Laboratory Compression Tests of Sea Ice at Slow Strain Rates From a Field Test Program

1988 ◽  
Vol 110 (2) ◽  
pp. 154-158 ◽  
Author(s):  
Y. S. Wang ◽  
J. P. Poplin
Keyword(s):  
Sea Ice ◽  
Strain Rate ◽  
Field Test ◽  
Ice Sheet ◽  
Field Tests ◽  
Crystallographic Structure ◽  
Strain Rates ◽  
Full Thickness ◽  
Test Program ◽  
Thin Sections

In the winter of 1979/80, five petroleum companies participated in a field test program conducted by Exxon Production Research Company in Prudhoe Bay, Alaska, to measure the unconfined compressive strength of the sea ice sheet in its full thickness at various strain rates between 10−7 and 8 × 10−5 s−1. As part of this program, ice sample blocks at four different levels in the ice sheet were collected from seven field test sites and shipped to Exxon’s Cold Laboratory in Houston. A total of 221 cylindrical ice samples were made from the ice blocks and tested for their compressive strengths on a closed loop test machine. The sample size was 2.725 in. (6.92 cm) in diameter and 5.75 in. (14.60 cm) long. The strain rate and temperature under which each sample was tested were selected to match actual field test conditions. In addition, 76 thin sections were prepared from tested samples and were studied for the crystallographic structure. Results indicate that local variations of the crystalline structure of the ice sheet could be significant and could cause large variations in the strength of individual samples. The results of the laboratory tests were used to estimate the strength of the full-thickness ice sheet by taking the average value of the through-thickness strength profile. Comparison with field tests shows that this procedure gives very accurate strength estimation for the strain rate range used in the field tests.

scholarly journals Strain-Rate and Grain‒Size Effects in Ice

1987 ◽  
Vol 33 (115) ◽  
pp. 274-280 ◽  
Author(s):  
David M. Cole
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Transition Point ◽  
Boundary Migration ◽  
Peak Stress ◽  
Strain Rates ◽  
Thin Sections ◽  
Fine Grained ◽  
Lower Strain ◽  
Polycrystalline Ice

AbstractThis paper presents and discusses the results of constant deformation-rate tests on laboratory-prepared polycrystalline ice. Strain-rates ranged from 10−7to 10−1s−1, grain–size ranged from 1.5 to 5.8 mm, and the test temperature was −5°C.At strain-rates between 10−7and 10−3s−1, the stress-strain-rate relationship followed a power law with an exponent ofn= 4.3 calculated without regard to grain-size. However, a reversal in the grain-size effect was observed: below a transition point near 4 × 10−6s−1the peak stress increased with increasing grain-size, while above the transition point the peak stress decreased with increasing grain-size. This latter trend persisted to the highest strain-rates observed. At strain-rates above 10−3s−1the peak stress became independent of strain-rate.The unusual trends exhibited at the lower strain-rates are attributed to the influence of the grain-size on the balance of the operative deformation mechanisms. Dynamic recrystallization appears to intervene in the case of the finer-grained material and serves to lower the peak stress. At comparable strain-rates, however, the large-grained material still experiences internal micro-fracturing, and thin sections reveal extensive deformation in the grain-boundary regions that is quite unlike the appearance of the strain-induced boundary migration characteristic of the fine-grained material.

scholarly journals Mechanical behaviour and structure of snow under uniaxial tensile stress

1980 ◽  
Vol 26 (94) ◽  
pp. 275-282 ◽  
Author(s):  
Hidek Narita
Keyword(s):  
Tensile Stress ◽  
Strain Rate ◽  
Mechanical Behaviour ◽  
Maximum Strength ◽  
Ductile Deformation ◽  
Uniaxial Tensile ◽  
Strain Rates ◽  
Thin Sections ◽  
Uniaxial Tensile Stress ◽  
Small Cracks

