Study On The Mechanical Properties Of Ice In Main Heilongjiang River And Analysis On The Influencing Factors Of The Impact Of Drift Ice On River Beach

In the extremely cold region of northern China,the winter temperature is low and lasts for a long time,and stable ice sheet often appear in the river channels.With the arrival of spring,the ice sheets in most water areas thaw and rivers open,resulting in a large amount of drift ice.Under the action of the rising water level and other factors,the drift ice has a high kinetic energy,which will pose a great threat to the river beach and the bridge in the river,and bring harm to the production and life of people on both sides.This paper mainly explores the relationship between the uniaxial compression strength of river ice and strain rate and temperature,and analyzes the methods to obtain the distribution density and velocity of drift ice during the spring opening period,as well as their effects on the impact of drift ice on the river beach.The specific research contents of this paper are as follows:(1)Four temperature values of-10?,-15?,-20?and-30?were selected.Under the condition of wide strain rate of 10^-7s^-1?10^-1s^-1,the unconfined uniaxial compression strength test of river ice was carried out by cryoelectronic universal testing machine to analyze the relationship between uniaxial compression strength of river ice and strain rate and temperature.(2)During the spring river opening period,the camera was used in the field to shoot the target river reach at a fixed point.Matlab simulation software was used to program,and the brightness equalization processing was carried out on 432 sample images through the top-hat transformation algorithm.The optimal threshold value was selected based on OTSU algorithm to perform threshold segmentation on the sample images and calculate the drift ice distribution density.The influence of convective crest impact probability on river beach under different distribution densities is studied.(3)The field drift ice velocity was obtained by GPS locator,and the drift ice size was obtained according to the field observation data.According to the undisturbed soil collected in the field area,the soil sample data of indoor model test was determined,and the soil river beach model was established in the low-temperature laboratory.The similarity criterion of laboratory test model was established to determine the drift ice velocity and test size.The impact process of the drift ice impacting the river beach in the field is simulated by indoor model test,and the influence of different drift ice velocities on the impact force of the drift ice on the river beach is analyzed.The results showed that:(1)At the same temperature,the uniaxial compression strength increases and then decreases with the increase of strain rate.When the strain rate is in the range of 10^-2?10^-1,it does not change any more.There is a good power function relationship between uniaxial compression strength and strain rate,and the fitting effect of brittle zone is better than that of ductile zone.The peak value of uniaxial compression strength increases gradually with the decrease of temperature,and moves to the lower strain rate.(2)The large area drift ice distribution density at the target section occurred after 12:28 on April 30,during which the maximum drift ice distribution density was 75%,until after 14:00 on May 1,the drift ice distribution density was the lowest 2%,and the drift ice was basically over.With the decrease of the drift ice distribution density,the probability of impact between the drift ice distribution density and the river beach decreases,and the decreasing speed gradually accelerates.When drift ice distribution density in the channel is more than 50%,the drift ice is easy to collide with the river beach,which poses a great threat to the river beach.When the drift ice distribution density is reduced to less than 30%,the drift ice will almost never collide with the river beach,and this is the safety interval.(3)Using the similarity criterion of normal model to simulate the impact test of the drift ice,the physical scale which plays a key role in the collision process of the drift ice impingement is deduced.According to the field data collection,the size of the regular and abundant drift ice along the river beach is 3m in length and 1.5m in width,and the drift ice velocity fluctuates in the range of 0.2?3.5m/s.Through the laboratory test of the impact force of the drift ice on the river beach,the impact force of the drift ice gradually increases with the increase of the drift ice velocity,and the two are positively correlated.The fitting formula of the two is y=60.089x-2.433,and the fitting coefficient R² is as high as 0.93,indicating that the two have a good linear relationship.