the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 18 Sep 2024
Brief Communication: Mimicking periglacial landforms and processes in an ice-rich layered permafrost system with polydispersed melamine materials: a new concept
Abstract. This paper presents results on testing polydisperse melamine material versus sand for laboratory ice-rich layered soil system under thawing conditions. We demonstrate the potential of using polydisperse melamine particles in the aim of mimicking the permafrost geomorphological degradations and landslide found in periglacial field environments. We stress that this type of particles, designed for flow and sedimentary processes in river due to their light particle density and the granulometric size they span, are as well adequate for modeling more realistic geomorphological thawing features observed in cryosphere environments such as slump blocks.
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Status: final response (author comments only)
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RC1: 'Comment on egusphere-2024-2690', Anonymous Referee #1, 05 Nov 2024
This is interesting and timely work. Some comments:
1. The abstract is easy to follow overall. What does ‘mimicking’ mean, experimental evaluation or numerical simulation?
2. The limitations of laboratory experiments are not well described. Therefore, the motivation for using PPP is not clear; please revise it.
3. What are the benefits of using PPP compared to conventional sand/soil materials?
4. Figure 1 is excellent.
5. The size distribution of PPP will significantly influence the flow and sedimentary behaviour. Please explain the specific particle size selection criteria.
6. The authors mentioned potential future perspectives, such as exploring scaling relations and 3D numerical modelling. Please be more specific.Citation: https://doi.org/10.5194/egusphere-2024-2690-RC1 -
AC1: 'Reply on RC1', Emmanuel Léger, 10 Nov 2024
Dear RC1 Thank you for your very constructive comments,
Please find our answer in the enclosed file.
Best
Emmanuel Léger
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RC3: 'Reply on AC1', Anonymous Referee #1, 11 Nov 2024
Thanks to the authors' hard work, almost all my comments were revised. No further review process is needed.
Citation: https://doi.org/10.5194/egusphere-2024-2690-RC3
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RC3: 'Reply on AC1', Anonymous Referee #1, 11 Nov 2024
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AC1: 'Reply on RC1', Emmanuel Léger, 10 Nov 2024
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RC2: 'Comment on egusphere-2024-2690', Anonymous Referee #1, 11 Nov 2024
Thanks to the authors' hard work, almost all my comments were revised. No further review process is needed.
Citation: https://doi.org/10.5194/egusphere-2024-2690-RC2 -
AC2: 'Reply on RC2', Emmanuel Léger, 03 Dec 2024
Dear reviewer,
Thank you for your very constructive and high scientific level comment you wrote.
The paper was thought of as a preliminary approach on using PPP to mimic some typical periglacial morphologies observed in arctic regions. We wanted to use the peculiar PPP hydrodynamical properties, and their light weight to trigger geomorphological features we were not able to observe with sand. This is why we aimed for a brief communication issue as a first study. We are aware that the size is not the main factor affecting the analog of the RTS at lab scale, and this is why we concluded the paper with the following sentence (Following R1 remarks):
“Further investigations are needed to determine the scaling relations between parameters, which allow the transpose of similarity between model and prototype. This implies the use of dimensionless parameters, such as the densimetric Froude number, the grain size Reynolds number and the Engelund–Hansen formula, similar between the analog and the field model. We plan as well to complement the surface change with time-lapse 3D reconstruction, using photogrammetry or laser scanning.”- "Such differences are not simply size, but may change the relevant phenomena that control RTS. Quite old research (Lewkowitz) suggests that positive pore-pressures developed during thaw play a strong role in the progression of RTs, for example. Therefore, the weight of the soil at depth is important. Relevant dynamics of thaw vs flow and their differences across scale should also be considered". As you mentioned, the scale of the landslide increased as the depth was increasing in the laboratory simulation, but some other parameters could be important such as the depth of the active layer, the ice content. We did not measure the pore pressure for these experiments as we were doing very preliminary research. This will be the object of future studies.
- "The authors comment on the differences in hydraulic properties and seem to imply these are dominant. My first reaction upon reading the document is that the mechanical property difference needs to quantified, as strength loss / volume change in in the much looser PPP samples would be much greater than for the sand. As someone who would like to try simulation this kind of test, that information would be required" Concerning the hydraulic properties, these were the easiest to measure for both types of material and were an indication of the hydrodynamical contrast between these two materials. The mechanical properties necessitate more time, as well as any rheological analysis.
Such a topic needs further developments in our laboratory and much more experiments are necessary in the near future. - "The authors comment on the likely mobility of the PPP material. I presume they mean the rheology, which is important as a risk posed by RTS is the run-out, sometimes to considerable distances, of the thawed soil. More information on the rheological properties of the thawed sand and PPP, and how these compare with rheology inferred from field observations, would be of interest". We meant the mobility of the particles, because we were able to track them in the images. This is, in a way, a consequence of rheology. Once again, the purpose of this brief communication was to visually observe peculiar geomorphological phenomena that are not classically observed in sand experiments
Based on your comments, we have added the following sentence to the conclusion
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We are aware that the role of positive pore pressure is crucial for the development of RTS and that the rheological properties of sand vs. PPP are needed to fully quantify the dynamics of thaw vs. flow. This will be the subject of further studies.”Best regards
Emmanuel
Citation: https://doi.org/10.5194/egusphere-2024-2690-AC2
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AC2: 'Reply on RC2', Emmanuel Léger, 03 Dec 2024
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RC4: 'Comment on egusphere-2024-2690', Anonymous Referee #2, 30 Nov 2024
This is an interesting study and the potential application of the novel material for use in physical simulations of RTS should be explored further. Some comments:
i) the authors should be mindful of the differences in scale between such small tests and the real behaviour in the field. Such differences are not simply size, but may change the relevant phenomena that control RTS. Quite old research (Lewkowitz) suggests that positive pore-pressures developed during thaw play a strong role in the progression of RTs, for example. Therefore, the weight of the soil at depth is important. Relevant dynamics of thaw vs flow and their differences across scale should also be considered. While the type of study reported by the authors if of interest from a numerical modelling perspective (to test models under a controlled environment), the authors should discuss problems of scaling in the present document, and consider if the match in the morphology of retrogression is controlled by different factors in the field than might be at the bench scale.
The authors comment on the differences in hydraulic properties and seem to imply these are dominant. My first reaction upon reading the document is that the mechanical property difference needs to quantified, as strength loss / volume change in in the much looser PPP samples would be much greater than for the sand. As someone who would like to try simulation this kind of test, that information would be required.
The authors comment on the likely mobility of the PPP material. I presume they mean the rheology, which is important as a risk posed by RTS is the run-out, sometimes to considerable distances, of the thawed soil. More information on the rheological properties of the thawed sand and PPP, and how these compare with rheology inferred from field observations, would be of interest.
Citation: https://doi.org/10.5194/egusphere-2024-2690-RC4
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