STUDY ON THERMAL ICE STRESSES OF A POND IN COLD REGION

Static ice pressure due to thermal expansion is a key parameter for the design of hydraulic structures in cold regions. Thermal ice stress is affected by various factors, including thermal conditions of ice sheet (ice temperature, temperature rise rate, etc.), ice sheet constraint conditions, ice sheet thickness, etc., which leads to uncertainties in the estimation of thermal ice stress. To investigate the spatial and temporal distribution of thermal ice stress, a prototype observation was conducted to No.6 pond of Qinghuahu lake in Daqing City, Heilongjiang Province, and the ice temperature and thermal stress were fully analyzed. The analysis results indicate that ice temperature mainly depends on the fluctuation of air temperature, and that the ice temperature of each layer fluctuates more gently with time than air temperature. With the increase of ice depth, the fluctuation range of ice temperature decreases, and ice temperature increases. The surface ice temperature is well linearly related with air temperature by the change rate between 0.38 and 0.56, and the influence of air temperature on ice temperature is quite obvious within 30 cm, and ice temperature below 30 cm presents a linear distribution along depth. Based on Bergdahl's rheological constitutive relation of static ice, a mathematical model of thermal ice stress is proposed. The undetermined parameter in the model is determined by regression combining with measured data, and its values obviously depend on measuring positions. The calculated values of ice stress agree well with the measured ones. From station 1 to station 4, the overall thermal ice stresses increase. The stress is non-monotonically distributed along ice depth, i.e., thermal stress in surface ice is slightly smaller, reaches a maximum at the depth of 10~30 cm, and then gradually declines with depth. Moreover, thermal ice stresses only appear on the upper part of the ice within 0.7 m.