Coupled Analysis Of Water And Heat Under Freezing And Thawing Conditions Of Soil Slope In Seasonal Frozen Area

The soil samples used in the experiment were taken from the test section of the 54 km section of Wunan in the “Northern Leading”.On the basis of the soil freeze-thaw damage test,the slope of the test chamber was simulated by the low temperature environment on the premise of 1:225.The model test completed the freezing and thawing cycle test of the remodeling soil slope in a certain temperature mode.The slope top,slope,3/4 H slope,1/3H slope were analyzed before freezing,maximum freezing depth and temperature after melting and moisture change.The numerical simulation of the same size slope model was carried out by using COMSOL.Through the coupling analysis of the temperature field and water field under the freezing-thawing-seepage of the soil slope in the seasonal frozen zone,the freezing-thawing-seepage of the channel slope in the spring flooding period was obtained.The process of temperature field change of water field.The main results of the following four aspects have been achieved:(1)Through the soil freeze-thaw damage test.The thermal conductivity decreases linearly with the increase of the number of freeze-thaw cycles.When the 7th freeze-thaw cycle is reached,the decreasing trend gradually decreases,and the thermal conductivity decreases from 1.389W/(m3·k)to 1.135 W/(m3·k).The reduction is 18%,and the thermal conductivity gradually approaches a certain stable value after 11 cycles.With the increase of the number of freeze-thaw cycles,the permeability coefficient gradually increases.For samples with dry density ?=1.55g/cm3 and water content ?=22 %,after 6 freeze-thaw cycles,the permeability coefficient tends to increase the stable overall value 3 to 5 times.At the same number of freeze-thaw cycles,the permeability coefficient decreases with increasing dry density and moisture content.During the freeze-thaw cycle,the porosity of the sample increases and the dry density decreases.(2)Through the experimental study of the slope freezing and thawing model,the variation law of the temperature field inside the slope is:During the freeze-thaw cycle,the 0 ? C isotherm development trend of different parts of the channel is similar,and the frozen-deep development line of the slope is relatively lagging behind the slope;the temperature field of the slope temperature field can reach steady state and stabilize after the whole freeze-thaw cycle The tangential direction along the slope is linear;the temperature field changes and the soil temperature change with time are basically the same.The calculation results at different stages indicate that the correlation between soil temperature and temperature is getting smaller with the increase of soil depth,indicating the relative lag of soil temperature to temperature fluctuation atdifferent depths.During the freezing process,the whole water migrates to the frozen front,the water content of the shallow layer increases,and the water in the vertical direction is redistributed.During the melting process,the water migrates downward and the water content of the melted layer increases.Comparing the water changes at different depths of a whole cycle,it is found that after the completion of a freeze-thaw cycle,the water inside the slope gradually reaches equilibrium,indicating that the water migration of the sample is basically the same during the freezing and melting process.(3)Using COMSOL to establish the original size slope model and numerical model test to simulate the effect of water infiltration during spring flooding on the melting process of the slope,the results show that the seepage on the slope surface accelerates the melting process,after the start of the freeze-thaw cycle 30.1 h An ice-water mixing zone appears.Due to the infiltration of the slope surface,the water content on the upper surface increases rapidly,and the water content of the lower surface does not change,which proves that the permeability coefficient is low and the water permeability is low.With the increase of time,a supersaturated seepage zone gradually appears inside the slope,which is likely to cause the occurrence of slope landslide when the seasonal frozen soil area melts in spring.(4)Comparing and analyzing the laboratory model and numerical simulation,the test temperature and the simulated temperature can be well matched;the time required to reach the maximum freezing depth,the laboratory test reaches the maximum freezing depth,and the maximum frozen depth simulation value is greater than Measured value;compared to the entire test and simulation process,the overall temperature error is within 2?.From the perspective of temperature requirements,because the trend is more important for temperature changes,this margin of error is acceptable,so the error meets the requirements.