Study On Moisture Migration Of Compacted Loess Based On Soil Water Potential Theory

The distribution of loess in China is wide and thick,In the loess areas are four distinctive seasons,precipitation concentration,and the diurnal and annual ranges of temperature are larger,the change of precipitation and temperature will cause the obvious moisture migration in loess.Water transfer will result in the change of soil water content,which will affect the shear strength of the soil,and eventually lead to a series of diseases,which seriously threaten people's production and life.Therefore,it is of great significance to study the law of soil water movement in unsaturated loess,especially in compacted loess of engineering.The basic properties of the first to carry out the indoor test soil test proved that,shear strength and cohesion decreases with the increase of water content of the sample,and increases with the increase of dry density,dry density increases with the shear strength is more sensitive to changes in moisture content,and moisture content and dry density change for effect of cohesion to the internal friction angle is obviously.Secondly,this paper presents a new method of "double vibration and standard splicing",which can obtain more accurate and uniform dry density samples.Then,using the self-made equipment to carry out the indoor experiment study of gravitational potential,temperature potential and matrix potential respectively affect the distribution of water content within the compacted loess,and the soil moisture measuring instrument for real-time monitoring of the moisture transfer process,found under the action of gravity water with the increase of height from the top showed "S" trend of increasing,and the dry density is small,the gravitational potential of 0 maximum moisture increased;Theeffects of temperature on the water transfer from the hot end to the cold end,the water content showed a "tangent" type progressive trend,cold end distance farther,the soil temperature is higher,the lower the water content,between temperature and moisture content by linear fitting;The soil water characteristic curve is measured by the pressure plate instrument,and the hyperbolic curve fitting of the soil water characteristic curve can get the function relation between the matrix potential and water content.Finally,based on the Harlan model equation of water movement and heat transfer of the transfer partial differential equations of coupled water and heat water,the empirical formula fitting function and other parameters into the model of moisture migration can be made of dry density and water content of these two variables included only in the model,the model can be used for simulation and calculation moisture migration.Study on basic properties of loess and water transfer law can guide the engineering practice,the test methods of soil water potential,a new sample preparation method and soil moisture measuring instrument can provide reference for future laboratory test.