Soil porosity resulting from the assemblage of silt grains with a clay phase: New perspectives related to utilization of X-ray synchrotron computed microtomography

Abstract

Understanding the assemblage of basic grains is essential for predicting many soil properties. X-ray synchrotron microtomography with a high resolution was used for visualisation and quantification of the assemblage of silt grains with a clay phase containing 20% of clays. The 3D computed image was analysed after appropriate segmentation by using: (i) autocorrelation functions which enables anisotropy discussion of the assemblage; (ii) chord distribution which gives information on the size distribution of the void and solid phases; and (iii) the Hoshen-Kopelman algorithm (6-connectivity) in order to label each void with a unique number and thus enabling discussion of the connectivity. Our results show that X-ray synchrotron microtomography enables a more accurate analysis of the assemblage of silt grains with a clay phase than with conventional methods. Thus, it showed the isotropy of the silt-clay assemblage in the studied soil material. The void and solid phase volumes were smaller than 80 and 120 μm in all directions, respectively. The mean distance between two interfaces was 6.9 and 13.4 μm for the void and solid phase, respectively. X-ray synchrotron microtomography of the soil material studied also showed that the voids resulting from the assemblage of the silt grains with the clay phase can be considered as fully connected in the studied dried materials.