DYNAMICAL COMPRESSIVE STRENGTH AND FAILURE OF NATURAL LAKE ICE UNDER MODERATE STRAIN RATES AT NEAR MELTING POINT TEMPERATURE

Abstract

THIS PAPER PRESENTS A SERIES OF UNIAXIAL COMPRESSIVE EXPERIMENTS ON NATURAL LAKE ICE UNDER MODERATE STRAIN-RATE IN THE RANGE OF 10−1 TO 102 S−1 AT −0.1 °C. NATURAL LAKE ICE SAMPLES OF 8 CM BY 8 CM IN CROSS SECTION AND 20 CM HIGH WERE USED TO INVESTIGATE STRAIN-RATE DEPENDENCE OF UNIAXIAL COMPRESSIVE STRENGTH AND FLAW EFFECTS ON ICE STRENGTH UNDER MODERATE STRAIN RATES. THE FRACTURE MODES OF ICE AT MODERATE STRAIN RATES WERE ALSO SYSTEMATICALLY INVESTIGATED BY USING HIGH-SPEED CAMERA. IT IS FOUND UNIAXIAL COMPRESSIVE STRENGTH OF NATURAL LAKE ICE INCREASES WITH INCREASING STRAIN-RATE IN THE EMPLOYED MODERATE STRAIN-RATE RANGE. AND NATURAL FLAWS SUCH AS AIR BUBBLE HAVE A SIGNIFICANT EFFECT ON UNIAXIAL COMPRESSIVE STRENGTH OF ICE UNDER MODERATE STRAIN-RATE, HIGHER AIR CONTENT ICE POSSESSES LOWER COMPRESSIVE STRENGTH. ICE FRACTURE MODE DEPENDS ON STRAIN-RATE (OR COMPRESSIVE VELOCITY) OF ICE SPECIMEN, VARYING FROM SPLITTING AT STRAIN RATES LOWER THAN 10 S−1 TO CRUSHING AT STRAIN RATES HIGHER THAN 10 S−1. ICE SPECIMEN CRUSHES INTO FINE FRAGMENTS MAY DUE TO INSUFFICIENT TIME FOR MICRO CRACKS TO PROPA-GATE, THUS RESULTS IN HIGHER STRENGTH. IN ADDITION, DEPENDENCY OF COMPRESSIVE STRENGTH ON STRAIN-RATE IN A WIDE STRAIN-RATE RANGE IS ALSO DISCUSSED.