The Simulation Of Soil Freezing Process By Thermal Lattice Boltzmann Methods And Experiment Research

In these years, our country has regarded the soil freeze-thaw problems as one of themost important subjects of cyopedology, because the problems turn out to be more andmore important which include railway and highway security, infrastructure maintenanceand metro construction problems. In the subject, the research of the soil temperaturedistribution, the frozen time and the moisture dispersion in the soil freezing process playan important role in the road construction and engineering application. And it is verydifficult to solve the problems for the reason that the thermal transmission equations arenonlinear by macro approach. However, the Lattice Boltzmann can solve the nonlinearequations in a much easier and more efficient way and it will become one of the mainmeans to deal with the Mesoscopic problems.This paper mainly does the research about the one-dimensional unsaturated soilfreezing process under different simulation conditions by Thermal Lattice BoltzmannMethods, finally achieves the result parameters that include soil temperature distribution,the frozen time, the freezing time and the moisture dispersion. What is more, a soilfreeze-thaw test bench with the height of2m has been built, and the test ofdetermination of basic parameters which include the density has been completed, theinitial moisture, the porosity and the distribution of the soil particles size. In addition,this paper comes up with the experiment procedure and scheme for the further researchcontents based on the test bench. And the soil temperature distribution and the unfrozenwater content variation in different depth are tested under the condition that thecold-side temperature is-12oC.The results show that (1) Compared with the approximate solution and theexperimental result, the one-dimension soil freezing process can be simulated correctlyby the Thermal Lattice Boltzmann Models.(2) The duration of the soil rapid freezingstage will be relatively shorter if cold-side temperature is lower, and Temperaturemutation exists near the phase interface because of its mobility.(3) The less initialmoisture content and the smaller dry density will make soil thermal diffusion coefficientsmaller and the phase interface will move more slowly.(4) Compared with the initialmoisture content and the density, the cold-side temperature has a larger influence on the soil temperature distribution and the frozen time.(5) The periodic freeze-thaw controlmodel affects the soil average temperature a bit, but it has a large influence on thesurface temperature.(6) Because of the porosity, different soils have differenttemperature after frozen in the same depth, and the gravelly soil which has the smallestporosity is coldest, then the loess follows, and the loam has the highest temperature.(7)For the seasonal silty clay, this paper puts forward Empirical formulations between thefrozen time and the freezing time with several parameters such as the cold-sidetemperature, moisture content and density by software Minitab.(8)The experimentalresults show that the soil temperature and the moisture content are different at thedifferent location of the same height. As time goes on, the soil temperature of differentdepths gradually decreases, but the moisture content does not change.