Abstract: The aim of this research is to reveal the distribution characteristics of macropores in granite residual soil in three-dimensional scale.The characteristics of macropores of undisturbed granite residual soil in Fuzhou are characterized quantitatively as a case study by extracting the parameters of macropores via three-dimensional reconstruction using the representative volume element (RVE) based on CT (computer tomography)scanning images of the soil.Results unveil remarkable difference in the number of connected pores in granite residual soil samples but small difference in pore structure due to the similar causes of pore formation with the pore radius mostly between 1 mm and 4 mm.The topological spatial structure of pores in soil at different locations varies notably,with the coordination number of some pores reaching over 40,which is rarely influenced by depth.The coordination number of pores is mainly concentrated within 20,and the coordination number of pores above 20 is distributed in discrete points.Comparison among different processing methods demonstrate that the average pore diameter obtained by two-dimensional image processing is the smallest,and the porosity is quite different;the average pore diameter obtained by pore network model processing is the largest,and the pore distribution is relatively uniform;the difference of average pore volume between 3D reconstruction processing and pore network model processing is over five times.

Key words: undisturbed granite residual soil, CT scan, meso-structure, 3D reconstruction, macropores