Some Remarks on the Use of Deterministic and Probabilistic Approaches in the Evaluation of Rock Slope Stability
Round 1
Reviewer 1 Report
The paper deals with a comparison of two approaches of rock slope stability explained via two examples from Southern Italy. Deterministic and probabilistic approaches are compared with the analysed slopes using computer codes (RocScience) and Monte Carlo simulations describing planar and wedge failures. The manuscript is overall well written both in linguistic and scientific terms and has clear statements but it needs some reorganization and requires additional data. There are some changes that are suggested, especially in methods and test results part. A more detailed Discussion section is requested and it has to be separated from Conclusions. Parts of the manuscript need to be modified prior to publication.
Overall, it is an interesting paper which is recommended for publications but only after several changes. The main points are listed here and the detailed comments are provided below.
Main points to consider:
- The Materials and Methods section- it would be better to divide the two parts into two separate sessions.
- Methods part: the calculations are described in details, but it is also necessary to provide and describe the laboratory test methods (according to EN or ISRM?) that are used to obtain rock mechanical data. The data were used as input parameters in the modelling.
- Material part: the geological description is given in the ’ Applications of the suggested method’ section. It would be better to remove these descriptions and make a separate section: Geology, which is than would be followed by ’Results’
- The Discussion section requires additional work. It has to be more extended with a comparison of the results with previously published ones. The paper provides a set of references, however, some important papers, especially the recent ones are missing, describing the combined use of computer codes and laboratory tests in rock slope stability assessment.
- Discussion and Conclusions need to be divided into two separated sections.
- An updated list of recently published papers on rock slope stability and wedge and planar failures would be better to refer and cite.
Detailed comments:
P= page, L=Line
P2 L82: ‘In Figure 1, the overall methodology…’ Please do not start a sentence with a reference to Figures or Tables. Pls. rephrase it. (it is common throughout the manuscript)
P2-3. It would be better to explain the methods first (P2 L82-onward) and move Fig. 1. bottom part of the Methodology section.
P5 L146: ‘3. Applications of the suggested method: Case studies’ is not an appropriate heading. I would rather use ‘Results’ and than as subheading ‘Planar failure’ and ‘Wedge failure’
P6 L169-17: Table 1. gamma (s) – ‘absolute unit weight’ is not a proper expression it is called ‘unit weight of solids’ or in rock mechanics, the preferred expression is ‘material density’ (later on P9, Table 2 ‘rock density is used’). Pls. use the term consistently.
P6 Table 1. Pls. calculate the mean values and standard deviation of parameters and provide it here in the table.
P6 L175: Pls. correct: Schmidt hammer rebound and not ‘Schmidt rebound hammer’ Can you provide data/values of Schmidt hammer rebound?
P9 L 253-254: In Table 2 standard deviation of ‘rock density’ is given under the symbol of small sigma. Can you reshape the table, it looks a bit strange. Compare it with Table 3 P11, where no such value is given.
P11 L302: ‘In Figure 10…’ Please do not start a sentence with a reference to Figures or Tables. Pls. rephrase it.
P12 L319-P13 L369: IMPORTANT! The Discussion needs to be separated from Conclusions. A more detailed discussion of the results and a comparison of the results with previously published similar research is required. Comparison with some important findings published in more recent papers is missing. The mechanical parameters of rocks, the shear strenght values and their role in deterministic and probabilistic slope analyses have to be explained.
A Conclusion is missing with remarks on the importance of the analyses and the outcomes of the research! It is only partly given in the last section, now.
P14-15. Additional references are required here to provide a better overview of the previous research achievements of other authors.
Author Response
The Materials and Methods section - it would be better to divide the two parts into two separate sessions.
Methods part: …………….
Material part: …………………
According to the reviewer’s suggestions, in the text all headings were rephrased and conveniently split in subsections. Furthermore, a new section ‘Geological setting’ was added. The paragraph ‘Discussion and Conclusions’ was also split in two separate sections.
P2 L82: ‘In Figure 1, the overall methodology…’ Please do not start a sentence with a reference to Figures or Tables. Pls. rephrase it. (it is common throughout the manuscript).
All sentences starting with references to Figures and Tables were rephrased.
P2-3. It would be better to explain the methods first (P2 L82-onward) and move Fig. 1. bottom part of the Methodology section.
