Numerical Simulation Of Artificial Freezing Method Induced Soil Frost Heave

Frost displacement is very important to predict the influence to the environment during the article frost construction because it may affect buildings on the earth due to the frost heave by water migration, thus cause a variety of destructions. Yet relative study is quite short. The research results of frost heave mechanisms, numerical predication models and the frost precaution method are summarized in this paper, and the heat transfer model in the frozen soil is formulated. On calculating the frost heave, the water migration content is determined by the relationship between the water influx content and the time, the original water frost displacement is determined by the relationship between the unfrozen water content and the temperature, thus, the emigrant and original water frost displacement is calculated by the thermal stress computing program of MARC in which the volume expantion coefficient induced by freezing is considered as negative thermal expansion coefficient; the total frost heave displacement is the sum of the two displacements, and the influence of the load to the frost heave is taken into consideration by the frost coefficient and load experiential formula. The Finite Element Method is used modelling one-dimension freezing and two-dimension model of artificial horizontal freezing method. Comparing the results of simulation and experimental and field measurements, the error ranges from 10% to 15%, which indicates the method of computing modelling in the paper is feasible. The influence of different covered depths, thickness of frozen wall, excavating radius, original water content and brine temperature on frost displacement are discussed for horizontal freezing model. The results are: The vertical frost displacements of earth surface is maximal at the plane of symmetry, and minish wavely with the increasing of distanace from symmetry plane. While the horizontal frost displacements of earth surface reaches the maximum at a certain distance from symmetry plane, which is direct proportional to the covered depth and weekly influenced by the other factors. The maximal earth surface vertical frost displacements decrease exponentially with the decreasing of the load, and ultimately are constants, and increase more quickly at the beginning with the increasing of frost wall width, then slowe, and expedite again later, and are direct proportional to the excavating radius and original water content, and the curve of them and brine temperatures is a parabola with a downwards hatch, that the slop on the right side is more precipitous than the left. Under the same conditions as above, the maximal earth surface horizontal displacements have the same varying laws as the maximal vertical displacements, but are smaller than them and vary more gently. At the plane of symmetry, the vertical displacements increase with the depth's increasing in the earth outside the frozen wall while decrease inside. According to the results, the suggestions about restraining the frost heave are brought forward. The results have theoretical significance and reference value to the application of the artificial freezing project in the underground engineerings of city.