Stability Analysis of Embankment Slope Considering Water Absorption and Softening of Subgrade Expansive Soil
Round 1
Reviewer 1 Report
It could be concluded that the topic choice in this paper is of practical significance, the technical route is correct, the experimental data are credible, and the research results have certain reference values.
Agree with publication after the following revisions.
1- The abstract needs serious rewriting. At the beginning of the abstract, remove the extra sentences and clearly state the purpose of the research.
2- Findings should also be clearly presented in the abstract.
3- Please use more relevant references to enrich the literature review section. for example:
"DOI: 10.1088/1755-1315/570/3/032022"
4- Before a figure or table is shown, it must be referenced in the text, please check all.
5- Line 184: which figure??? Please specify the figure number.
6- Line 202, "The depth and distribution range are shown in the figure, and the parameter….." which figure??? Please specify the figure number. Please check all.
7- In the conclusions, it is suggested that some important highlights and application prospects, as well as existed problems should be specified.
8- In order to see the results better, it is suggested to provide a regular summary of the findings in a table.
Author Response
Thank you for your patience and valuable suggestions. All your suggestions are very important.
I am very sorry for these mistakes in the paper. First, we reorganized and rewrote the summary, and revised the ending and corresponding chapters.I rechecked the chart numbers and checked the citations in the paper. At the same time, I modified other questions you raised. Thank you again for your patient and meticulous review. Please criticize and correct. We look forward to receiving your valuable comments.
Reviewer 2 Report
This paper investigates the stability issue of slopes with expansive soils subjected to infiltration of water. The softening effect due to moisture absorption is studied. A FORTRAN-based algorithm is developed for evaluating slope stability. Reinforcement applying to stabilize slopes on this kind of soft expansive soil foundation is proposed. This work is of interest to designers for slope stabilization project. The main comments are as follows.
1. There have been extensive studies on the softening effect of expansive soil slopes. The introduction section does not actually clarify the novelty of this work, including the urgent need to develop a algorithm for calculation, instead of using current commercial programs which can be expected to more mature. Please revise the text to clarify this point.
2. The moisture absorption weakens the expansive soil strength. This is true. In the life of a slope, it is expected to subject many times of wetting-drying cycles. How are the wetting-drying cycles affecting the slope stability, as compared to one individual moisture absorption? Please elaborate.
3. It is unclear how the fissures affect the transportation of water into the expansive soils in the algorithm developed by the authors. These fissures form channels that would dominate the infiltration process, while the seepage through soil pores is secondary. Please elaborate the treatment of this in the algorithm。
Author Response
Thank you for your patience and valuable suggestions. All your suggestions are very important. They have important guiding significance for my thesis and scientific research.
（1）At present, with the rapid development of computer technology and mechanical program, a large number of successful geotechnical engineering software have been formed. These software can consider many mechanical states of soil, such as complex seepage, thermal expansion and dynamic characteristics. Generally, the strength of soil is calculated automatically by the change of soil-water characteristic curve and matrix suction in the software, which is more suitable for common clayey soil. Due to the high clay content of expansive soil, the moisture absorption softening of expansive soil is more obvious and violent than that of common clayey soil. With the difference of clay content, the moisture absorption and softening characteristics of different expansive soils are also quite different. Therefore, the applicability of the above methods is limited. It is necessary to explore a method that is simple to use and easy to obtain parameters in engineering.
（2）For the newly excavated expansive soil slope, the influence of dry and wet cycles is the most important, which is the main factor leading to slope instability. Generally speaking, the strength of expansive soil after more than 5 cycles of drying and wetting can be considered as having declined to stability. However, for the expansive soil layer exposed to the air for a long time and with gentle slope, the surface is in the form of reticulate fracture, which can be considered that the strength has been stable.
（3）Obviously, the soft fracture layer with high permeability is the main infiltration channel of water flow, and the low permeability expansive soil layer on both sides also has seepage. The overall seepage movement is relatively complex, which is difficult to consider comprehensively. According to the field survey and drilling observation during the supplementary landslide survey, the structure of the highly permeable fracture layer is extremely broken, with high water content. Therefore, the soft interlayer with lower strength and higher water content is specified in advance before analysis and calculation.This is a simplified method, and your comments will be the focus of our next research.
At the same time, the corresponding chapters of the paper have been revised.Thank you again for your careful review and look forward to receiving your reply.
Reviewer 3 Report
The topic of article is very interesting, especially in the current context of climate change. However, there are still some problems, and it is recommended that the author make appropriate modifications.
1. The authors state that they have developed a Fortran language program by which they performed the simulations discussed through the tests. However, the paper lacks a detailed description of the process, and it is suggested to supplement or provide corresponding references.
2. Authors should add some detailed information on the measurement of samples with different humidity, which will help readers to replicate the experiments described. For example, how did the authors get so many samples of varying humidity through humidification or drying? How do you know the sample has been humidified to the desired humidity?
3. I noticed that the analysis time of the rainfall process is very long, which is about several months. Yunnan has strong evaporation, especially in the rainy season. The effect of surface evaporation is non-negligible and does not seem to be well considered in this paper.
Author Response
Thank you for your patience and valuable suggestions. All your suggestions are very important. They have important guiding significance for my thesis and scientific research.
（1）The stress-strain relationship of expansive soil is very complex, so far there is no one constitutive model of expansive soil that can fully and accurately express all the characteristics of expansive soil. The essential difference between expansive soil and other soil is its unique expansibility. Therefore, how to reflect the expansibility reasonably and accurately in numerical calculation is a difficulty.
Among all the expansive soil models, the most famous one is the Barcelona expansion model (BExM) proposed by Alonso et al. Based on the triaxial test of unsaturated soil, the model objectively expresses the mechanical properties of unsaturated soil. However, the model is too complex and involves too many parameters, which need to be determined by a large number of unsaturated triaxial tests and isobaric consolidation tests under the condition of controlled suction. All these restrict the application of the model in engineering.
Based on this, some scholars proposed to consider the special properties of expansive soil through the development of subprograms and the relevant functions of commercial software. In this paper, the strength of soil changes with humidity automatically through the development of USFLD subroutine, thus taking into account the moisture absorption and softening of expansive soil.
（2）In the operation part from humidification to natural humidity, the weighing method is adopted. The operation steps are as follows:
1) Measure the mass of the sample first, mark the sample and record the weight of the sample.
2) The test quality is measured continuously during humidification.
3) When the mass increases to the origin mass of soil sample, the humidification shall be stopped.
Round 2
Reviewer 2 Report
The authors have addressed all my comments sufficiently. I thus recommend accept of it.
