Research On Particle-size Distribution And Soil-water Characteristic Of The Unsaturated Expansive Soil In Hefei District

The soil’s particle size composition affects its physical and mechanicalproperties, which plays an important role on the soil’s engineering characters.The soil-water characteristic is of great significance on predicting the strength,permeability and mechanical properties of unsaturated soils. As for theimportance of particle size composition and soil water characteristic,unsaturated expansive soils from9different construction sites in Hefei districtwere studied in this paper. The research on particle-size distribution(PSD) curveand soil-water characteristic curve(SWCC) was carried out.In terms of soil’s particle size characteristic, densimeter method and lasermethod were used to test the particle-size distribution curve. The test principle,measurement process and test results of these two methods were compared.Curve fitting was carried out for these two methods, through which therelatively complete fitting curves and fitting parameters were obtain. In addition,the compositions of tested soils were classified in order to obtain the basicparticle size composition information of expansive soils in Hefei district.With regard to the soil-water characteristic, the SWCCs were tested byosmotic method and filter paper method in this research. The testing methodswere introduced in detail, as well as the improvements. Based on the results ofosmotic method and filter paper method, relatively complete fitting curves andfitting parameters were obtained by using5fitting models. Furthermore, inorder to study the effect of tested soils’ volume change to their SWCCs, therelationship between void ratio and gravity water content was gained by steamhumidification test, and the SWCCs of unsaturated expansive soil consideringvolume change were obtained here.In addition, because of the consuming time and labors of SWCC tests, somepredictions were carried out based on basic properties of soil and PSD curve,which can provide convenient and fast methods to estimate the SWCCs ofunsaturated expansive soils in Hefei district.