Orientation of aggregates of fine-grained soil: quantification and application

Abstract

The orientation of aggregates in fine-grained soil is an important factor that influences the anisotropy and the engineering property of the fine-grained soil. This paper reviews the basic principle and functions of the computer image processing system for soil fabric, and proposes two new quantitative indices to assess the orientation of aggregates of fine-grained soil, which include alignment entropy (Hm) and frequency distribution function of clay aggregate orientation Q(α). The significance of Hm and its differences with anisotropy index (Ia) are discussed. Q(α) enables the orientation of the aggregates to be continuously represented from 0 to 180° and is also taken as a quantitative parameter reflecting the anisotropy of the fine-grained soil in the microstructural mechanical model. The latter sections in this paper give two examples showing the applications of these indices. The first example appraises the changes of fabrics of fine-grained soil during the process of compacting. The examination results confirm the phenomenon that the deformation of the soil samples during the process of compacting is mainly due to the re-alignment and deformation of clay aggregates rather than clay platelets; the other example represents the application of the Q(α) in fitting the creep of anisotropic fine-grained soil by the micromechanics model. The fitting results indicate that it is proper to take f(n)=Q(α).