AbstractThe mechanical behaviour of snow was studied at — 10°C under uniaxial tensile stress in a range of cross-head speed 6.8 × 10–8to 3.1 × 10–4ms–1and snow density 240-470 kg m–3.It was found from the resisting force-deformation curves that the snow was deformed in two different ways: namely, brittle and ductile deformation at high and low strain-rates, respectively. The critical strain-rate dividing the two deformation modes was found to depend on the density of snow. In ductile deformation, many small cracks appeared throughout the entire specimen. Their features were observed by making thin sections and they were compared with small cracks formed in natural snow on a mountain slope.The maximum strength of snow was found to depend on strain-rate: at strain-rates above about 10–5s–1, the maximum strength increased with decreasing strain-rate but below 10–5s–1it decreased with decreasing strain-rate.

scholarly journals Mechanical behaviour and structure of snow under uniaxial tensile stress

1980 ◽  
Vol 26 (94) ◽  
pp. 275-282 ◽  
Author(s):  
Hidek Narita
Keyword(s):  
Tensile Stress ◽  
Strain Rate ◽  
Mechanical Behaviour ◽  
Maximum Strength ◽  
Ductile Deformation ◽  
Uniaxial Tensile ◽  
Strain Rates ◽  
Thin Sections ◽  
Uniaxial Tensile Stress ◽  
Small Cracks

AbstractThe mechanical behaviour of snow was studied at — 10°C under uniaxial tensile stress in a range of cross-head speed 6.8 × 10–8 to 3.1 × 10–4 ms–1 and snow density 240-470 kg m–3.It was found from the resisting force-deformation curves that the snow was deformed in two different ways: namely, brittle and ductile deformation at high and low strain-rates, respectively. The critical strain-rate dividing the two deformation modes was found to depend on the density of snow. In ductile deformation, many small cracks appeared throughout the entire specimen. Their features were observed by making thin sections and they were compared with small cracks formed in natural snow on a mountain slope.The maximum strength of snow was found to depend on strain-rate: at strain-rates above about 10–5 s –1, the maximum strength increased with decreasing strain-rate but below 10–5 s–1 it decreased with decreasing strain-rate.

scholarly journals Strain-Rate and Grain‒Size Effects in Ice

1987 ◽  
Vol 33 (115) ◽  
pp. 274-280 ◽  
Author(s):  
David M. Cole
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Transition Point ◽  
Boundary Migration ◽  
Peak Stress ◽  
Strain Rates ◽  
Thin Sections ◽  
Fine Grained ◽  
Lower Strain ◽  
Polycrystalline Ice

AbstractThis paper presents and discusses the results of constant deformation-rate tests on laboratory-prepared polycrystalline ice. Strain-rates ranged from 10−7 to 10−1s−1, grain–size ranged from 1.5 to 5.8 mm, and the test temperature was −5°C.At strain-rates between 10−7 and 10−3 s−1, the stress-strain-rate relationship followed a power law with an exponent of n = 4.3 calculated without regard to grain-size. However, a reversal in the grain-size effect was observed: below a transition point near 4 × 10−6 s−1 the peak stress increased with increasing grain-size, while above the transition point the peak stress decreased with increasing grain-size. This latter trend persisted to the highest strain-rates observed. At strain-rates above 10−3 s−1 the peak stress became independent of strain-rate.The unusual trends exhibited at the lower strain-rates are attributed to the influence of the grain-size on the balance of the operative deformation mechanisms. Dynamic recrystallization appears to intervene in the case of the finer-grained material and serves to lower the peak stress. At comparable strain-rates, however, the large-grained material still experiences internal micro-fracturing, and thin sections reveal extensive deformation in the grain-boundary regions that is quite unlike the appearance of the strain-induced boundary migration characteristic of the fine-grained material.

Compressive strength of iceberg ice

2003 ◽  
Vol 81 (1-2) ◽  
pp. 191-200 ◽  
Author(s):  
S J Jones ◽  
R E Gagnon ◽  
A Derradji ◽  
A Bugden
Keyword(s):  
Grain Size ◽  
Compressive Strength ◽  
Strain Rate ◽  
Strain Rate Range ◽  
Air Bubbles ◽  
Strain Rates ◽  
Thin Sections ◽  
Rate Range ◽  
A Value ◽  
Wide Range