In the text, this suggestion was conveniently implemented.
P5 L146: ‘3. Applications of the suggested method: Case studies’ is not an appropriate heading. I would rather use ‘Results’ and than as subheading ‘Planar failure’ and ‘Wedge failure’.
According to the reviewer’s suggestion, all headings were rephrased and conveniently split in subsections.
P6 L169-17: Table 1. gamma (s) – ‘absolute unit weight’ is not a proper expression it is called ‘unit weight of solids’ or in rock mechanics, the preferred expression is ‘material density’ (later on P9, Table 2 ‘rock density is used’). Pls. use the term consistently.
The term ‘absolute unit weight’ was replaced with ‘material density’. Through the whole text, the term ‘unit weight of the rock’ replaced the ‘rock density’ one.
P6 Table 1. Pls. calculate the mean values and standard deviation of parameters and provide it here in the table.
This data was calculated and provided in the table.
P6 L175: Pls. correct: Schmidt hammer rebound and not ‘Schmidt rebound hammer’ Can you provide data/values of Schmidt hammer rebound?
According to the reviewer’s suggestion, the corrections were implemented.
P9 L 253-254: In Table 2 standard deviation of ‘rock density’ is given under the symbol of small sigma. Can you reshape the table, it looks a bit strange. Compare it with Table 3 P11, where no such value is given.
Tables 2 and 3 were redrawn. In order to simplify these tables, all geometrical and physical data of the adopted models were moved in the text.
P11 L302: ‘In Figure 10…’ Please do not start a sentence with a reference to Figures or Tables. Pls. rephrase it. Please see my previous reply concerning P2 L82
P12 L319-P13 L369: IMPORTANT! The Discussion needs to be separated from Conclusions. A more detailed discussion of the results and a comparison of the results with previously published similar research is required. Comparison with some important findings published in more recent papers is missing. The mechanical parameters of rocks, the shear strength values and their role in deterministic and probabilistic slope analyses have to be explained.
According to the reviewer’s suggestion, the Discussion and Conclusion paragraph was split in two separate paragraphs. Further findings concerning geomechanical parameters as well deterministic and probabilistic slope analyses published in more recent papers were added (please see on page 14, lines 368-374).
A Conclusion is missing with remarks on the importance of the analyses and the outcomes of the research! It is only partly given in the last section, now.
The paragraph Conclusions was completely rewritten.
P14-15. Additional references are required here to provide a better overview of the previous research achievements of other authors.
News references were added on page 16.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Please specifically mention the aim of the study and how to improve the slope stability analysis. Novelty procedure or contribution.
The Methods have been used should be clearly integrated.
The results needs to be more comprehensive.
The conclusion section needs to be improved.
Comments for author File: 
Comments.pdf
Author Response
The Methods have been used should be clearly integrated.
In order to answer that question, the entire text was revised and rewritten.
The results needs to be more comprehensive.
According to the reviewer’s suggestion, in the paragraph Discussion a more comprehensive description of the obtained results was added.
The conclusion section needs to be improved. The paragraph Conclusions was completely rewritten.
Further corrections suggested in the pdf file.
P1L6. The affiliation has been translated in English.
P1L25. Limit equilibrium.
P1L40-41. A critical review of these approaches and their pros and cons advantages is attributable to [2, 3].
P2L54. According to [9], the…
P2L71. Probability of failure (Pf).
P3Figure 1. The suggested adjustments have made.
P3L95-96. Peak friction angles (?p), obtained by means of shear tests on natural joint surfaces, for which is already considered the effect of waviness angle, were used.
P3L102-103. Where the angles beta and epsilon are measured on the cyclographic projection showing the great circle containing the pole to the line of intersection and the poles of the two slide planes, respectively.
P5L145. Since no joint infilling and continuous groundwater circulation……
P6 Table 1. The data comes from slope 1 or 2? In the new text (L173): …the dolomitic limestones sampled in the two studied sites.
P6Figure3. The suggested adjustment has made
P6L184-186. According to [7], for reducing……
P7Figure 5. Key: symbol tetap (4)
P8L237. 17÷46 = 0.369
P9Table 2. Tables 2 and 3 were redrawn. In order to simplify these tables, all geometrical and physical data of the adopted models were moved in the text.
