Brief Literature Review and Classification System of Reliability Methods for Evaluating the Stability of Earth Slopes
Round 1
Reviewer 1 Report
Review Comments on Manuscript entitled "Brief Literature Review and Classification System of Reliability Methods for Evaluating the Stability of Earth Slopes"(sustainability-1331769)：
Please consider the following points during the revision of the manuscript:
What is the practical meaning of the classification system?
How do engineers apply this classification system solve real slope problems?
It is recommended that a more precise description be made in the appropriate place.
Author Response
What is the practical meaning of the classification system?
This is a very good question and one that I have pondered at times myself. This question could be generalized to any classification system in any discipline. On the one hand, one could say that classification systems have no practical relevance, at least in a direct sense. However, on the other hand, in practical applications it is mainly important to choose the right method for a particular problem. And this is where a classification system can come in handy. In addition, the classification system allows to organize many methods and thus better understand and assimilate them. In this view, its impact on practice would have to be considered indirect. The paper mentions that there is a classification system of reliability methods for rock slope assessment (with modifications). In the world literature much more publications deal with earth slopes, more methods have been developed here and there is no classification system. Hence it seemed expedient to fill this gap.
How do engineers apply this classification system solve real slope problems?
The proposed system should help the engineer to select an appropriate method for reliability assessment of a particular slope under consideration. The method will depend on the nature of the slope, the available parameters and statistics, the required computational accuracy or the software the engineer has at his disposal. For example, for a simple slope of little practical significance, it is reasonable to use SRVLEM1 or SRVLEM2 methods. On the other hand, for slopes of complex geological structure, posing a threat to the population or infrastructure, REFEM3 should be used. Of course, the system alone is not enough. Knowledge of reliability theory and available software is also essential here. Unfortunately, reliability methods for slope stability assessment are still not very often used in practice, which is due to many reasons. However, it seems that they will be used more and more often with the development of appropriate software and also statistical geotechnical database. Then the proposed system should be more beneficial.
It is recommended that a more precise description be made in the appropriate place.
Unfortunately, the Reviewer did not indicate the appropriate place where more precise description should have been made.
Review 1
What is the practical meaning of the classification system?
This is a very good question and one that I have pondered at times myself. This question could be generalized to any classification system in any discipline. On the one hand, one could say that classification systems have no practical relevance, at least in a direct sense. However, on the other hand, in practical applications it is mainly important to choose the right method for a particular problem. And this is where a classification system can come in handy. In addition, the classification system allows to organize many methods and thus better understand and assimilate them. In this view, its impact on practice would have to be considered indirect. The paper mentions that there is a classification system of reliability methods for rock slope assessment (with modifications). In the world literature much more publications deal with earth slopes, more methods have been developed here and there is no classification system. Hence it seemed expedient to fill this gap.
How do engineers apply this classification system solve real slope problems?
The proposed system should help the engineer to select an appropriate method for reliability assessment of a particular slope under consideration. The method will depend on the nature of the slope, the available parameters and statistics, the required computational accuracy or the software the engineer has at his disposal. For example, for a simple slope of little practical significance, it is reasonable to use SRVLEM1 or SRVLEM2 methods. On the other hand, for slopes of complex geological structure, posing a threat to the population or infrastructure, REFEM3 should be used. Of course, the system alone is not enough. Knowledge of reliability theory and available software is also essential here. Unfortunately, reliability methods for slope stability assessment are still not very often used in practice, which is due to many reasons. However, it seems that they will be used more and more often with the development of appropriate software and also statistical geotechnical database. Then the proposed system should be more beneficial.
It is recommended that a more precise description be made in the appropriate place.
Unfortunately, the Reviewer did not indicate the appropriate place where more precise description should have been made.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
General Comments:
Dear Researcher,
Thank you very much for the interesting article, however, I would like to see a future work more complete, including more references as you already mention in your last paragraph of the article.
After reading your work, I would like to point out some comments:
Line 21-25, please include reference.
Line 125-27, please include reference.
Line 128- 129, “Regardless, it appears that these methods fall within the reliability method classification system proposed in the paper.”
Please explain briefly, which methods fall within the proposed method.
Line 329-331, “There are too few papers presenting application of the reliability approach in a comprehensible and simple way.” Please include reference.
Line 464-467, “The environmental impacts were also ignored, i.e. caused by earthquakes, excessive precipitation or temperature changes. However, it seems that the reliability methods of slope stability analysis used in these cases are included in the proposed computing classification system “.
Please explain why these impacts were not mentioned in your current research and present us the importance of these impacts in the proposed classification system.
Author Response
Line 21-25, please include reference.
I am a co-author of probably the world's first monograph on probabilistic slope stability assessment, unfortunately written in Polish and published in 1990. Since then, I have systematically studied the literature on this subject, participated in numerous conferences, discussions. The sentence “last dozen years or so, in the leading geological and geotechnical journals, as well as proceedings summarising international conferences, several thousand publications have appeared on this subject” is based on my experience and analysis of an extensive literature, only a small part of which I have quoted in this paper.
Line 125-27, please include reference.
In accordance with the Reviewer’s comment, several references has been added in the revised paper.
Line 128- 129, “Regardless, it appears that these methods fall within the reliability method classification system proposed in the paper.”
Please explain briefly, which methods fall within the proposed method.