The uniaxial compressive strength of iceberg ice was determined over a wide range of strain rates from 10–8 to 10+1 s–1 at –10°C. It was found that for strain rates less than 10–4 s–1, strength increased in a power-law manner with strain rate. Above 10–4 s–1, the strength was essentially constant at 4 MPa, dropping slightly between 10–3 and 10–1 s–1, before rising again to a value of about 10 MPa at 10+1 s–1. Thin sections of the ice revealed a small grain size of about 3.5 mm and elongated air bubbles with a ratio of length to width of about 10. In the practical strain-rate range of interest, the maximum failure stress observed was 4.8 MPa. PACS No.: 62.20

Ice Pressure Sensor Inclusion Factors

1981 ◽  
Vol 103 (1) ◽  
pp. 82-86 ◽  
Author(s):  
A. C. T. Chen
Keyword(s):  
Sea Ice ◽  
Pressure Distribution ◽  
Pressure Sensor ◽  
Pressure Measurement ◽  
Measurement Data ◽  
Ice Sheet ◽  
Field Tests ◽  
Approximate Equation ◽  
Analytical Work ◽  
Ice Pressure

The inclusion of a pressure sensor in an ice sheet will disturb the pressure distribution in the ice sheet. The ratio of undisturbed ice pressure to the pressure felt by the sensor, defined herein as the inclusion factor, is required in interpreting the ice pressure measurement data. An approximate equation which expresses the inclusion factor in terms of the geometry of sensor and the sea ice/pressure sensor stiffnesses ratio is proposed in this study. Some results of analytical work and field tests which were performed to evaluate the accuracy of this expression are also presented. These results demonstrate the validity of the proposed inclusion equation.

The Distribution of Ice Pressure Acting on Offshore Pile Structure and the Failure Mechanics of Ice Sheet

1987 ◽  
Vol 109 (1) ◽  
pp. 85-92 ◽  
Author(s):  
S. Tanaka ◽  
H. Saeki ◽  
T. Ono
Keyword(s):  
Aspect Ratio ◽  
Strain Rate ◽  
Local Buckling ◽  
Ice Sheet ◽  
Field Tests ◽  
Ice Thickness ◽  
Economic Factors ◽  
Failure Mechanics ◽  
Ice Pressure ◽  
Ice Force

The total ice force acting on offshore pile structures, located in cold regions, has already been investigated by many researchers. Few papers, however, have described the distribution of ice pressure on the structures and the failure mechanics of ice sheet. It is necessary to study them in order to design the pile structures, keeping in mind safety and economic factors. The results of our experiments on failure mechanics of an ice sheet are useful for dynamic analysis. For analysis of stress and, especially, local buckling of structures, it is essential to examine the distribution of ice pressure acting on the structures. This paper describes a systematic study of these aspects through field tests with three rectangular piles (20, 40, 60 cm in width) in Saroma Lagoon in Hokkaido, Japan’s northernmost island, to clarify the effect of aspect ratio. It is clear from our experiments on ice pressure that the distribution of ice pressure can be classified into two types according to the strain rate ε˙ (= V/4B, V: penetration velocity of piles, B: pile width) defined by Michel and Toussaint [1] in each aspect ratio, B/h (h: ice thickness). It is our hypothesis that the failure periods of ice sheet are determined by the aforementioned strain rate and the aspect ratio.

A Flow-line Model for Calculating the Surface Profile and the Velocity, Strain-rate, and Stress Fields in an Ice Sheet

1988 ◽  
Vol 34 (116) ◽  
pp. 46-55 ◽  
Author(s):  
Niels Reeh
Keyword(s):  
Strain Rate ◽  
Vertical Velocity ◽  
Flow Line ◽  
Ice Sheet ◽  
Surface Profile ◽  
Surface Elevation ◽  
Stress Fields ◽  
Strain Rates ◽  
Line Model ◽  
Depth Distributions

