Experimental Study On Uniaxial Compressive Strength Of Fresh Water Ice

As the solid state form of water, ice is wide spread in nature. For the high latitude areas and countries, ice is a kind of element which must be considered in the design and management of water conservancy engineering. And the uniaxial compressive strength, as one of the key parameters of ice mechanical properties, is necessary to design the structures related to water. Meanwhile, the uniaxial compressive strength is a complex parameter which influenced by many factors, including ice crystal, air bubbles, temperature, and even the test method. Compressive strength is a basic ice mechanical property. Experimental study on uniaxial strength can not only be used in the design of many ati-ices structures, but also contribute to find the essence characters of ice, with both theoretical and practical value.In order to study the relationship between uniaxial compressive strength and the factors of influence, we took some nature fresh water ice sample from a lake of Harbin in December,2011. First, full section of the ice was made to observe air bubbles distribution and shapes; horizontal and vertical sections were put on fedorov stage to identify the type and size of crystals. After the investigation, experiment plan was made and adjusted. Finally,5kinds of sample size,5×5cm2,7×7cm2,8.5×8.5cm2,10×10cm2and12×12cm2,2kinds of loading direction, horizontal and vertical,25series, in total385ice samples were made to test at the strain rate from0.0072mm/min to387mm/min.375test results were available.By the uniaxial compressive-strain rate curves, we found that as the strain rate increasing, the maximum stress increased first, and then decreased. Different strain rate also lead to different damage forms:when the strain rate was low, the ice sample would deform plastically with little cracks. Then more and more cracks appeared and the sample would split or swelled as the strain rate rose. When the strain rate was pretty high, brittle damage forms with diagonal planes or step profiles, or broke into small pieces were frequently observed. From the summary of peak uniaxial compressive strength, strength of samples loading in vertical direction was about1.87to2.4times of the ones loading in horizontal, which indicated obvious anisotropic property of ice. Sample size was another factor to influence the compressive strength. Uniaxial compressive strength would decrease as the volume of the ice sample became larger. But the peak compressive strength, of both horizontal and vertical loading ways, changed little when the sectional area was greater than49cm2. And this indicated that the standard ice sample size,7×7×17.5cm3, was suitable to use for the test of fresh water ice in northeast reservoirs and pools of China. The influence of bubbles could be reflected by the density of the samples. Peak compressive strength increased as density increased, especially clear on vertical loading samples. By established the scatter diagram of peak compressive strength, sectional area and porosity, well relation between these three parameters were found and could be expressed by formula.