Study on Frost Heaving Characteristics of Turf Soil in Seasonal Frozen Region

Based on the freezing damage of turfy soil in the northeastern China through the line engineering, the samples of turfy soil in the typical distribution section were collected on site. Taking several factors such as temperature, water ratio, organic content, degree of decomposition and porosity into consideration, laboratory experiment was done to test the frost heave coefficient of the soil sample, and thus obtaining SEM images of soil samples at different water ratio, organic content, degree of decomposition and density of various under different temperatures. After correlation analysis, the sensitivity order of various factors affecting the frost heaving of turfy soil (from big to small) is water ratio, organic matter, porosity and degree of decomposition. And the lower the temperature, the smaller the influence of each factor on the frost heaving rate. The frost heaving rate of turfy soil is positively correlated with water ratio and organic matter, at the same time negatively correlated with porosity and organic content. It can be seen from the microscopic images of turfy soil with different decomposition degrees that the layered structure of the turfy soil is very obvious, and the microstructure is loose, while there are a lot of pores in the samples. Through Image-Pro-Plus analysis, the porosities of the soil sample increase with the add of the organic content when they have the same water ratio range; while the water ratio has a relatively small effect on the porosity within the same organic content range.