Water-vaper Migration Of Frozen Coarse-Grained Soil Under The Influence Of Fine Grain Content And Load

Coarse-grained filling for the bottom layer of high-speed railway roadbed in seasonally frozen regions is considered frost heave-insensitive filling.However,during the actual operation monitoring process,a certain degree of frost heaving still occured,which seriously affected the stability and safety of the moving train.Water-vapor migration inside coarse-grained soil may be the main cause of frost heaving.This paper uses fluorescent tracer and digital image processing technology to study the influence of fine-grain content and load on water-vapor migration of frozen coarse-grained soil under open water supplement.(1)Fine-grained soil is a better water-holding material,which is conducive to the migration of water.Therefore,coarse-grained soil with a higher fine-grain content is more suitable for water supply and migration,which causes a larger amount of water supply.However,as the fine content increases,the pores of the coarse-grained soil are filled,blocking the gaseous water migration channel,which is not conducive to the supply of gaseous water and reduces the amount of gaseous water.(2)Increasing the content of fine particles provides a good migration channel for liquid water inside coarse-grained soil,increasing the migration height of liquid water.The frost heaving of coarse-grained soil originates from the volume expansion caused by the internal freezing of fine-grained soil,which lifts up the soil skeleton and forms frost-heaving.Therefore,the higher fine-grained content aggravates the frost-heaving of coarse-grained soil.(3)When the coarse-grained soil is subjected to axial loads,the load promotes the replenishment and migration of external water,causes more replenishment,and makes the proportion of gaseous water supply exceed 50%.Compared with static load,dynamic load produces "pumping effect" which promotes the water supply of coarsegrained soil more obviously.It is especially beneficial to the supply of gaseous water,and the proportion of gaseous water supply exceeds 80%.(4)Increasing the amplitude and frequency of the dynamic load produces a stronger "pumping effect",results in more water recharge for coarse-grained soil,and promotes the migration height of liquid water in the sample.However,the proportion of gaseous water replenishment is about 85%,which is not significantly affected.(5)The static load inhibits the frost heaving of coarse-grained soil,and the dynamic load promotes the frost heaving of coarse-grained soil,and makes the frost heaving of coarse-grained soil last longer.However,increasing the amplitude and frequency of dynamic load inhibits the frost heaving rate and frost heaving amount of coarse-grained soil.