Multiscale effects caused by the fracturing and fragmentation of rock blocks during rock mass movement: implications for rock avalanche propagation

Lin, Qiwen; Wang, Yufeng; Xie, Yu; Cheng, Qiangong; Deng, Kaifeng

doi:https://doi.org/10.5194/nhess-22-639-2022

Articles | Volume 22, issue 2

https://doi.org/10.5194/nhess-22-639-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/nhess-22-639-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 22, issue 2

Research article

|

28 Feb 2022

Research article |

| 28 Feb 2022

Multiscale effects caused by the fracturing and fragmentation of rock blocks during rock mass movement: implications for rock avalanche propagation

Qiwen Lin, Yufeng Wang, Yu Xie, Qiangong Cheng, and Kaifeng Deng

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Final revised paper (published on 28 Feb 2022)
Preprint (discussion started on 07 May 2021)

Interactive discussion

Status: closed

RC1:
'Comment on nhess-2021-127', Anonymous Referee #1, 20 May 2021

Dear Authors,

Thank you for interesting paper. I made several comments and suggest some minor corrections listed hereafter:

Line 65. fracturing and fragmentation. fracture means object while you are talking about the process.

Lines 86-89. It will be good to add some comments, explaining how fractal grain-size distribution is related to hypermobility. Any grain-size distribution is what we measure afterward. Why it appear to be this or that is another question.

Line 150. For the traveling path, the inclined plane is a frictionless rigid one with a slope angle of 30°... I do not think that "wall" is a proper word here.

Lines 162, 163, 173, 187. fracturing (see my first comment).

Line 271. based on my field observation I cannot say that rolling is a common process in rock avalanches, anlike fragmenting and sliding.

Citation: https://doi.org/10.5194/nhess-2021-127-RC1
- AC1: 'Reply on RC1', Qiwen Lin, 22 May 2021
  
  Thank you very much for your kindly comments and suggestions. We are glad that our work is read and discussed by any Anonymous experts. Based on your comments and suggestions, we've revised the manuscript.
  Line 65/Lines 162, 163, 173, 187. The usages of fracturing and fragmentation in manuscript are reconsidered and revised.
  Lines 86-89. It is unknow that is the main "after-fragmentation" effects. As shown by Lai et al. (2016), different fractal grain-size distribution may result in different runout of granular flow. However, the relationship between grain-size distribution and hypermobility of rock avalanches is still a very difficult question. Anyway, we've revised this sentence.
  Line 150. "wall" is replaced as "one".
  Line 271. We agree on that rolling is not a common process in rock avalanches. It is usually occurred at the surface of rock avalanching, but not the main body. Therefore, we added a explaination at this part.
  In case any comments and suggestions arise, please do not hesitate to contact us.
  
  Citation: https://doi.org/10.5194/nhess-2021-127-AC1
CC1:
'Comment on nhess-2021-127', chengsheng li, 22 Jun 2021

This paper attempted to study the fragmentation processes of rock block in rock avalanches via DEM simulations. Although the numerical model is extremely simplified, the research has produced some meaningful outcomes into the mechanisms of these processes. The quality of the work is generally good and logical reasonings are sound. Several comments and suggestions are presented hereafter:

Introduction: Haug et al. (2020) have some new comments on rock fragmentation in rock avalanche.

Haug Ø T, Rosenau M, Rudolf M, Leever K, and Oncken O. 2020. Short communication: Runout of rock avalanches limited by basal friction but controlled by fragmentation, Earth Surf. Dynam. Discuss. [preprint], https://doi.org/10.5194/esurf-2020-76.

Fig. 5 It would be unreliable to fit only three points to obtain the general relationship between velocity/energy increments & block strength.

Fig. 7 The symbols of the fragmentation stage should be revised.

Citation: https://doi.org/10.5194/nhess-2021-127-CC1
- AC2: 'Reply on CC1', Qiwen Lin, 22 Jun 2021
  
  Thank you for your insightful and helpful comments. All your comments and suggestions are considered.
  Haug et al. (2020) indicated that the runout of rock avalaches is dependence on fragmentation to be controlled by the competition between mobility enhancing spreading and energy consuming internal friction. His comments on rock fragmentation in rock avalanches were presented in the new version of manuscript.
  We agree with you on that the relationship between velocity/energy increments and block strength are unreliable with only three fit points. What we want to do is use a simple function to describe the increasing trend between those variables, but not trying to seek for the real correlation between variables. Thus, the incorrect expressions about trends and correlations are revised.
  Fig. 7 is revised now.
  Thank you very much.
  
