A Microstructural Model for Soils and Granular Materials - Multiscale Geomechanics: From Soil to Engineering Projects - page 194

for the different nature of the constituents, as seen in the previous section. The
difference in nature between grains and aggregates is, however, insufficient to
explain the quantitative differences in the stress−strain relationship. In particular, the
deformability of the aggregates can play an important role in the relationship. This
deformability depends on the way in which the clay particles are assembled, which
is a function of the mineralogy, adsorbed ions, etc. The photographs in Figures 7.10
and 7.11 show two different examples of clayey materials:
- the kaolinite is made of small, rigid particles assembled in compact stacks;
- the bentonite is made of larger, more flexible particles creating less compact
and, therefore, forming more deformable aggregates.
Figure 7.10. Scanning electron microscope photo of kaolinite P300
Figure 7.11. Scanning electron microscope photo of bentonite
Analysis of the pore size distribution in the kaolinite by means of mercury
intrusion porosimetry confirmed the existence of two major groups of pore sizes:
one centered around 1 µm and the other around 10 nm. The first group corresponds
to the inter-cluster pores, whereas the second is related to the interparticle pores. The
number and size of the big pores progressively decreased when consolidation stress
increased, while the small pore size remained relatively unchanged under moderate