Study On Frost Heaving Characteristics And Analysis Method Of Channel Foundation Soil In Seasonal Frozen Region

The main grain producing areas in China are mainly seasonal frozen soil distribution areas.Irrigation canals are not only necessary irrigation facilities for grain production,but also face damage and even actual effect caused by frost heave.Taking Heilongjiang Province as an example,affected by the cold environment of seasonal frozen soil,the canals in this area are prone to frost heave damage,which leads to uneven deformation of channel foundation soil,cracks and shedding of lining,slope collapse and water seepage and other damage phenomena,which seriously affect the long-term service of channels and reduce the irrigation rate of farmland.Therefore,studying the frost heave of channel foundation soil is of great significance to the prevention and control of channel frost damage.The Song Gan channel in Heilongjiang province covers a wide area and has complex geological conditions.There are great differences in moisture content and fine particle content of the channel foundation soil.In order to prevent the frost heaving damage,the sandy soil is often chosen as the main filling material of channel foundation in seasonal frozen area,but serious frost heaving damage still occurs in local channel foundation,causing cracks or other problems in channel lining.The Song Gan channel is chosen as the research object in this thesis.The mechanism of soil frost heave was clarified,the temperature field,moisture field and frost heaving characteristics of canal foundation soil in the process of frost heave were analyzed after considering the influence of filling water and fine particle content.A frost heaving prediction equation which considers the effects of many factors influence was establised.Based on the finite difference method,the frost heaving process of canal was analyzed,and the general frost heave rules of the canal foundation were revealed.The main research contents and results are as follows:（1）The frost heave mechanism of soil was elucidated,and the basic theory of temperature change and water migration of soil during freezing was revealed.The main parameters of determining frost heave were given,and the basic principle of applying the finite difference method to simulate the frost heave was discussed.（2）The effect of water replenishment on the frost heave of canal foundation was explored.Frost heaving tests were carried out on canal foundation soil with different initial moisture content.The evolution of temperature and displacement field and the moisture distribution were analyed during the freezing process,and the frost heave differences of canal foundation soil under different ways of water replenishment were given.The amount of frost heave in a open system was greater than that in closed system,the ratio between them was 2 to 22.The ratio is inversely proportional to the initial water content of the soil samples.（3）Different ratio of fine grain content was designed to analyze the influence of fine particle content on the frost heave characteristics of canal foungdation soil,and the relationship between the temperature field,frost heave quantity and the fine particle content of canal foundation soil was revealed.With the increase of fine particle content,the amount of frost heave increased firstly and then decreased.When the soil has a fine particle content of 25%,its frost heave deformation reaches the maximum value.When the content of fine particle is the same,the water supply is the key factor to determine the deformation degree of channel foundation.（4）Taken the local temperature data as the temperature application condition,a numerical model of frost heave of channel foundation based on finite difference method was established.The general law of freezing process of channel foundation was given.The temperature and frost heaving of channel foundation were negatively correlated with the depth of channel foundation,and the freezing depth extended downward with time goes by.The freezing depth reached the maximum in February,and the frost heaving deformation was the most significant.The frost heaving deformation of channel slope was slightly greater than that of channel bottom.