Three-dimensional characterization and simulation of anisotropic soil fabric

A procedure for constructing resin impregnated sand specimens for fabric (microstructure) analysis is presented. The impregnation device provides excellent control of the impregnation rate and confinement for different types of soils. Such control is necessary to minimize disturbance to the soil fabric during impregnation. The proposed technique also allows monitoring of the uniformity of impregnation throughout the process. Image analysis techniques are used to examine the variation of porosity at the microscopic and macroscopic levels within specimens. The analysis shows that about twice the deviation in local porosity from average porosity is obtained when microscopic measurements are used, as compared with the macroscopic measurements. Soil fabric anisotropy is characterized using two directional functions. Each of these functions has two components: an average value that describes the isotropic condition and a deviatoric tensor that represents the deviation from the average. They are shown to capture the relative distribution of air voids and their connectivity in different directions. The functions are also used to simulate the three-dimensional anisotropic fabric of soils in a computer.