A permafrost test on intact gneiss rock. (July 2015)

• Record Type: Journal Article
• Authors: Duca, S.; Alonso, E.E.; Scavia, C.
• Is Part Of: International journal of rock mechanics and mining sciences. Volume 77(2015:Jul.)
• Page Start: 142
• Page End: 151
• Publication Date: 2015-07
• Subjects: Ice segregation -- Gneiss -- Laboratory test -- THM modeling -- Fracturing -- Wave propagation; Rock mechanics -- Periodicals; Soil mechanics -- Periodicals; Mining engineering -- Periodicals; Roches, Mécanique des -- Périodiques; Sols, Mécanique des -- Périodiques; Technique minière -- Périodiques; 624.151305
• DOI: 10.1016/j.ijrmms.2015.02.003
• Languages: English
• ISSNs: 1365-1609

Abstract

Abstract: Changes in permafrost conditions in high mountain rocks have increased the risk of dangerous instabilities. Ice segregation within the rock mass has been interpreted as one of the mechanisms involved in high mountain bedrock degradation. A long term laboratory test on a cube of intact gneiss has been designed to reproduce field temperature gradients and water supply conditions. Test results demonstrate that ice crystallization in a permafrost fringe ( T =0 °C to −3 °C) leads to the formation of continuous ice-filled cracks which explain the loss of rock continuity and the observed rock failures. A coupled thermo-hydro-mechanical model which incorporates the thermodynamics of ice-water mixtures has been used to reproduce test results. The model, which follows existing formulations for unsaturated porous media, was capable of capturing the main observations derived from the experiment. Calculated tensile stresses are close to the gneiss tensile strength. The analysis performed is a step forward in understanding field observations and in the application of computational tools to real cases. Highlights: A laboratory test on intact hard rock, which shows that ice may segregate at a well defined position creating a discontinuity in the rock matrix. The implication is that permafrost driven rockfalls do not require the presence of previously existing rock discontinuities to become active. A model capable of predicting the generation of the ice segregation front with good accuracy. The model uses principles that have previously been shown to be accurate and thermodynamically sound when analyzing ice-induced heave in soils.