Experimental Study On Frost Heave Characteristics Of Loess And Normal Frost-Heave Force

China's seasonal frozen land area is vast,accounting for 53.5% of the land area,seasonal frozen land area is widely distributed in the loess.Frost heave in loess area is a complex problem,and there are many factors affecting it,which can be divided into internal and external causes.Among them,internal factors include grain size distribution,mineral composition,salt content,water content and dry density of soil,and external factors include external load,environmental temperature,surrounding water supply conditions,etc.The more the frost heave of soil is restrained,the greater the frost heave force acting on buildings when soil is frozen.In the engineering of foundation,subgrade,tunnel and culvert,the frost heave force of loess will lead to different degrees of deformation and cracking of the structure,and even cause structural damage.This will lead to serious security problems and economic losses.In this paper,the frost heave characteristics and frost heave force of loess are studied.The frost heave characteristics of soil samples with different moisture content and density were studied under different loads.The frost heave forces of soil samples with different moisture content and density under different freezing temperatures were studied.The relationship between frost heave rate and water content,density and load of loess is revealed by experimental study on frost heave characteristics.The frost heave rate of soil sample under lower upper load decreases greatly compared with that under natural condition.As the load continues to increase,the effect of load increment on frost heave suppression decreases.With the increase of load,the frost heave rate decreases exponentially.Under the condition of free frost heaving,the frost heaving rate of loess samples varies greatly with the dry density.The frost heaving rate of loess samples changed little with the dry density after loading.The larger the moisture content of soil sample is,the greater the change of frost heaving rate with dry density is.For the same density soil sample,under the same load,the water content and frost heaving ratio of soil sample are approximately linear.The frost heaving rate increases with the increase of water content.When the load level is high,the frost heaving rate increases with the increase of water content,but the increase range decreases significantly compared with the free frost heaving.Among the factors affecting frost heave in Loess area,load has the greatest influence on frost heave,followed by water content and minimum dry density.The frost heave prediction model considering the effects of moisture content,dry density and load was obtained by fitting the test results of soil samples with different moisture content and dry density under different loads.Through comparative analysis,the rationality of the model is verified.The frost heave force tests of loess samples with different moisture content and dry density were carried out at different soil temperatures.The results show that the frost heave force of loess is closely related to soil moisture content,dry density and temperature.When the soil temperature is higher,the frost heave force increases greatly with the decrease of freezing temperature.The increase of frost heave force decreases with the decrease of soil temperature.The initial moisture content and dry density of soil samples are larger,and the frost heave force increases more when the soil temperature decreases.When the soil temperature is constant,there is a minimum water content in the soil sample,which is lower than the water content.When the freezing deformation of the soil sample is restrained,no frost heave force will be produced.With the increase of initial water content of soil sample,the increase rate of frost heave force of soil sample increases.When the moisture content and temperature are fixed,the higher the dry density is,the faster the frost heave force increases.Among the influencing factors of frost heave force in Loess area,dry density has the greatest influence on frost heave force,followed by water content and soil temperature.Further fitting the test results,the frost heave force model considering the effects of water content,dry density and soil temperature was obtained.