Tests have been conducted on freshwater columnar ice samples to determine the uniaxial and triaxial compressive strength of the ice. Four parameters were varied. The confining pressure was increased up to 2.85 MPa (400 psi) in steps of 0.7 MPa (100 psi). The strain rate was varied in order to obtain the ductile to brittle transition peak. Temperature was kept mainly at −2°, with two series at −10°C and −20°C, and samples were machined with axes parallel, perpendicular or at a 45-deg angle to the direction of ice growth. The results are presented within their original context, but analyzed with reference to recent studies conducted on the multiaxial behavior of ice.
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.
A one-dimensional rate-sensitive stress-strain relationship is developed to describe the uniaxial mechanical behavior in compression for sea ice. It is a one-term, nonlinear model and is simpler in form than the nonlinear models proposed by other investigators. It contains four independent constants that are determined by experimental data. This model can describe the behavior of sea ice very well under constant strain rate loading, constant stress rate loading and creep loading conditions. In particular, it describes the following features of sea behavior: 1 the increase in ice strength with strain rate and with stress rate; 2 the increase in strain-softening effects with strain rate; 3 the relative difference between the strengths obtained by constant stress rate and constant strain rate tests; 4 the rate dependence of ice stiffness; 5 primary, secondary, and tertiary creep, where the duration and rate depend on the applied stress level. This paper presents the proposed rate-sensitive stress-strain relationship and discusses its behavior under various loading conditions. A set of coefficients has been selected to compare with test results under constant strain rates. Agreement between predicted and observed stress-strain behaviors is very good. Predicted behavior under constant stress rate and creep are also presented.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.