Development and Evaluation of a Numerical Model being able to Simulate Soil Pore Size Change

The aim of the thesis is to develop a numerical model based on first principles for the simulation of change of size of soil pores during drying of soft soil. This model is suitable for the type of soil consisting of clay with layered structure, such as Montmorillonite. In this study, the geometry of the soil pore is idealized by a triangle consisting of three sand grains and clay fabrics connecting the sand grains. The simplified structure is named as unit cell in this thesis. The change of size of soil pore results from deformation of clay fabrics, and the clay fabric deforms due to the variation of water content. The length of clay fabric is related to the chemical potential of water by applying the Diffuse Double Layer theory as well as geometrical considerations. The soil mass is modelled by combining unit cells of different original pore sizes, which is randomly generated. The model is built by Matlab. The inputs include soil properties (porosity, clay fraction, lamellar properties, etc) and distribution factors; the outputs are total volume of soil and volume of wate, further derivation gives the Water Retention Curve and Soil Shrinkage Curve. In conclusion, the model is able to provide reasonable prediction of change of soil pore size. The shrinkage of pore due to drying of soil is observed. It is found that the multiple unit cells model provides more reasonable results compared with the single unit cell model. This is a preliminary study, the author recommends to validate the model by experiment; in addition, more comprehensive multi-dimensional parameter analysis is needed.