Research And Application Of Frost Heaving Mechanism Of Seasonal Frozen Soil

Frozen soil is special, which contains kinds of soil with ice below minus or zero Celsius degree. According to the existence time's length, it is divided into two kinds which are permafrost and seasonal frozen soil. In China there is seasonal frozen soil occupying 5.137 million km2, 53.5% of total China areas at north latitude 30°northly. Frozen soil is special soil-water system containing ice crystals, which is multiphase complex consisting of solid particles, ice, liquid water and the air. The existence and evolution of frozen soil make sense to human living environment and development because there always are natural resources such as land, forest, minerals and so on in frozen soil region. So it is of great significance to study frozen soil thoroughly. Soil frost heaving as result of segregation frost swelling during freezing in cold region, makes damage to the buildings above. This paper takes research on the interaction between engineering and frozen soil environment and mechanism of frost heaving, and obtains the conclusion and proposal for engineering construction stability and controlling measures. This paper is divided in to five parts.The first part generally introduces the distribution of frozen soil and research significance, and the development, trend of research in details at home and abroad. The frost heaving mechanism is the important point in this part.The second part introduces the forming reason, relationship between frozen soil and local natural conditions, nine forms of water in frozen soil, microstructural features of seasonal frozen soil, phase to phase contacting situation, and physical and chemical analysis on seasonal frozen soil. In addition, it further discusses those effects to frost heaving properties, which comes from granularity, density, water content, temperature gradient, and humidity gradient of frozen soil and presents heat exchange coefficient, hydraulic parameters and formulas. The third part takes a further research on capillary theory used in granualar soil, the second frost heaving theory used in clay, and segregation frost heaving theory used as complementarity of the two above. The different theories are generally the same on effect factors to frost heaving despite of different mechanisms existing. The segregation frost heaving occupies the main size of saturated soil in open system. The segregation frost heaving is composed of two physical processes which are water migration and ice-formed effect in soil. Heat flow and water flow situation are the leading factors that determine soil mass frost heaving, while soil nature, solute's components and contents, and external pressure will change frost heaving intensity and speed to different exten. This paper explains the whole frost heaving process supported from experimental data in Changchun the typical season forzen region, where the average frozen depth is 1.5 m, ice lens'thickness is 1.1～1.5 m, and the water migration rate acounts for 3.3～4.5% that increases as water content.In the fourth part it builds frost heaving prediction model based on the heat equation, void-water pressure equation and mass equation, and puts forward several controlling frost heaving measures according to acquired results of mechanism research in the third part, practical experiences, predecessors'achievements.It is the conclusion and proposal in the fifth part, which provides reliable references for practical engineering based on deep research results in the four parts above.