Different Stress Paths Lead to Different Failure Envelopes: Impact on Rock Characterisation and Design

Round 1

Reviewer 1 Report

-The abstract seems to be confusing, generally the abstract should contain several parts such as the significance of the study, methodology, results and analysis, but some key issues especially explicit conclusion do not appear in the abstract, which, I think, needs to be reworked.

-Too many fragmented statements and colloquial expressions that largely affect the rigor and readability of the paper, such as line51 “and the next step is...”, line56 “From a practical point of view...”, line58 “as is well known...”, line60 “and, possibly, even...”. Please review the entire manuscript and improve the writing.

-The use of terms and their abbreviations is confusing. Typically, the first occurrence of the term should be in all caps, and its abbreviation may be used in subsequent occurrences, or it should be consistent throughout the whole manuscript. Check line 34 for moduli, UCS, and BTS, and line 42 Brazilian tensile tests, uniaxial or unconfined compression tests, and conventional triaxial tests. 

-Check line 38-line 41, its value is influenced 1) by... 2)by...3)by... 4)...,This style of writing is not conducive to a better understanding of what the author is trying to convey.

-Check “ The recording of acoustic emission is hereby a useful tool (e.g., [8, 30-42]).” in line 194,”or in mixed mode (e.g., [31, 43-47])” in line 196, “micro-photographs of petrographic thin sections or of fracture surfaces (e.g., [2, 10, 22, 48-49]), SEM micrographs (e.g., [14, 26, 28, 35, 40-43, 49-51]), reflection microscopy images (e.g., [49]) and (micro-)CT images (e.g., [2, 11, 28, 35, 52-55])” in line 199-201.Why so much literature against in simple sentences with several , more details of methods and clear conclusions need to be shown.

-Check line98 “(See further for more details on the code and model.)”, it’s hard to understand ,show more details about the code and model.

-Check if line 118 "...by an unloading". It seems that some of the sentence is missing.

-Check line112 “As mentioned earlier, the knowledge of unloading stress paths that occur around excavations is not new.”. Such a statement is meaningless and is something that needs to be argued and explained in detail, and needs to be supported by more literature.

-Macro-fractures (line 123) need to be defined first, especially the difference from micro-fractures or  individual fractures needs to be clarified, as well as the basis of how to determine if macro-fractures has been created besides “the UCS values also were systematically lower”.

-“2. Overview of unloading experiments” should not occupy so much space, attention should be paid to the key points of the research, more focused on the focus of the study, if these contents (line111-line236) are only a simple overview, then the separate chapter is meaningless, integration and streamlining of these into the “1.introduction”, as the background of the whole study is more appropriate.

-Who does “WE” refer to here in “As shown in the paper this article has only one author” line254 “we have used with success in the past the two-dimensional Universal Distinct Element Code (UDEC)”.

- In order to have a better understanding “RVE of the black box rock in this study referred to the distinct element UDEC model” in line 237- line 335. more work needs to be done.

-Is it reasonable and convincing to rely entirely on reference 28 (Song, Z. et, al.) for “5. Comparison between RVE model and published laboratory experiments” in line 586- line 722.

 -The conclusions need to be reorganized; the process of exposition and comparative analysis has already been completed in the study, and references do not need to and should not reappear in conclusions.

Please review the entire manuscript and improve the writing, Extensive editing of English language required.

Author Response

Dear editors and reviewers,

First of all, I would like to thank you for your time reviewing my submitted paper and for formulating useful and relevant comments, which helped me to improve the manuscript.

In the attached document, I address each individual comment or suggestion per reviewer. However, there are two issues where your comments differ:

• First, the relevance of all references. One of you consider them to be all relevant, while two of you make the remark that it can or must, respectively, be improved. The remark mainly refers to the lab observations and measurements of micro- and macro-fracturing. After further reflection, I decided to keep all references. The reason for this decision is that the crucial aspect in the study is the occurrence of micro- and macro-fractures, and this in-situ, in lab experiments and in the numerical model. Although the paper concentrates on numerical simulations and on the occurrence of (micro-)fractures, it is important that it is clearly stated that the latter are also observed and measured in-situ and in lab experiments. I assume that some of the readers of the journal Applied Sciences are not familiar with these measurements. And, thus, I have kept the references. In fact, the insights that my research team gained in the understanding of failure are in first instance based on the measurements; the discrete element simulations came only afterwards.
• Second, the quality of the English language. Again, the classification varies between no issues, and minor and extensive editing is needed. All the specific suggestions for improvement were applied to the new version of the manuscript. However, the original manuscript was in detail and thoroughly edited by a professional editor, i.e., someone born in the UK and with an engineering background, and operating within the framework of Servicescape. Since 2014, all my published papers were edited by the same professional, and this to the satisfaction of the various journals.

