STRESS INTERACTION BETWEEN MULTIPLE CREVASSES IN GLACIER ICE

The interaction between crevassing and far-field stresses at a glacier surface determines in part the distribution, orientation, surface den sity, and extent of propagation of crevasses. These properties charact erizing crevassing of a glacier surface are important parameters when modeling iceberg calving from glacier terminii, since they describe th e initial geometry of pre-existing cracks entering the calving front. Crack-by-crack modeling of fracture at a calving terminus is too compl ex a task to be modeled in full detail, however, and some means of sel ecting the crevasse features most significant in the stress field is d esired. We present a Boundary Element Analysis of the stress field sur rounding a group of cracks at the surface of a linear elastic half-spa ce and the part of the stress field arising from crack interactions al one. This stress field shows the extent to which individual crack stre ss fields interact, and gives a measure of the radius of interaction o f clacks. We find that typical crevasses in a glacier surface, formed in extension, cease to affect the stress field of neighboring crevasse s if the crevasses are separated by a distance greater than three to f our times the crevasse depth. This agrees well with limited observatio ns of crevasse depth and spacing, and with a separate theoretical anal ysis based on stress intensity factors, The calculation gives an expla nation of observed crevasse depth/spacing observations and provides a means for determining representative distributions of crevasse depths and spacings in a model based in part on calculations of far-field str esses.