Monitoring of thermal contraction cracking at an ice wedge site, central Spitsbergen

• Main Author: Norikazu Matsuoka
• Format: Report
• Language: English
• Published: Institute of Geoscience, University of Tsukuba 1999
• Subjects: ice wedge; thermal constraction crack; permafrost; field measurement; Svalbard; Ice; Polar geoscience; wedge*; Spitsbergen
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=3057; http://id.nii.ac.jp/1291/00003057/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=3057&item_no=1&attribute_id=18&file_no=1

Thermal contraction cracking was monitored for two years in a continuous permafrost region. A dilatometer read the separation of a pair of benchmarks installed at both sides of an ice-wedge trough. The outputs were recorded in a data logger together with ground temperatures at various depths. Widening of the trough was insignificant during the warmer first winter, while several significant events occurred during the colder second winter. The amount of widening reflected the magnitude of cooling. The maximum widening in the second winter corresponded to the most severe cooling in early February, during which the frozen active layer experienced significant creep, possibly accompanied by cracking. The ground temperature data were analyzed on the basis of a viscoelastic model, which shows that horizontal tensile stress is favored by higher cooling rates and colder ground. The predicted maximum stress at the ground surface and at the permafrost table, which was reached during the maximum widening event, is of the same order of magnitude as the tensile strengths of typical frozen soils and polycrystalline ice, respectively. Consequently, the ground thermal regime during this event was capable of cracking both the frozen active layer and the ice wedge.