Triaxial experiments on iceberg and glacier ice

Abstract

Triaxial experiments, at confining pressures in the range 0–13.79 MPa, have been performed on glacial ice collected from four icebergs and one glacier. Tests were conducted at strain rates in the range of 5 × 10−5 to 5 × 10−5s−1 and at four temperatures in the range of −1° to −16°C. Depending on test conditions, the ice failed by one of four possible modes ductile deformation, due to extensive non-interacting microcracks; fracture along a shear plane followed by continuous or stick-slip sliding; large-scale brittle fracture; and combined ductile and shear-plane fracture and slip The strength Increased with decreasing temperature, increasing strain rate up to 5 × 10−3s−1 and increasing confining pressure at the lower temperatures. The strength at 5 × 10−2s−1 was lower than at 5 × 10−3s−1 probably because extension and interaction of microcracks is enhanced at the higher rate. For higher confining pressures at −1°C, the strength decreased due to freezing-point depression. The ice from the different sources exhibited different mean uniaxial compressive strengths. The mean number of air bubbles per unit volume correlated with the mean uniaxial compressive strengths and this may be the dominant factor distinguishing the strengths of the various ice types.

Ice shedding from overhead electrical lines by mechanical breaking :

“…Typical temperature dependence of ice cohesion for granular (left) and columnar S2 (right) ice types, curves are fitted to the data of Refs. [21], [25], and [50] 97 (left) and columnar S2 (right) ice types, curves are fitted to the data of Refs. [21], [25], and [50] 99 Typical temperature dependence of the pressure at maximum shear strength p^fCI) for bubble-free granular (left) and columnar S2 (right) ice types, curves are fitted to the data of Refs.…”

“…[21], [25], and [50] 97 (left) and columnar S2 (right) ice types, curves are fitted to the data of Refs. [21], [25], and [50] 99 Typical temperature dependence of the pressure at maximum shear strength p^fCI) for bubble-free granular (left) and columnar S2 (right) ice types, curves are fitted to the data of Refs. [21], [25], and [50] Temperature dependency of columnar S2 ice yield envelope, the tests data are adopted from Jones (1982) at -11.8°C for strain rate 4.7xlO" 3 s" 1 , and Gagnon and Gammon (1995) (2000) for freshwater granular ice, the tests data are adopted from Rist and Murrell (1994)at-40°C 167…”

“…A comparison between the yield (failure) envelopes of this model and Fish et al (1997) for columnar S2 ice, the tests data are adopted from Gagnon and Gammon (1995)at - The comparison of the contours of displacement (in meter) in xl-direction (Ul) and the corresponding legends for the ice structures of the cases GS1 and GS3-0-10 at confining pressure of 0.5xl0 6 Pa 184 Table 2.1: Adiabatic measurements of ice monocrystal elastic constants at -16°C, Gammon et al (1983) 32 Table 2.2: Material parameters in viscoelastic formulation of freshwater ice at -10°C, Ref. [14] and [58] 35 Table 5.1: Material constants involved in the formulation of ice cohesion for granular and columnar S2 ice types 97 Table 5.2: Material constants involved in the formulation of ice friction parameter for granular and columnar S2 ice types 99 Table 5.3: Variation of ice friction parameter b versus strain rate for granular and columnar ice types at-11.8°C calculated from the data of Jones (1982) 101 Table 5.4: Material constants involved in the formulation of ice pressure at maximum shear strength for granular and columnar ice types 103 Table 5.5: Variation of ice pressure at maximum shear strength versus strain rate for granular and columnar ice types at -11.8°C calculated from the data of Jones (1982) 103 Table 7.1: Material constants (PROPS) defined in UMAT subroutine 160 …”

“…Hausler (1983), Nadreau and Michel (1986), Richter-Menge et al (1986), Timco and Frederking (1984), Sinha (1985, Nadreau et al (1991), Rist and Murrell (1994), Gagnon and Gammon (1995), Weiss and Schulson (1995), Fish et al (1997) and others reported the results of a series of confined multiaxial compression tests with various ice types and over a range of loading rates, confinements, and temperatures. They deduced that the confined ice strength could be ten times greater than the uniaxial case.…”

“…The temperature dependence of failure envelopes are shown in Fig. 2.6a by Fish et al (1997) on the basis of the test data of Rist and Murrell (1994), Jones (1982), and Gagnon and Gammon (1995). The variations of failure envelopes by strain rate were presented by Jones (1982) in Fig.…”