AbstractA flow-line model is presented for calculating the surface profile and the velocity, strain-rate, and stress fields in an ice sheet with given base-elevation profile, ice thickness at the dome (divide), flow-law parameters, mass-balance distribution, and convergence/divergence conditions along the flow line. The model, which is based on a “quasi-similarity” hypothesis as regards the horizontal velocity-depth profiles, accounts for changes along the flow line in the depth distributions of temperature, normal stress deviators, and possible enhanced flow of deep ice of Wisconsin origin. A curvilinear coordinate system is applied with horizontal axes along flow lines and surface-elevation contours, respectively. The flow equations are reduced to two differential equations, one for the surface-elevation profile, and the other for a profile function that determines the depth distributions of velocities and strain-rates. The two equations are coupled through a profile parameter that communicates the influence of velocity-profile changes to the surface-profile equation. It is shown that the variation along the flow line of this parameter should also be considered when deriving flow-law parameters from ice-sheet flow-line data. For a symmetric dome, explicit expressions are derived for the depth distributions of the vertical velocity, strain-rates, and stresses. The strain-rate profiles display an inflection about half-way down the ice sheet, and, in the case of isothermal ice, have surface values 2.2 times their depth-averaged values. The depth distribution of the vertical velocity indicates that a relatively thick layer of almost stagnant ice is present at the ice-sheet base below a dome.

scholarly journals The tensile strength of first-year sea ice

1993 ◽  
Vol 39 (133) ◽  
pp. 609-618 ◽  
Author(s):  
J. A. Richter Menge ◽  
K. F. Jones
Keyword(s):  
Tensile Strength ◽  
Sea Ice ◽  
Maximum Stress ◽  
Ice Sheet ◽  
Tensile Load ◽  
Growth Direction ◽  
First Year ◽  
Strain Rates ◽  
Temperature Dependent

AbstractWe present the results of tests done to determine the tensile behavior of first-year columnar sea ice over a range of temperatures from −20° to −3°C and strain rates of 10−5and 10−3s−1. The temperature of a test specimen was dictated by its in-situ location within the sea-ice sheet; samples located near the top of the sea-ice sheet were tested at the lower temperatures. A tensile load was applied along the cylindrical axes of the test specimens, which were perpendicular to the growth direction of the ice. Results showed that the maximum stress reached during a test was most strongly influenced by temperature, while the failure strain and the modulus were principally affected by the loading rate. A model relating the tensile strength of the ice to its porosity based on temperature-dependent variations in the brine-pocket geometry is evaluated.

Full-Scale In-Situ Four-Point Beam Bending Field Tests on Sea Ice

2021 ◽  
Author(s):  
Rocky Taylor ◽  
Ian Turnbull ◽  
Eleanor Bailey-Dudley ◽  
Rob Pritchett
Keyword(s):  
Flexural Strength ◽  
Sea Ice ◽  
Scale Effects ◽  
Field Tests ◽  
Basic Material ◽  
Measured Temperature ◽  
Full Thickness ◽  
Loading System ◽  
Beam Bending

Abstract The flexural strength of ice is not a basic material property, but rather is an estimate of the maximum stress in the outermost fiber of an ice specimen when it fails in bending. Such conditions correspond to a number of important engineering applications, such as interactions between ice and a sloping structure or between ice and ships. Ice flexural strength is therefore highly important for calculating ice pressures and forces of interest for engineering design. While there has been considerable discussion in the literature regarding scale effects related to ice crushing against a vertical structure, scale effects in relation to bending failure have received much less attention. To this end, more flexural strength data for large, full-thickness sea ice beams are needed. To address these data gaps, a field data collection program was carried out in Pistolet Bay, Newfoundland over two field seasons (2017–2018). During this program, large sea ice beams were tested in-situ using a custom four-point bending apparatus, which was comprised of several main subsystems (e.g., the ram loading system, the platen, the ubrackets, and the hydraulic system). The sea ice beams were completely cut free from the ice cover and loaded at four points, such that the center load is parallel, but opposed to, the loads at the ends of the beam. All tests were done in-situ so that no brine drainage took place and the temperature gradient remained consistent. Tests were carried out for several combinations of beam geometry, which were scaled relative to the ice thickness. In addition to flexural strength, during the Pistolet Bay field program, the physical properties of the ice were measured (temperature, salinity, density). In this paper, a description of the field apparatus, test program and results from the full-thickness in-situ four-point beam bending tests are presented, along with a discussion of practical implications and future work.

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