Study On The Characteristics And Damages Mechanism Of Dispersive Soil In Seasonal Frozen Area

Dispersive soils are distributed widely in the seasonal frozen area,including the Songnen Plain in the northeast China,the northwestern United States and along the Mississippi River,and the south-central Canada.Dispersive soil is a clay with its own unique properties.Due to the ions isomorphous substitution in the soil particles,the calcium and magnesium ions are replaced by sodium ions,which increases the adhesive water thickness on the surface of the soil particles.The repulsion force between the soil particles is greater than the Van der Waals force,which makes the soils have the dispersibility property in lower salt water.In order to ensure food security and revitalize the economy northeast China,the government has built a large number of roads and water conservancy projects with the dispersive soils in the Songnen Plain.The dispersive soils have caused a large number of engineering accidents in hydraulic engineering,road engineering and building foundation projects.The deterioration actions of climatic factors change such as freeze-thaw cycles,groundwater and rainfall soaking on dispersive soils make the damages of dispersive soils engineering more obvious in seasonal frozen areas.The damages characteristics of dispersive soil are concealment,suddenness,and difficulty to manage.A large number of dispersive soils damages have caused significant economic and property losses to the country,and even threatened the people's lives.Studying the damages mechanism of dispersive soil in the seasonal frozen area is great significance to improve the quality and safety of the projects.Although domestic and foreign researchers began to study the damages mechanism and engineering treatment of dispersive soils in the 1960 s.However,there is still a lack of overall understanding of the form and characteristics of the damages.The researchers only focus on the erosion and piping in the non-season frozen area,and the research on engineering damages caused by factors such as freeze-thaw cycles,groundwater,rain and soaking is still insufficiency.In seasonal frozen area,there were its own unique damages forms of dispersive soils in addition to all damages forms in the non-seasonal frozen area.Based on the phenomenon of engineering damages,this article summarizes the damages forms and characteristics of dispersive soils in seasonally frozen regions.The characteristics,causes,and inducement mechanism of three types of damages forms,including freeze-thaw cycles damage,freeze-thaw-water immersion deformation damage,and slope landslides instability damage are researched.It reveals the damage characteristics of dispersive soil in the seasonal freezing area,and clarifies the cause and inducement mechanism.The main point on the works and results are listed as follows:(1)We have summarized the damages forms of dispersive soil in seasonal frozen area,pointed out that agricultural irrigation was an important factor in the formation of dispersive soil,and clarified the factors affecting the damages of dispersive soil in seasonal frozen area.(2)Through self-designed experiments,the hydrothermal characteristics and freeze-thaw cycles deformation laws of dispersive soils are put forward,and the cause of freeze-thaw cycles damage of dispersive soils in seasonal freezen area is explained.(3)Through self-designed freeze-thaw-immersion compression deformation characteristics test,the deformation laws and damage mechanism of dispersive soil under freeze-thaw and soaking are clarified,and the calculation method of compressive deformation of dispersive soils under freeze-thaw and soaking conditions is proposed.(4)The instability damage types of dispersive soil landslides in seasonal freezen areas are clarified.Through systematic tests,the characteristics of shear strength of dispersive soils in seasonal freezen areas are proposed,and the instability process and inducement mechanism of landslides in dispersive soil slopes in seasonal freezen areas are revealed through numerical simulation.