Unstable Alpine Permafrost: A Potentially Important Natural Hazard Variations of Geotechnical Behavior with Time and Temperature
A Potentially Important Natural Hazard - Variations of Geotechnical Behaviour with Time and Temperature
1st Edition
Published on 22. May 2003
Book
Paperback/Softback
308 pages
978-3-7281-2883-6 (ISBN)
Description
One of the key conclusions arising from the National Research Project No. 31 on Natural Hazards was that melting mountain permafrost would cause one of the most important natural hazards in Switzerland. Mountain permafrost, in the form of alpine rock glaciers, covers about 5% of the area of Switzerland and is to be found mainly above 2500 m above sea level.
Previous research has focused on the geomorphological, geological and glaciological aspects of these phenomena with extensive field campaigns to measure deformations and temperatures within the permafrost body. However, the threat of climate warming will lead to clear consequences for existing permafrost, in that the ice will warm and eventually melt, creating either high pore pressures or releasing water into the rock glacier matrix. This is associated with potential for sliding of the increasingly deeper active layer, or indeed a failure through the rock glacier itself, with dire consequences for those living in the valleys below.
In judging whether a rock glacier is on the verge of failure, it is extremely important to be able to understand the thermo-hydro-mechanical response of the rock glacier to the environmental conditions, so that predictions could be made of the potential hazard. The author undertook two field campaigns in the Engadin to drill into the permafrost to obtain undisturbed samples. In comparing the potential hazards from both rock glaciers, he analysed the deformation profiles, predicted future behaviour and discussed a range of possible failure mechanisms. He concluded that the steeper and faster moving Muragl rock glacier was probably not at risk of failure due to the coarse, free draining nature of the material, whereas Murtèl-Corvatsch has more potential for porewater pressure build up within the rock glacier mass due to the hydrological regime. However, further research is necessary for modelling the effect of future temperature variations, especially where this includes a change of state of the ice into water.
Previous research has focused on the geomorphological, geological and glaciological aspects of these phenomena with extensive field campaigns to measure deformations and temperatures within the permafrost body. However, the threat of climate warming will lead to clear consequences for existing permafrost, in that the ice will warm and eventually melt, creating either high pore pressures or releasing water into the rock glacier matrix. This is associated with potential for sliding of the increasingly deeper active layer, or indeed a failure through the rock glacier itself, with dire consequences for those living in the valleys below.
In judging whether a rock glacier is on the verge of failure, it is extremely important to be able to understand the thermo-hydro-mechanical response of the rock glacier to the environmental conditions, so that predictions could be made of the potential hazard. The author undertook two field campaigns in the Engadin to drill into the permafrost to obtain undisturbed samples. In comparing the potential hazards from both rock glaciers, he analysed the deformation profiles, predicted future behaviour and discussed a range of possible failure mechanisms. He concluded that the steeper and faster moving Muragl rock glacier was probably not at risk of failure due to the coarse, free draining nature of the material, whereas Murtèl-Corvatsch has more potential for porewater pressure build up within the rock glacier mass due to the hydrological regime. However, further research is necessary for modelling the effect of future temperature variations, especially where this includes a change of state of the ice into water.