Research On Suction Of Unsaturated Loess-bonded Water

The engineering characteristics of unsaturated loess are mainly affected by the change of suction in soil,which corresponds to the change of water content in loess.At present,there is still a lack of research on the occurrence of water in unsaturated loess,especially the content of water and its state.In this paper,the adsorbed bound water test of loess from Zhengning in Gansu province and Jingyang in Shaanxi Province is carried out,the bound water content and limit are determined.The thickness of the bound water film of loess is estimated based on the Halsey equation,the suction is classified according to the occurrence state of the water in the loess,and the soil-water characteristic curve of the water is obtained with the Kelvin equation.Firstly,the bound water content of Zhengning and Jingyang loess is determined by isothermal adsorption,which shows that the water content of the adsorbed bound water of Zhengning loess is concentrated in the 4%-9% range,the boundary humidity of the strong bound water and the weak bound water is RH=0.90,the boundary humidity of Jingyang loess is RH=0.59.The difference between the two is mainly caused by the difference in clay mineral content and particle size gradation.The structure of loess has little influence on the content of the adsorbed bound water,but certain influence on the adsorption process according to the isothermal adsorption results of undisturbed loess and dispersed soil samples in Jingyang.Based on the adsorption water test,the value of parameter C and s in the equation are obtained by the temperature adsorption curve fitted by the Halsey empirical equation.The results shows that different loess has the same value of the parameter s,which is 2.The parameter C is related to the content of colloidal particles in soil and the specific surface area and its correlation equation is obtained by fitting.According to the occurrence state of the water in the loess,the suction of the soil is divided into the adsorption action of the bound water and the capillary action of the capillary water.Combined the Kelvin equation,the soil-water characteristic curve of thewater is obtained.Then the residual water content of the loess is obtained by the soil-water characteristic curve.And the soil-water characteristic curves of the adsorption water are predicted by the empirical formula of water film thickness and the related physical parameters.