TRIAXIAL EXPERIMENTS ON ICEBERG AND GLACIER ICE

Triaxial experiments, at confining pressures in the range 0-13.79 MPa, ha re been performed on glacial ice collected from four icebergs and one glacier. Tests were conducted at strain rates in the range of 5 x 10(-5) to 5 x 10(-2) s(-1) and at four temperatures in the range of -1 degrees to -16 degrees C. Depending on test conditions, the ice faile d by one of four possible modes: ductile deformation, due to extensive noninteracting microcracks; fracture along a shear plane followed by continuous or stick-slip sliding; large-scale brittle fracture: and co mbined ductile and shear-plane fracture and slip. The strength increas ed with decreasing temperature, increasing strain rate up 5 x 10(-3) s (-1) and increasing confining pressure at the lower temperatures. The strength at 5 x 10(-2) s(-1) was lower than at 5 x 10(-3) s(-1) probab ly because extension and interaction of microcracks is enhanced at the higher rate. For higher confining pressures at -1 degrees C, the stre ngth decreased due to Freezing-point depression. The ice from the diff erent sources exhibited different mean uniaxial compressive strengths. The mean number of air bubbles per unit volume correlated with the me an uniaxial compressive strengths and this may be the dominant factor distinguishing the strengths of the various ice types.