Soil-Water Characteristic Curves and Permeability of Shanghai Soft Soils

Soil-water characteristics curve (SWCC) is a fundamental constitutive relation for the explanation of the engineering behavior of unsaturated soil. The study of SWCC is helpful for reducing the time and cost of unsaturated soil testing for engineering purposes. Some properties of unsaturated soils, such as shear strength and permeability, can be predicted from it. After a brief introduction to osmotic technique and vapour phase method, the SWCCs of Shanghai soft soil have been obtained and some basic characteristics of the SWCCs have been analyzed. Coefficient of permeability is an important parameter for unsaturated soils, but the wide range in coefficient of permeability has been proven to be a major obstacle in analyzing seepage problems. Childs and Collis-George proposed a model for predicting the coefficient of permeability based on the random variation of pore size. It was improved several times and proved to be effective. Based on this model, the relative coefficients of permeability of Shanghai soft soil are predicted from the soil-water characteristic curves. Results show that unsaturated permeability of Shanghai soft soil changes nonlinearly with suction.