Moisture Changes And Influencing Factors Of Unsaturated Loess Subgrade Under Atmospheric

This paper mainly took Malan loess subgrade in Northwest China as the research object to rain under atmospheric effect- evaporation of subgrade humidity and temperature fields and cyclic deformation mechanism of action for research purposes; through laboratory tests physical and mechanical properties, artificial filling model tests and finite element analysis and other means to carry out a comprehensive rainfall- action evaporated under cyclic unsaturated loess subgrade slope soil moisture, temperature, pore water pressure and the dynamic response of law and stability of deformation; and were different atmospheric conditions, changes of subgrade soil moisture and temperature fields and influencing factors were analyzed. The main contents and results are as follows:First, it summarizes the basic theory of the existing unsaturated loess, evaporation and infiltration theory, and lay a solid foundation for the theory test and numerical simulation below; fill soil samples for the selected unsaturated loess were indoor physical characteristics test grading curve determined by its physical and mechanical parameters of the optimum moisture content, maximum dry density, liquid plasticity index, permeability coefficient, prepare for the next model tests and numerical analysis.Secondly, the rainfall evaporation model test of the unsaturated loess subgrade slope was designed and carried out, to simulate the different atmospheric effects on the influence of the subgrade and record the changes of moisture content, temperature and displacement of subgrade model under different atmospheric conditions; It was found that in the rainfall infiltration process, the unsaturated loess subgrade slope corresponded to a critical infiltration intensity; The change of moisture content in the surface soil of the roadbed side slope was obvious; Moderate rain in the depth of influence on the subgrade soil moisture changes was the largest; Different location of the subgrade soil moisture content were affected in different levels; The infiltration rate of water in unsaturated loess subgrade was greater than that of evaporation rate.Finally, on the basis of indoor physical characteristics test and model test, by unsaturated soil seepage analysis software Geo-Studio, the variation law of soil moisture content, soil temperature and pore water pressure of unsaturated subgrade loess slope under rainfall infiltration and sunshine evaporation were simulated.It is found that the negative pore water pressure of the soil is negatively correlated with the time of rainfall and the intensity of rainfall; Under the same sunshine time, the soil temperature of the slope was the maximum rise;The change of humidity field affected the soil temperature, showing that the soil moisture content was increased and then the variation of soil temperature was reduced, and the influenced depth of the subgrade temperature field was increased by the atmospheric temperature.Atmospheric effect on circulation mechanism of loess roadbed slope was a very complex problem.Although this paper has done a lot of work, but it was limited by the level of unsaturated soil theory development, test conditions and research methods, while there were some differences between the model tests, numerical simulation and the actual atmospheric effects. Those problems may lead to some errors in the testing process. Accordingly, to reveal the influence of atmospheric effects on subgrade humidity, there is still a long way to go.