Flexural Strength of Lake Ice in Relation to Its Growth Structure and Thermal History.

• Main Authors: Gow,Anthony J., Langston,David
• Other Authors: COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER N H
• Format: Text
• Language: English
• Published: 1975
• Subjects: Snow; Ice and Permafrost; *ICE; GROUND LEVEL; TEMPERATURE; CRYSTAL STRUCTURE; STRUCTURAL PROPERTIES; STRESS TESTING; CRACKS; ATMOSPHERIC TEMPERATURE; FIELD TESTS; ORIENTATION(DIRECTION); TEST METHODS; FLEXURAL STRENGTH; FAILURE(MECHANICS); LAKES; CRYSTAL GROWTH; Ice; permafrost
• Online Access: http://www.dtic.mil/docs/citations/ADA020964; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA020964

In-place cantilever beam tests on Post Pond and Mascoma Lake (N.H.) ice yielded a maximum flexural strength of 7.1 kg/sq cm. The minimum strength, unrelated to failure along pre-existing cracks in the ice, was 2.9 kg/sq cm. The majority of tests were performed in the push-down mode after it was discovered that beams tested in the pull-up mode, which places the bottom surface in tension, frequently broke prematurely along cracks in the bottom of the ice. Premature failures of this kind usually occurred at stresses of 2-3 kg/sq cm. Data further demonstrate that the intrinsic strength of lake ice decreases sigificantly as the surface air temperature goes to 0 C. Ice that has just become isothermal, but has not yet begun to candle, has a strength of about 4 kf/sq cm; ice that has been subjected to prolonged periods of above-freezing air temperatures generally fails at about 3 kg/sq cm. Tests also show that cold unrecrystallized snow-ice is as strong as the underlying lake ice. Tests of the effect of crystalline structure indicate that ice composed of crystals with their c-axes horizontal is measurably stronger than ice in which the crystals are oriented with their c-axes vertical. (Author)