Research On Fields Coupling In Saturated Granular Soil Freezing Process

The freezing process of soils extremely complicated involving interactions among thermal, physical, chemical mechanisms. The phenomenon of frost heave can cause severe damage to roads and constructions. Many researchers have paid much attention on the study of frost-heaving mechanism. Many frost heave models were developed. But only several models explained the segregated ice phenomenon, and these models just concerned with 1-D freezing process without stress coupling. This dissertation developed a 1-D numerical model which simulated ice segregating process in saturated, granular, air/solute-free soil, and developed a 2-D numerical model. Then a simple 1-D model was developed for the heat-moisture-stress coupling behaviors of saturated, granular soil. The main contributions are as follows:Based on the conservation of forces and energy and O'Nell & Meller' theory, a new 1-D numerical ice segregating model was developed for coupled moisture and heat transfer process in saturated, granular, freezing soil. In this model, the driving potential of unfrozen water and the criterion of segregated ice initiation were modified. Then the partial differential equations were solved by FDM, The calculate results were compared with the experimental data and observations. The simulation result showed that ice layers could be formed when ice segregate continuous.Different freezing processes with different boundary conditions and soil properties were simulated, and the influence of parameter in the model to the freezing process was analyzed. The simulation result showed that the load, the temperature change rate at boundary, the hydraulic conductivity, and the water-holding ability of soil influenced markedly the frost heave phenomenon.Based on the 1-D ice segregating model, a simple 1-D model was developed for the heat-moisture-stress coupling behaviors of the saturated granular soil. The control equations were then solved by Duhamel method, and the influence of different force boundary conditions on the frost heave phenomenon was analyzed.A method to calculate the ice velocity (rate of heave) in 2-D freezing process was developed, then a 2-D ice segregating numerical mode was derived from the 1-D model, and analysis of the influence of different temperature boundary conditions on the frost heave phenomenon was conducted.The freezing process of two types of saturated, granular, porous media was studied by visualization method. The experiment results showed that near the unfrozen region ice was congregated in the frozen region.Results of the model were compared with experimental results under similar boundary conditions and soil properties and good agreements were obtained.