| The opening of the Inner Mongolia reach of the Yellow River is the focus of the prevention and control of ice flood disasters in China.Various mechanical properties of ice are the basis of ice disaster prevention.As a heterogeneous polycrystalline material,the fracture performance of Yellow River ice is affected by many factors such as its own structure and external environment.In view of this,this paper carried out experimental research on the microstructure and fracture performance of the river ice during the freezing period of the Yellow River in Inner Mongolia,quantitatively analyzed the distribution of the ice crystal grains of the Yellow River,studied the fracture process of the Yellow River ice and the influencing factors of fracture toughness,and determined the two factor fitting surface of the fracture toughness of the ice.Which provided data basis for prediction of river ice breakup and ice force calculation.The main research contents and results are as follows:（1）Quantitative analysis of the microstructure of the Yellow River ice.Taking the ice blanks collected from the Inner Mongolia section of the Yellow River as the research object,the structure characteristics of the ice crystal grains of the Yellow River were extracted and quantified by digital image processing,and the size distribution of the ice crystal grains of the Yellow River was analyzed,and the ice density and mud content of the Yellow River were analyzed.The results show that the equivalent diameter of the Yellow River ice crystal grains is between 0.05mm and46.40 mm,and with the increase of depth,the average equivalent diameter of the crystal grains increases from 3.51 mm to 11.52 mm;the density of the Yellow River ice increases with the increase in depth.The mud content in the surface layer reaches1.8×10-3g/cm3,and the lower layer is always less than 0.4×10-3g/cm3.（2）The Yellow River Ice Fracture Performance Test.Using three-point bending beam test and digital image correlation technology,the fracture performance of the Yellow River ice was studied,the fracture morphology of the Yellow River ice was explored,and the effects of temperature,velocity,and crystal structure on the fracture toughness of the Yellow River ice were analyzed.The results show that the opening displacement during the fracture process of the Yellow River ice specimen is significantly greater than the sliding opening displacement,and the failure mode is mainly type I fracture;within the temperature and rate range of this test,the fracture toughness increases with the decrease of temperature and loading rate.Under the same temperature and speed conditions,the fracture toughness of the columnar ice test is 1.25～1.46 times that of the granular ice sample.（3）The two factor fitting surface of the fracture toughness of the Yellow River ice is determined.The structural differences between the Yellow River ice,lake ice and artificial freshwater ice are analyzed,and the quantitative relationship between the fracture toughness of the Yellow River ice and the fracture toughness of other freshwater ice is clarified.The fitting curve between the fracture toughness of the Yellow River ice and the temperature,as well as the fracture toughness and the loading rate is established.The two factor fitting surface of the fracture toughness of the Yellow River ice is established.Through this surface,the real-time fracture toughness of the Yellow River ice can be calculated,which provides a data basis for the prevention and control of the Yellow River ice flood disaster. |
