The Study On The Metric Suction Of Unsaturated Clayey Soils

Many deformation failure of soil belong to the deformation failure of unsaturated soil in nature and human engineering activities. since 1960s,the research emphasis of soil mechanics turn to the unsaturated soil, the study of engineering property and strength theory of unsaturated soil has developed to be the frontier topics of the subject geotechnical engineering. The metric suction is the key factor of unsaturated soil, and because of the influence of factors such as grain composition,mineral composition,pore structure,dense degree and stress history, the influence mechanism of unsaturated soil'metric suction is very complex.This study used laboratory experiment to test the six slip soil which selected from the typical landslide of three gorges area, and measure the metric suction of unsaturated soil which have the different grain composition and the different clay mineral composition. The negative exponential function relationship between metric suction and humidity can be seen from this sample soil testing, from which four characteristic parameters of soil-water characteristic curve of different types of unsaturated clayey soil have been derived, that is residual humidity, residual metric suction, the difference between saturated and residual water content and sensitivity of metric suction to water content. The relationship between these four characteristic parameters and the clay, silt, sand as well as gravel has been analyzed in view of both single correlation and partial correlation. It can be concluded that grain composition affects the four characteristic parameters mentioned above to different extent, of which residual humidity is influenced to much further degree. Based on partial correlation analysis, the four characteristic parameters have the best correlation with the content ratio of coarse grain and fine grain. Finally, three typical soil sample have are chosen. From the point of clay mineral components, the analysis of the effects that these three sample clay mineral contents have on the four characteristic parameters has been carried out.In this study, the selected sample soil is from slide zone, which is quite typical and improves the factor of unsaturated clayey metric suction.