I am grateful to the Reviewer for the remark. The proposed system is based on three elements: soil description method, reliability level and deterministic method. The common methods for slope stability analyses in a seismic zone include: pseudo-static analysis, Newmark displacement analysis and dynamic numerical analysis. Pseudo-static stability analysis is a widely used limit equilibrium method that replaces the effect of dynamic earthquake loads by a constant equivalent-static acceleration. Also, Newmark's method can be classified as the LEM. Dynamic analysis is usually performed with the finite element or finite difference method. The vast majority if not all of the methods for assessing slope reliability for seismic issues are essentially only concerned with the former two. Certainty the pseudo-static methods fall within the proposed system. The same goes for environmental burdens. For example, the method proposed by Chiu et al. (2012) can be denoted as SRLEM2, while the method proposed by Zhang et al. (2005) denoted as RFEM3.
Line 329-331, “There are too few papers presenting application of the reliability approach in a comprehensible and simple way.” Please include reference.
These papers are listed in the next paragraph, starting with Low and Tang (1997, 2007), Low et al. (1998), El-Ramly et al. (2002), etc. I believe that both the former and the other papers mentioned in the paragraph are written in a comprehensible and simple way.
Line 464-467, “The environmental impacts were also ignored, i.e. caused by earthquakes, excessive precipitation or temperature changes. However, it seems that the reliability methods of slope stability analysis used in these cases are included in the proposed computing classification system “.
Please explain why these impacts were not mentioned in your current research and present us the importance of these impacts in the proposed classification system.
The main objective of the paper was to propose a classification system of methods for evaluating the reliability of earth slopes. An indispensable issue here was a discussion of the criteria for division and a presentation of the different methods. It is difficult to immediately propose a one-size-fits-all system. Already in the title of the paper, the restriction is introduced: “Brief Literature Review. . .” instead of “Literature Rewiev…” or “State of the Art..”. Currently, vast majority of literature on slope stability mainly focus on the reliability of the slope under the static condition. Publications considering earthquake loads are also an important group. Unfortunately, little research has been devoted to environmental loads. In my region (Northern Europe), seismic loads are not present. Also, problems with environmental impacts such as heavy rainfall or temperature changes do not occur. However, in accordance with the Reviewer's remark, several references of these impacts have been added in the revised paper.
Author Response File: Author Response.pdf
Reviewer 3 Report
The draft of “Brief literature review and classification system…earth slopes” reviewed the reliability methods for the earth slope stabilities. It is interesting and new. However, the following unclear parts must be clarified.
- Line 137, “This method is a conceptually simple tool for reliability….”, additional statements should be added to clarify the “conceptually simple tool”.
- Line 143, “that the proposed approach performs”, additional statements must be added to clarify the “proposed approach performs”.
- Line 162, “such as subset simulation (SS), importance sampling (IS)”, references must be added to the SS and IS.
- Add a table to clarify the advantages and disadvantage of different reliability analysis methods to help readers have better understand on it.
- Line 462, “Certainly, a number of publication unavailable to him have”, what dos “him” mean here?
- The following article seems used different approaches of reliability analysis on the slope stability along a mountain highway. The authors should cite and discuss about it.
- Slope management criteria for Alishan Highway based on database of heavy rainfall-induced slope failures, Engineering Geology. 162, p. 97-107.
Author Response
Line 143, “that the proposed approach performs”, additional statements must be added to clarify the “proposed approach performs”.
The proposed approach introduces adaptivity in finite element limit analysis for probabilistic stability applications. It was applied to a two-layered soil slope. Research explores the benefits of combining adaptive mesh refinement with finite element limit analysis for probabilistic applications. The outcomes indicate that in order to achieve tight bounds on probabilistic results (such as the probability of failure), the ultimate load in each individual simulation (e.g. factor of safety) has to be estimated with a very high level of accuracy and this can be achieved more economically using adaptive mesh refinement. The term “proposed approach performs” was cited by the authors (Ali et al. 2017).
- Line 162, “such as subset simulation (SS), importance sampling (IS)”, references must be added to the SS and IS.
References to these publications are included in the article and they are cited three lines below.
- Add a table to clarify the advantages and disadvantage of different reliability analysis methods to help readers have better understand on it.
I agree with this Reviewer's comment. Such a table would certainly improve the value of the article. However, its primary objective was to propose a classification system of methods for assessing the reliability of earth slopes, and to do this it was only necessary to review these methods. Already in the title of the paper, the restriction is introduced: “Brief Literature Review. . .” instead of “Literature Rewiev…” or “State of the Art..Comparison…”. Thorough and appropriate development of such a table is not a simple matter. This is primarily due to the great number of reliability methods (and then there are the hybrid methods). However, it seems more important to elaborate the advantages and disadvantages of particular methods in relation to particular geotechnical conditions, the importance of the object or the required degree of accuracy (level of reliability). Theoretically, methods that have many disadvantages, for specific cases, can give comparable results to much better ones and vice versa. Unfortunately, I am unable to prepare such a table, especially having a few days to revise the article taking into account the three Reviewers' comments and prepare a response for them. I wouldn't want to do such a table "just any way" which would probably be even worse than not having one. Indeed, in the paper, when discussing the different methods, for most of them the advantages and disadvantages are described.
- Line 462, “Certainly, a number of publication unavailable to him have”, what dos “him” mean here?
Unfortunately, not all journals are available in the library at my University (there is no Geological Department also there is Civil Engineering Dept.). An example is the lack of access to an important journal like Engineering Geology. The process of importing them is not easy and often very time consuming. The same goes for conference materials. There have been times when I have not been able to get some publications. In many cases, the only option was to read the summary available online.
- The following article seems used different approaches of reliability analysis on the slope stability along a mountain highway. The authors should cite and discuss about it.
- Slope management criteria for Alishan Highway based on database of heavy rainfall-induced slope failures, Engineering Geology. 162, p. 97-107.
Unfortunately, this article is unavailable to me. I have also asked for its authors to be sent to ResearchGate but so far without success. However, the article was placed in the references and cited.
Author Response File: Author Response.pdf
