| Ice load is one of the important control load in the design of hydraulic and marine structures of cold area. The uniaxial compression strength, fracture toughness and tensile strength of ice is the key parameters in ice load calculation. But ice is a natural composite materials which is very sensitive to the geographical environment conditions, such as hydrology and meteorology, so the physical and mechanical properties of ice have great differences. And the researchers use different test method on the ice from different area, so the test results are also different. It is necessary to study on the physical and mechanical properties of the river ice and fill the blank in the field of ice engineering.Before the experimental study is carried out on the Yellow River ice, at first, we make a observation in Toudaoguai Hydrological station on the Yellow River Ningmeng section. We make a research about the freezing process of Yellow River ice and the formation of ice, as a theoretical basis for sample selection of mechanical test. We find that in the bend of the Yellow River, ice flows and ice flowers accumulate on the outside of the bend because of the centrifugal force. As the ice frozen, the outside of the bend is filled up with ice flows and ice flowers, and the main watercourse move to the inner side of the bend. And it leads to that outside is granular ice, and inner side is columnar ice. And then measure the ice sheet thickness on the open water surface. We find that the bottom of the ice sheet on the open water surface is not flat, but like a parabola. It is because the vortex exist in the flow and it makes the ice sheet in downstream thinner than the ice sheet in upstream.We take ice from the inner side of the bend and make the horizontal and vertical section to determine the crystal structure of Yellow River ice. At the same time, we calculate the average diameter in equivalent diameter method, and we measure the basic physical properties, such as distribution of bubbles in the ice, sediment concentration and density of ice. And then we cut the ice for test samples and transport to low-temperature laboratory of Dalian university of technology by air transportation, In the low-temperature laboratory, we use ice sample cutting instruments to make Brazilian disk. Then we use pressure testing machine equipped with high precision constantly low temperature experiment box to conduct Brazilian disk splitting test to get the tensile strength and fracture toughness of Yellow River ice.Choosing different temperatures and the strain rate keeping the brittleness of ice as a condition for the Brazilian disk splitting test, we selectively analyze the influence of different factors such as strain rate, temperature and Brazilian disk size to the tensile strength and fracture toughness of Yellow River ice. Results of the test indicated that the tensile strength of ice is sensitive to strain rate. The tensile strength also have a close relationship with temperature. Under the same strain rate, the tensile strength of ice increase with the decrease of the temperature. This article also discusses that the changing of disk size effects the tensile strength of Yellow River ice. As the sample diameter increases, the tensile strength of ice decrease. Fracture toughness also has obvious correlation with strain rate. If strain rate was lower than 9×10-4 s-1, fracture toughness of Yellow River ice is constant, but if strain rate was higher than 9×10-4 s-1, fracture toughness of Yellow River ice decrease with strain rate increase. Maximum of fracture toughness increases with the temperature decrease, but the disk size has no effect on fracture toughness. |
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