MECHANISM OF BEDROCK FROST HEAVE IN PERMAFROST REGIONS

• Main Authors: Yves Michaud, Larry D. Dyke
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Ice; permafrost
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.568.8671; http://pubs.aina.ucalgary.ca/cpc/CPC5-125.pdf

Frost heaving of bedrock is a widespread process in permafrost regions which may generate forces and movements that detract from the otherwise sound foundation performance usually associated with bedrock. Depending on pre-existing fracture fabric, bedrock heave features may take the form of single ejected blocks or dome-shaped accumulations of up to several meters in diameter. The development of excess pressure by water trapped between the permafrost table and downward freezing has been identified as an origin for the forces producing these types of features. Enclosed in the active layer, the water occupying fracture apertures and spaces vacated by heaved rock gives rise to a: pulsating movement The saturated volume determines the amount of heave possible under freeze back. Heave occurs when the sirength contributed by ice-filled fractures is exceeded by excess water pressure; high water pressure being obtained by an increase in the rate of freezing. Knowing that the main resistance to heave is offered by the weight and the shear resistance of the overlying ice-bonded rock mass, the behaviour of frost-heaved bedrock blocks is determined by the mechanical properties of the ice-filling material. Laboratory experiments indicate that even with a freezing rate 60 times faster than in the field situation, the ice-filling still deforms plastically. The vertical displacement of bedrock blocks is then characterized by a