Materialparameter zur Beschreibung des zeitabhängigen nichtlinearen Spannungsverformungsverhaltens von Firn in Abhängigkeit von seiner Dichte

The aim of this work is the derivation of material parameters of polar firn as a function of its density to describe the time-dependent deformation behaviour under compressive stress. The total pressure corresponding to the in situ depths of the firn layer is taken into account. The linear and the nonlinear stress-strain relation will be investigated. The use of simple constitutive equitation to describe settlement measurements in boreholes near the Georg von Neumayer Station in Antarctica yields material parameters to describe the time-independent linear deformation behaviour. Results of uniaxial and triaxial compression and creep tests on "in-situ ice cores" under high pressure are first described by a nonlinear constitutive equitation which yields the material parameters without consideration of the time dependency. A further consideration with the same nonlinear constitutive equitation will take into account the time dependency, and the resulting density-dependent material parameters will be identified. After conversion of the constitutive equitation to calculate the stress and in consideration of the strain at failure compressive strength are calculated. The indirect theoretically determined compressive strength (follows the above mentioned procedure) correspond well with those identified in laboratory tests.