| Soil-Water Characteristic Curve(short for SWCC) is an effective tool for describing the influence of unsaturated state on the hydraulic & mechanical behavior in unsaturated soil mechanics; the pore size distribution characteristic, as well as the water retention capacity of a soil sample, can be estimated through the position and shape of a SWCC in the 'water content-suction' space; in unsaturated soil mechanics, many research fields, such as the strength theory, seepage theory, consolidation theory and constitutive theory, use SWCC to reflect the influence of water content on the mechanical and hydraulic behavior of soil; Measruing SWCC is costly and time consuming, and the way of how to analyze and interpret the experimental data are far more difficult than that in saturated soil mechanics, which may become one of the reasons that prevent the unsaturated soil mechanics theory to be implemented in the engineering practice, to solve this problem, the following research work on SWCC has been carried out in this dissertation.(1) SWCC is usually used for estimating the parameters needed in the numerical calculation in unsaturated soil mechanics, by analyzing the characteristic of the existing SWCC models as well as the shape of SWCC, the aspects that need to be taken into account when determining the related parameters by using measured SWCC data have been discussed, after that, on the basis of the statistical results of 21 kinds of soils, a method that is able to estimate the parameters needed in the numerical calculation in the case that the measured SWCC data has not reached the residual state, has been proposed in this dissertation, with the help of this method, the use of SWCC in the engineering practice can become more convenient to some extent.(2) Based on the theory of probability, together with the relationship between SWCC and the pore water distribution function, a variable called the average pore size radius, which can characterize the pore size of a soil sample, is defined in this paper, and on the basis of this concept, a method for modeling the variation law of SWCC with soil deformation is then proposed. in this method, two measured SWCCs with known porosity is needed for calibrating the parameters, besides, the influence of the initial structure of a soil sample on the variation law of SWCC with deformation could also be taken into account in this method. (3) Based on the theory of probability, a saturated permeability function, which could take the influence of soil structure into account, has been proposed in this paper; combined with the Mualem(1976) relative permeability function model, together with the variation law of the structural parameters during deformation proposed in this dissertation, the influence of deformation on unsaturated permeability function was modeled, which can ensure the calculation results become more close to the practical situation.(4) Taking the fundamental theory of traditional domain model as the starting point, a simple model, which is able to simulate the hysteretic characteristic of a SWCC under arbitary drying and wetting paths, as well as predict the scanning curves in the case when the water content(or suction) variation history is unknown, is proposed in this dissertation; then, based on the proposed model, a method that is capable to predict the boundary wetting curve with the help of a measured boundary drying curve together with a first-order wetting scanning curve is presented, by using this method, the amount of the experiment data nessceary for calibrating the parameters in the hysteresis models could be reduced, which can make the hysteresis models more conveniently used in the engineering practice.
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