Discrete Fracture Network (DFN) as an Effective Tool to Study the Scale Effects of Rock Quality Designation Measurements

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript is interesting for the reader and is written in correct English

The originality of the text and the novelty of the work are obvious.

The name of the manuscript corresponds to its content, which is laid out quite clearly.

The study is correctly designed.

The results of the calculations are presented in depth and are accompanied by a large number of calculations and graphs.

The conclusions are completely correlated with the obtained results.

There are several wishes for improving the manuscript:

1. 24  of the 35 references presented in the list of sources are 10 years old or older. It would be good to supplement the list of literature with newer sources.

2. For a better understanding of the graphic results, it would be good to present the legends regarding the adopted designations in Figures 5, 6, 7.

3. Perhaps it would be better to expand the curiosity due to the discussion part of manuscript

It would be  worth to improve the list of citations.

The graphic interpretations in Figures 5, 6, 7 are very important for understanding the essence of the research methodology and therefore it is worth presenting them more fully by adding legends of colored symbols.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

In this paper, scale effects for RQD measurements are studied  using synthetic rock masses generated by means of discrete fracture network (DFN) models. RQD  measurements are performed for rock masses with varying fracture intensities and by changing the orientation of the simulated boreholes to account for orientation bias. The objective is to demonstrate the existence of a Representative Elementary Length (REL, 1D analogue of a 3D representative  elementary volume, or REV) above which RQD measurements would represent an average indicator of rock mass quality.

Disadvantages of Using Discrete Fracture Network (DFN) Models to Study Scale Effects on Rock Quality Designation (RQD) Measurements are:

-      DFN modeling is complex and requires significant computational resources;

-      DFN models often involve simplifications and approximations of the actual geological structure;

-      RQD represents only one aspect of rock mass quality and has inherent limitations due to the simplicity of the measurement method. DFN models focus on RQD assessment but may not capture all relevant aspects of rock mass quality, such as the complex mechanical or hydraulic behavior of fractures;

-      the accuracy of the DFN model heavily depends on the quality and quantity of mapped fracture data; incomplete or inaccurate data can lead to unrepresentative models, negatively impacting the results and conclusions drawn;

-      the definition of Representative Elementary Length (REL) and Representative Elementary Volume (REV) is dependent on the specific geotechnical domain and its variability; DFN models applicable in a homogeneous domain may not be relevant for geotechnical domains with significant variations, such as shear or fault zones.

DFN models require validation through comparisons with actual RQD measurements from boreholes. Experimental validation and extending studies to include more complex fracture sets are crucial steps for improving the reliability and applicability of this method. The presented method may be used in this case, but is difficult to use in another case – needs another calibration with experimental results.

I would be grateful if the authors of the article would point out the novelties brought in this analysis compared to the existing information.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

From the point of view of the English language, the article is written correctly, there are some smaller problems with space and pictures resolutions - the necessary corrections were indicated in the attached document.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

General remarks: The authors propose a study aimed at investigating the Discrete Fracture Network (DFN) as a tool to measure the scale effects of Rock Quality Designation (RQD) measurements. Scale effects for RQD measurements are investigated using synthetic rock masses generated using discrete fracture network (DFN) models. The reviewer is of the opinion that a MINOR revision is required. Some responses need to be carried out by the authors to answer the questions Q suggested by the reviewer.

Q1) The uniqueness of the research must be emphasized. What is missing in the context of the results already proposed in the literature that the authors want to address? This description must be included in the paper and not in the reviewer's letter.

Q2) The structure of the paper is confusing. It is recommended that the authors organize the sections of the paper as follows: Introduction, Literature Review (i.e., the state of art), Methods, Results and Conclusion. The paper is very difficult to understand. The ideas are not clear due to the inadequate organization of the paper.

Q3) Section 2, line 82, the authors say “DFN modelling has been widely used in geomechanics applications”. What kind of applications?

Q4) Figures and tables are rarely used in the work's introduction.

Q5) Section 4.1: Please justify the conceptual rock mass generated using the parameters listed in Table 3

Q6) Section 4.1 – Table 4: Why is the difference between the RQD calculated using center well and the average of the four surrounding wells negligible?

Q7) Section 4.1.2 line 172: why do the authors use the orthogonal wells as an example?

Q8) The discussion of figures 7-15 needs to be improved. All figures need to be discussed technically in the paper. The same applies to figures 20-22.

Q9) Section 4.1.2: “The results for the inclined boreholes show a very similar pattern”. Why? Please, improve the description and analysis.

Q10) Figure 23 is impossible to read. Please improve the quality and height of the text.

Comments on the Quality of English Language

None

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have taken my suggestions into account. The novelties brought in this analysis compared to the existing information using the Discrete Fracture Network (DFN) is the possibility to define an equivalent length over which RQD variability decreases significantly. For the primary goal of the study of scale effects, in this work, RQD of different measuring lengths was calculated to determine the scale effects in RQD with varying lengths, which range from 3 to 30 meters. The studies presented in this paper need to be extended to DFN models with more complex fracture sets and to compare actual RQD measurements along boreholes to the simulated RQD values measured in the associated DFN models. The studies presented in this paper confirmed the potential of DFN models for fragmentation determination and evaluation.

In conclusion, this paper can be published in this form after minor revisions (corrections to minor methodological errors and text editing).

Comments for author File: Comments.pdf

Comments on the Quality of English Language

There are some smaller problems with some grammar correction, pictures, the necessary corrections were indicated in the attached document.

Author Response

Agree. We have, accordingly, corrected the errors, and changed images for better illustration.

Author Response File: Author Response.docx