P10L289. 205÷884 = 0.231
Author Response File: Author Response.pdf
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
The manuscript entitled “Some remarks on the use of deterministic and probabilistic approaches in the evaluation of rock slope stability” deals with the stability analysis of two rock slopes by kinematic, deterministic and probabilistic analyses with the aim of comparing results and calculating the conditional probability of rock failure.
Although the topic might be interesting, no scientific novelty is provided in this study. The scientific purpose of the research, along with its utility for the international Scientific Community, are not well defined.
The manuscript looks more like a master’s degree thesis or a stability analysis exercise, rather than a scientific article. Furthermore, the text is affected by some grammatical errors, which would require a revision of written English, possibly by a native speaker. According to these considerations and to the main following comments, I believe the manuscript is not suitable for publication in the present form.
My main comments are referred to the following points:
There is a poor bibliographic research, especially to highlight some practical case studies employing such approaches. The manuscript contains a long theoretical part, whose shortening would be welcomed in a scientific paper. This manuscript is not aimed at being a textbook! A more detailed geological-geomechanical description of the studied slopes, as well as some more field photos, would have been welcomed, especially because results and computations arise from field data and the readership maybe has never been in such places. Same for laboratory tests: the Author claims to have carried out laboratory tests to estimate the shear strength of clean rock joints and the physical properties of the rock. Some photos of the laboratory setting and specimens would have been welcomed. The Author wrote that rock specimens containing natural joint surfaces were tested by Hoek’s shear box. How did the Author estimate the value of the basic friction angle? Did he use some other specimens with man-made joints? The choice of 30° should have been motivated and supported. With reference to laboratory tests, how did the Author estimate the rock density? The reference of international specifications should have been added. In fig. 5, the lateral limits for the planar kinematic analysis should have been added. Table 2: The Author should have provided some more indication on the choice of minimum and maximum values. I suppose he used the software Dips to this purpose. How about the standard deviation? Did the Author took into account the Fisher Distribution? If yes, what value of variability limit did he consider? All these indications should have been reported. Figure 8: the figure style is different with respect to fig. 5. A unique style of representing stereographic projection should have been chosen. Table 3: friction angle values are the same employed for the analysis of the other outcrop. How can they be considered representative of both rock masses? From the geological map is evident that the two study sites are not close. This looks like an approximation of the use of field data. Furthermore, the Author should motivate why friction angle was considered herein equal for J1 and J2. Swedge software gives the opportunity to differentiate such values; this choice should have been motivated.
Best Regards
Reviewer 2 Report
The paper reports an analysis of rock slope stability in southern Italy. In general, the paper is well written and the figures are good. The approach is not novel, and the case study very simple. However, the paper has the merit to present and compare three methods that are usually applied in Engineering geology, and to show the difference among these three methods. Although I would not recommend the publication on a specific “engineering geology” journal, I believe that the manuscript is appropriate for Geosciences, expecting the audience to be more generalist with respect to other journals. Therefore, I suggest accepting the paper with moderate revisions.
Abstract. The abstract describes the deterministic methods but oversimplify the point, by mentioning only to kinematic approaches (usually carried out…). As reported in the introduction, deterministic methods include much more advanced stability methods (LEM and numerical). I suggest to rephrase the sentence in the abstract.
Methods. The calculation of the overall probability by combining the kinematic and the kinetic probabilities requires independency of the two probabilities. This assumption is not proved nor discussed. I hardly understand how they can be independent. If one of the two is large, the other is probably large. Moreover, I’m not convinced that the combination of the two probabilities is a real advantage. In the kinetic approach the orientations of the joints are stochastically changed. This imply that the resulting probability already includes the fact that some orientations are not kinematically feasible (the SF would be high). Hence, the further multiplication of the failure probability (kinetic) with the kinematic one looks a redundancy in my mind.
I may be wrong, but I expect the author to discuss this points (independency and redundancy) in the paper, also because the resulting probability is much smaller. This is totally non-conservative.
Figure 2. Add the meaning of PF and WF in the caption.
Chapter 2.2 describe here the meaning of the probability of failure (number of unstable kinematisms/tot. number of kinematism) and how this value can be compared to the others.
Discussion. This section should be significantly improved. Considering that the method is not innovative and that the case study is very simple and not particularly interesting (as case study), the author should try to deepen the meaning of the different methods, trying to discuss advantages and limits of all of them, also considering the point suggested above about independency and redundancy.
