| The climate in Northeast China is cold in winter,and the hydraulic structures such as canals and reservoirs are gradually frozen under the influence of temperature in winter.The ice cover formed by ice will produce the static ice load which will damage the hydraulic structures.When the ice layer reaches a certain thickness,with the increase of temperature,the ice layer will produce ice temperature expansion force,which will damage the hydraulic structures and the reservoir slope protection,thus affecting the safe operation of the reservoir.In order to study the ice load and the ice temperature expansion force better,using the natural fresh water ice obtained from the reservoir,an important parameter of the ice load,namely the uniaxial compression strength of the fresh water ice,is tested and studied,and the relevant influencing factors are analyzed.The laboratory simulation experiment of ice temperature expansion force was carried out in the low temperature environment simulation laboratory,and the generation process of ice temperature expansion force in the field was reproduced.The relevant influencing factors of ice temperature expansion force were analyzed,and the following conclusions were obtained:(1)The ice sheet formation of the reservoir is affected by many factors in the field.The ice thickness prediction model can be used to predict the change process of the ice thickness.The change of the ice thickness is also one of the main causes of the ice temperature expansion force.The methods of ice breaking and grooving,plastic film sliding,improving slope protection structure,placing ice sinking and discharging,regulating water level and preventing icing can all play a corresponding prevention and control effect on the ice pushing and destruction of the reservoir,and each protection method has its own advantages and disadvantages,which can provide guarantee for the safe operation of the reservoir.(2)The uniaxial compression strength test was carried out on the reservoir fresh water ice,and the ice sample processing and experimental study were carried out on the columnar ice.Different strain rates correspond to obvious ductile zone,brittle zone and ductile brittle transition zone.It can be clearly seen from the extreme value of uniaxial compressive strength of ice and the stress-strain curve that the uniaxial compressive strength of ice increases first and then decreases with the change of strain rate,and there is a power function relationship between the compressive strength of ice samples in the ductile and brittle regions and strain rate.Through four experiments at different temperatures,it is found that temperature is also the main factor affecting the uniaxial compression strength of ice,and temperature has a significant effect on the uniaxial compression strength of ice.The lower the temperature,the greater the peak uniaxial compression strength of the ice.The ductile and brittle transition zone shifted to a low strain rate with the decrease of temperature.At the same strain rate,the uniaxial compressive strength of ice increases with the decrease of temperature,and there is a good logarithmic relationship between the extreme value of uniaxial compressive strength of ice and the absolute value of ice temperature.Due to the anisotropy of columnar ice,different loading directions also have an effect on the uniaxial compression strength of ice.The uniaxial compression strength loaded along the direction of ice thickness growth is significantly greater than that loaded perpendicular to the direction of ice thickness growth.(3)The laboratory model test was carried out in the low temperature environment simulation laboratory,and the change process of ice temperature expansion force was simulated in the laboratory.Through the comparison between the simulation experiment and the field,it can be found that the ice temperature expansion force appears in the spring heating stage,when the ambient temperature is-2.14 ℃,the results of the indoor test are consistent with the field,and the ideal results are obtained,which can provide theoretical support for the field engineering construction.In the later stage of the test,the surface temperature fluctuates greatly due to the increase of the ambient temperature and the addition of light compensation.The ice temperature expansion force increases gradually with the increase of the ice temperature.When the ice temperature expansion force reaches the maximum,the ice temperature is-1.9 ℃.The ice temperature expansion force decreases but the ice temperature is still increasing in the later stage of the test,which indicates that the ice temperature is still increasing Temperature is one of the influence factors of ice temperature expansion force.Through the indoor model test,it can be concluded that the ice temperature expansion force is generated in the heating stage,which first increases rapidly,then slows down the growth rate,indicating that the ice temperature expansion force is related to the temperature rise rate.In the stage of constant low temperature,the expansion force of ice temperature is very small relative to the extreme value,which can be ignored.The distribution of ice temperature expansion force along the vertical direction is that the upper layer is large,the lower layer is small,and the distribution is inverted triangle.In the indoor model test,the maximum ice thickness is 10.65 cm,the maximum ice temperature expansion force is 118.7kpa,and the maximum ice temperature expansion force occurs at 3.5cm.The point of action of the ice temperature expansion force is 1/3 of the whole ice sheet.(4)Through the observation of ice temperature expansion force under different temperature rise rates under linear temperature control conditions in the simulation laboratory of low temperature environment,it can be seen that the ice temperature expansion force is greatly affected by the temperature rise rate,and the ice temperature expansion force tends to increase first and then decrease as the temperature increases,and the faster the heating rate is,the greater the ice temperature expansion force generated.Laboratory simulation can be used to control variables,and the generation and change of ice temperature expansion force under different ice thickness and different initial temperature conditions are obtained.It is found that the expansion force of ice temperature is related to the ice thickness and initial temperature.A relatively low initial temperature will generate a large ice temperature expansion force.For different ice thicknesses,the ice sheet is relatively thin and sensitive to temperature,so the process of generating ice temperature expansion force is relatively early,indicating that heat is transferred from the top to the bottom in the ice.The thicker the ice is,the larger the ice temperature expansion force is. |
