Creep of polar firn

It is the aim of the paper presented here to describe the creep behaviour o f polar firn. To do so, creep tests under tension, compression and combined torsion-compression load were performed. The samples tested were examined to testify their structural properties and were classified to ensure compar ability. The results of the structural investigation and of the creep tests are used to describe the creep behaviour of polar firn with von Mises pote ntials. The material properties are then derived from numerical analysis of the creep curves. The authors found two constitutive features of the mater ial properties. The first is the volume viscous behaviour of the firn. The dependency of the material properties on the density is tremendous. The sec ond feature arises from the granular structure of the firn. It gives rise t o volume increase under shear loading (dilatation). The findings are used t o derive a Finite Element Model for firn. (C) 1999 Elsevier Science B.V. Al l rights reserved.