the construction of road slope in expansive soil area, construction in rainy season should be avoided as much as possible. Or take effective measures of slope water isolation, strictly control the amount of rainwater infiltration, and prevent the soil from further softening and expansion.
In the new revision, the conclusion has been modified and marked in gray.
In the introduction part of the paper, some representative papers are introduced and references are added. Eg, Alonso's research is indispensable for the study of expansive soil, and his main research results and BExM model have been added to the paper.
Some other problems have been corrected in the revised paper, Thank you again for your review.
Author Response File: Author Response.docx
Reviewer 3 Report
Dear authors, thank you for this interesting contribution. My comments mainly refer to the section 4 numerical modelling and some comments on the experiments.
Please make clear, when referring to calculation results and when to experimental results. This is sometimes not clear to the reader.
- I'm missing a clearer description of the model, e.g. which software was used, what were the calculation steps, what was the constitutive model (Table with all the parameters), how was to seepage considered, how were time effects considered, how was the change in material parameters considered, how did you apply dry and wet steps, a.s.o. Also a sketch of the model with the layers, the groundwater level and the boundary conditions would help the readers to understand.
- I do not understand what you mean with the term 'failure'. You calculate displacements related to your parameters and somehow related the to stability and failure. How has this been done? Did you get the factors of safety through a strength reduction technique?
- You mention several times 'in comparison to the slope without moistering expansion'. Where are those results?
- Section 2: How many samples were investigated? You have 6 different sample preparation methods due to the cycles. For preparation type you need 4 samples for the shear test and one sample for the determination of the permeability. I'm I right?
See here some more detailed comments:
Line 70-71: You describe 3 layers, the weathered layer, the unweathered layer and the unweathered layer. This is not clear to me.
Line 98: What does this small circle with the 3 inside mean? This should refer to a Figure.
Line 100: I don't think, you can measure the thickness of layer in average up to 2 digits.
Please rephrase th beginning of section 2.2.1. This sounds more like an working instruction, than like a scientific paper. There are also some grammar issues here. In total you need 4 days for are cycle?
Line 129: What do you mean with 'marked before the test'?
Line 157-164 is there twice.
Fig. 6 and Fig.9 Please add also the tau/sigma diagrams to show the correlation between the results of the single load steps of the shear tests.
Line 222: It is wrong to mention dilatancy in this context.
Line 229-232: Please rephrase.
Line 242-243: Please rephrase.
Equation 3: Please add citation and us the same letter for saturation as above (Sr).
Line 285-286: Those lines are there twice.
Line 195: Please rephrase.
Equation 9: What is Theta? It would be nice to have a graph or a table to show directly the correlation between humidity filed and temperature field.
Line 340-342 and Fig. 9: I don't think a linear fit is appropriated if you want to show and represent the sudden drop. You should make the fit without the drop.
Line 366-368: Please rephrase.
Line 369: You should refer to Tab. 4
Table 4 is not clear to me. What is the content of this table?
Line 464: Please show the coincidence with the failure surface.
Fig. 16: This Fig. would be easier to get if you flip the axes.
Line 441: You say, your modeled deformation is too small. Too small in comparison to what?
Author Response
Dear Reviewer:
Thank you for the reviewers’ comments concerning our manuscript (ID: water-809314). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in gray in the paper.
The response includes a chart, see the attachment for details.
Author Response File: Author Response.docx
Reviewer 4 Report
The authors adress an important issue in geotechnical engineering of slopes exposed to alternating rainfall and drying and successive loss of stability and possible landslides. A sound description of case studies or history however is missing.
In practice natural soil slopes will always be exposed to rainfall and drying. How to explain failures that occur already after 1 or 2 wet-dry cycles? Only after recent excavation? Please explain.
Lab tests and numerical simulations are presented. however it is not clearly applied or demonstrated with field observations or actual cases of landslides. Please add.
Figures and tables should be explained in more detail.
I am sure this can be improved.
See attached document.
Comments for author File: Comments.pdf
Author Response
Dear Reviewer:
Thank you for the reviewers’ comments concerning our manuscript (ID: water-809314). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in gray in the paper.
The response includes a chart, see the attachment for details.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Unfortunately the authors missed again any discussion about the effect of heterogeneity.
To my opinion, the submission could be accepted for publication only after this brief discussion
Author Response
Dear Reviewer:
Thank you for the reviewers’ comments concerning our manuscript (ID: water-809314). Your opinion is very front-edge and important. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in blue in the paper.
- discussion about the effect of heterogeneity.
This article adds two introductions to Hicks M A's paper. Hicks, M. A[14]-[15] studied the influence of heterogeneity on the reliability and failure of two-dimensional and three-dimensional long slopes by finite element method. He found that the change of parameters has an important influence on the stability and failure mode of the slope. In the following stability analysis section, the influence of heterogeneity on the slope is briefly discussed.
Thank you again for your patience and valuable comments.
Author Response File: Author Response.docx
Reviewer 3 Report
Thank you for this improved version.
Author Response
Thank you again for your patience and valuable comments.
Reviewer 4 Report
Please make clear in introduction that application of this study is in the stability assessment of excavations in so called expansive soils exposed to rainfall and drying.
Please make clear in conclusions that this study provides a numerical method to assess risk of landslides in soil excavations and that the parameters are derived form lab tests. The method is applied for a practical example.
Author Response
Dear Reviewer:
Thank you for the reviewers’ comments concerning our manuscript (ID: water-809314). Your opinion is very important. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in blue in the two part.
Thank you again for your patience and valuable comments.
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
please, find the attached file
Comments for author File: Comments.pdf
Reviewer 2 Report
General comments
In the paper under consideration, the authors present stability analyses of an expansive soil slope from China based on laboratory tests and FEM modelling.
During my revision, I identified some errors in the experimental approach, which effect the entire subsequent simulation and conclusions.
I feel very sorry to reject this submission.
Specific comments
[2.2.1 The process of dry and wet cycle] This section lacks in detail. E.g., “Therefore, 6 sets of soil samples should be prepared, and each 10 soil samples should be used as a group for dry and wet cycles.” This sentence is ambiguous and it is not clear how many samples were tested.
I am not convinced that the methodological approach as presented herein reflects the natural conditions in the soil. It was not explained how the sample was sampled (undisturbed or remolded) and whether or not the sample was placed in a sample mold. These are important information in order to judge about the rationale behind the methodological approach. As it reads, I assume the authors “just” placed the samples between filter stones, while the horizontal areas of the sample were in contact with air. Then the filter upper stone was sprayed with water (and of course the horizontal areas too). In my opinion this does not reflect the natural condition in the soil, where the horizontal part of a soil element is not in direct contact to air and rain, but to surrounding soil. The change of the samples (dimensions, water content) due to this process were not quantified. The drying process does not seems realistic to me. I wonder, why the authors did not use an oedometer apparatus to test the samples in controlled conditions.
[2.2.2 Measurement of strength and permeability coefficient] The entire section lacks in detail. One may not be able to replicate the experiments described. E.g., how did the authors humidified the samples (after wet-dry cycles) to natural moisture conditions?
[2.3 Weathering fracture] The description of crack development is scientifically very poor. I wonder why the authors did not better quantified the crack development within the sample. The authors showed internal cracks in Fig. 5. However, these cracks could be affected or even caused by the way the authors cut their samples in halves (which I know is not easy to quantify).
Technical comments
Language was mostly fine. However, I noticed a large number of typos that were mostly associated with missing spaces between words. Please correct these errors.