  Citation: https://doi.org/10.5194/nhess-2021-127-AC2
RC2:
'Comment on nhess-2021-127', Anonymous Referee #2, 20 Oct 2021

The paper entitled “Multiscale effects caused by the fracturing and fragmentation of rock blocks in rock mass movement: Implications for rock avalanche propagation” reports a study on the relation between fracturing and fragmentation of sliding blocks and the propagation features of rock avalanches. The work is scientifically interesting; nevertheless, I have some criticism as commented in the following.

First of all, I suggest some corrections pertaining to the use of the English language.

I also suggest the authors to describe rock avalanches in a more “geomorphic” way in Ch. 1 - Introduction; in this regard I suggested some literature references.

Anyhow, the major issues concern the adopted methodology. In particular, I suggest to better explain some steps (e.g. line 152 – The gravitational acceleration (g’) is enhanced to 1962 m/s2 (200 g) to mimic the real stress field) based on literature data or other sources you considered. In this way, the comprehensibility of the whole work would surely be enhanced.

I also suggest to give a more detailed explanation concerning the relation between the number and spacing of fractures and the distance reached by blocks involved in the avalanche, since given explanation doesn’t sound accurate enough.

Finally, figures’ layout should be improved by applying a different colours palette and by indicating regressions equations and plots where available.

Please find suggested corrections and comments in the attached pdf file.

Based on these considerations, I do not suggest the publication of this paper before major revisions.

Regards

Citation: https://doi.org/10.5194/nhess-2021-127-RC2
- AC3: 'Reply on RC2', Qiwen Lin, 23 Nov 2021
  
  Thank you for the invaluable and insightful comments. We have read all your comments and suggestions. These comments and suggestions are important to improve our manuscript.
  
  (1) According to the references provided by the referee, the desciption of rock avalanches have been revised in a more "geomorphic" way in the Introduction section.
  
  (2) The methodology is not specific enough according to referee. So we presented more detailed information to better explain some steps. For example, the gravitational acceleration (g') is enhanced to 1962 m/s2, this choice is based on previous literature. We believe that the comprehensibility of our work will largely be enhanced with these revision.
  
  (3) The referee indicated that the given explanation of the relation between the number and spacing of fractures and the distance reached by blocks doesn't sound accurate enough. Actually, in that part of discussion, we attempted to discuss the relation between the strength of joint and the travel distance of fragments, which is still problematic. Thus, we detailed analyze the data, and trying to give a more robust explanation.
  
  (4) The figures are revised with different colours, and the fitting equations are presented at the plots.
  
  (5) The usage of fracture, fracturing, cracking, and fragmentation are reconsidered. After the revision, to further correct the English usage, grammar, and sentence structure, we will ask an English editing service to polish our revised manuscript.
  
  (6) All the corrections and comments in the attacched pdf file are concerned. A final revised manuscript and response letter will be presented latter.
  
  Thank you again!
  
  Citation: https://doi.org/10.5194/nhess-2021-127-AC3
- AC4: 'Reply on RC2', Qiwen Lin, 29 Nov 2021
  
  In order to further answer the referee's comments and suggestions, we upload a response letter to give more information. And the final response letter to two referees and revised manuscript will give in next step.
  
  Citation: https://doi.org/10.5194/nhess-2021-127-AC4

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Reconsider after major revisions (further review by editor and referees) (29 Nov 2021) by Mario Parise

AR by Qiwen Lin on behalf of the Authors (12 Jan 2022) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (15 Jan 2022) by Mario Parise

RR by Anonymous Referee #2 (18 Jan 2022)

RR by Anonymous Referee #1 (24 Jan 2022)

ED: Publish as is (25 Jan 2022) by Mario Parise

AR by Qiwen Lin on behalf of the Authors (27 Jan 2022) Author's response Manuscript

Short summary

Fracturing and fragmentation of rock blocks are important and universal phenomena during the movement of rock avalanches (large and long-run-out rockslide-debris avalanches). The movement of a fragmenting rock block is simulated by the discrete element method, aiming to quantify the fracturing and fragmentation effect of the block in propagation. The fracturing and fragmentation processes and their influences on energy transformation in the system are described in detail.