Describing the geometrical packing of gravelly cobble deposits using pair-correlation functions

Abstract

There is a close correlation between the mechanical behavior of gravelly cobbles and their geometrical fabric. In geotechnical engineering, the particle-size distribution curve is used to describe the particle gradation. However, a group of particles with the same particle-size distribution can result in several packing arrangements due to the different sedimentation processes. The particle-size distribution curve does not distinguish this characteristic. This study attempts to employ the pair-correlation function of point field theory for describing the geometric packing of gravelly cobble deposits. In the point field, a single gravel- or cobble-sized particle is represented by a point of its geometric center. The pair-correlation function can statistically illustrate the characteristics of a geometrical point pattern and is helpful in interpreting the neighborhood relationship between particles, such as the frequency of interpoint distances and the dominant particle sizes in a point process. Some examples based on ideal particle shapes and arrangements are analyzed to illustrate the interpretations from the pair-correlation functions. The characteristics of pair-correlation functions of field examples are also explained. It is shown that the pair-correlation function can provide another approach to understanding the geometrical packing characteristics of a gravelly cobble formation.Key words: gravelly cobble deposit, geometrical packing, interpoint distance, particle-size distribution, pair-correlation function, point field theory.