# Assessing the sensitivity of steep rock slope permafrost to water infiltration under various fracture geometries: a numerical approach

Josué Bock, Florence Magnin, Jean-Yves Josnin, Matan Ben-Asher

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Josué Bock, Florence Magnin, Jean-Yves Josnin, Matan Ben-Asher. Assessing the sensitivity of steep rock slope permafrost to water infiltration under various fracture geometries: a numerical approach. International Mountain Conference, Sep 2022, Innsbruck, Austria., 2021. [hal-04032881](https://hal.science/hal-04032881)

HAL Id: hal-04032881

https://hal.science/hal-04032881

Submitted on 30 Mar 2023

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# Assessing the sensitivity of steep rock slope permafrost to water infiltration under various fracture geometries: a numerical approach

Josué Bock¹, Florence Magnin¹, Jean-Yves Josnin¹, Matan Ben-Asher¹

¹Laboratoire EDYTEM, Université Savoie Mont-Blanc, CNRS, 73376 Chambéry, France

Water infiltration and circulation in frozen bedrock fractures may enhance heat transport from the surface to the permafrost body and play a role in rock slope failure. However, such processes occurring in steep rock slope permafrost are difficult to investigate because of their non-linearity and anisotropy.

<figure><img src="image_2.png" /><figcaption>Figure from Magnin and Josnin, JGR 2021</figcaption></figure>

Using a fully coupled hydrological and thermal model applied to rock wall permafrost, Magnin and Josnin shown that water flows have major effects on the aggradation and degradation of alpine rock wall permafrost, resulting in a deeper permafrost body than under heat conduction only.

in the frame of the WISPER project ("Water and Ice related thermo-mechanical processes in the fractures of Steep alpine bedrock Permafrost", funded by the French National Agency for Research), the sensitivity of steep rock slope permafrost is further investigated:

the FeFlow® (DHI-WASY, version 7.4) software is used to model and study the coupled heat and mass transfer in a simple alpine geometry that typically represents steep rock slope affected by permafrost and seasonal freeze and thaw cycles at c.a.3500 m a.s.l.

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Boundary condition:
Well (0,3 m³/d)
+ bounded head

Boundary conditions: synthetic annual cycles for N and S faces surface temperature:
- mean air temperature (-7 °C) consistent with elevation (3600 m a.s.l.)

- offset between air and rock surface temperature: +1 °C for N face, +6 °C for S face

Boundary condition:
Hydraulic head
+ max flow rate constrain

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Temperature divergence

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Boundary conditions which are
not honoured (deleted or
transformed)

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Numerical instability, fracture
emptied when the simulation
starts

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1 node select
44197 [d]

Perspective: limit the sensitivity study to a saturated case