Experimental Study On Soil Water Characteristic Curve Of Loessial Silt In Full Suction Range

Loessial silt,as a kind of atypical loess,is usually not used in engineering construction in the past due to its special properties.With the rapid development of China’s economy and the rapid progress of modernization,in recent years,loessial silt has been more distributed in Shanxi in denser areas,the use of loess-like silt as a roadbed or foundation filler for engineering construction has gradually become the norm,and many problems in engineering are related to the unsaturated characteristics of soil,such as roadbed settlement caused by rainfall.In order to prevent and solve such related engineering problems and technical problems,it is necessary to deeply study the unsaturated properties of loessial silt.Therefore,this article through laboratory experiments,based on the basic theories and research methods of unsaturated soil mechanics,to study the unsaturated characteristics of compacted loessial silt has important engineering significance.Based on the above reasons,this paper is based on the loess-like silt of a construction site in Xinzhou,Shanxi,combined with pressure plate method,filter paper method and saturated salt solution method to measure the matrix suction.The main research content is to measure the soil-water characteristic curve of compacted loessial silt,analyze the influence of different initial dry density,initial water content and compaction energy on the corresponding soil-water characteristic curve;study the hysteresis of samples under different conditions in the high suction range;use classical mathematical models to fit And evaluate,select the model with the best correlation to analyze the relationship between the sample and the model parameters under different conditions.The results of this study are as follows:(1)The pressure plate method,filter paper method and saturated salt solution method are combined to obtain the matrix suction of compacted loessial silt.The results show that these three methods can be combined to effectively obtain the soil-water characteristic curve of the full suction range.(2)Soil samples prepared with different dry densities,water content and compaction energy have basically the same characteristics of soil-water characteristic curves,but when the matrix suction is between 100 k Pa and 200 MPa,under the same volumetric water content,the matrix suction of each soil sample is different.equal.It shows that as the dry density increases,the compaction energy increases,and the matrix suction of the soil sample increases;with the increase of the initial moisture content,the matrix suction of the soil sample increases.When the matrix suction is greater than 200 MPa,the soil-water characteristic curves of all soil samples coincide,and the soil-water characteristic curves are only related to the properties of the solid particles composed of the soil samples.(3)Both the Vang Genuchten model and the Fredlund&Xing2 model are mathematical equations suitable for fitting the soil-water characteristic curve of the full suction range of loess-like silt.Fitting with the Vang Genuchten model shows that the inlet air value and residual water content increase linearly with the increase of dry density.The Fredlund&Xing2 model fit shows that for samples with different initial water content,the air intake value is larger in the soil sample wet test,and the residual matrix suction increases with the increase of the initial water content.(4)Tthe hysteresis characteristics of the soil samples were studied by the saturated salt solution method,and it was found that the hysteresis effect of the soil samples under the heavy compaction energy was more obvious than that of the light compaction energy,but when the suction force was greater than 200 MPa,the hysteresis of the soil samples gradually disappeared.