I hope that you are satisfied with the changes made, following your comments, and that the new version of the paper will be accepted for publication. Thanks again for all your effort.

Kind regards,

Prof. André Vervoort

Author Response File: Author Response.pdf

Reviewer 2 Report

In this manuscript, the effect of the stress path on the failure envelope is studied using the distinct element code UDEC. After a careful reading of the manuscript, the following questions need to be resolved:

1. The conclusion is too long and needs to be streamlined.

2. In the model, the author mentioned that 273 units are used, is that too few? Please clarify.

3. What are the criteria for crack initiation and propagation in the model? Please specify.

4. In the model, the initial values of parameters and boundary Settings need to be described in detail.

5. In the comparison of simulation results and experimental results, it is strongly recommended that the author use the form of graphs or tables to enhance readability.

The full name and abbreviation of REV appear many times, please check carefully. Also ask the author to check for other grammar problems.

Author Response

Dear editors and reviewers,

First of all, I would like to thank you for your time reviewing my submitted paper and for formulating useful and relevant comments, which helped me to improve the manuscript.

In the attached document, I address each individual comment or suggestion per reviewer. However, there are two issues where your comments differ:

• First, the relevance of all references. One of you consider them to be all relevant, while two of you make the remark that it can or must, respectively, be improved. The remark mainly refers to the lab observations and measurements of micro- and macro-fracturing. After further reflection, I decided to keep all references. The reason for this decision is that the crucial aspect in the study is the occurrence of micro- and macro-fractures, and this in-situ, in lab experiments and in the numerical model. Although the paper concentrates on numerical simulations and on the occurrence of (micro-)fractures, it is important that it is clearly stated that the latter are also observed and measured in-situ and in lab experiments. I assume that some of the readers of the journal Applied Sciences are not familiar with these measurements. And, thus, I have kept the references. In fact, the insights that my research team gained in the understanding of failure are in first instance based on the measurements; the discrete element simulations came only afterwards.
• Second, the quality of the English language. Again, the classification varies between no issues, and minor and extensive editing is needed. All the specific suggestions for improvement were applied to the new version of the manuscript. However, the original manuscript was in detail and thoroughly edited by a professional editor, i.e., someone born in the UK and with an engineering background, and operating within the framework of Servicescape. Since 2014, all my published papers were edited by the same professional, and this to the satisfaction of the various journals.

I hope that you are satisfied with the changes made, following your comments, and that the new version of the paper will be accepted for publication. Thanks again for all your effort.

Kind regards,

Prof. André Vervoort

Author Response File: Author Response.pdf

Reviewer 3 Report

The authors performed numerical simulations using small Representative Volume Element (RVE) under different stress paths and analyzed the results in detail. The manuscript is well written and clearly states the objectives to study the effect of different stress paths instead of simulating entire samples under lab or real world conditions. The study finds that the rock strength is changing under different stress paths which are supported by the simulation results and the micro fracturing plays an important role in the failure process. The results are also compared to the lab experiment and the consistency shows the potential of RVE simulations.

 

Here are a few minor comments,

 

Figure 1: please explain the blue and red arrows

Figure 4: please explain the short forms of “loa”, “=”, and “unl” in caption

Author Response

Dear editors and reviewers,

First of all, I would like to thank you for your time reviewing my submitted paper and for formulating useful and relevant comments, which helped me to improve the manuscript.

In the attached document, I address each individual comment or suggestion per reviewer. However, there are two issues where your comments differ:

• First, the relevance of all references. One of you consider them to be all relevant, while two of you make the remark that it can or must, respectively, be improved. The remark mainly refers to the lab observations and measurements of micro- and macro-fracturing. After further reflection, I decided to keep all references. The reason for this decision is that the crucial aspect in the study is the occurrence of micro- and macro-fractures, and this in-situ, in lab experiments and in the numerical model. Although the paper concentrates on numerical simulations and on the occurrence of (micro-)fractures, it is important that it is clearly stated that the latter are also observed and measured in-situ and in lab experiments. I assume that some of the readers of the journal Applied Sciences are not familiar with these measurements. And, thus, I have kept the references. In fact, the insights that my research team gained in the understanding of failure are in first instance based on the measurements; the discrete element simulations came only afterwards.
• Second, the quality of the English language. Again, the classification varies between no issues, and minor and extensive editing is needed. All the specific suggestions for improvement were applied to the new version of the manuscript. However, the original manuscript was in detail and thoroughly edited by a professional editor, i.e., someone born in the UK and with an engineering background, and operating within the framework of Servicescape. Since 2014, all my published papers were edited by the same professional, and this to the satisfaction of the various journals.

I hope that you are satisfied with the changes made, following your comments, and that the new version of the paper will be accepted for publication. Thanks again for all your effort.

Kind regards,

Prof. André Vervoort

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

I have no further questions.