Recent advances in the geotechnics of organic soils and peat - Geotechnics of Organic Soils and Peat - page 180

Figure 7.9 Variation of coefficient of electrooosmotic water transport efficiency with time ( after Asadi
et al ., 2011c).
The flow through a soil varies considerably depending on many factors, such as
the minerals present, particle size distribution, porosity, soil fabric and the nature
of the pore fluid. Despite the fact that H3 peat had less fine particles than those
of H5 and H7 peat, and was therefore, more permeable, the H3 peat had a lower
coefficient of electroosmotic permeability. A good understanding of humus as the
most chemically active fraction of the peat colloids could make clear the underlying
reasons for the significant differences. The humified peat had a more active fraction
than unhumified peat, resulting in a higher coefficient of electroosmotic permeability
(Asadi et al ., 2011e). The zeta potential measurements also proved that the surface
charge of the humified peat was higher than the surface charge of the unhumified peat
(see Chapter 3). The H7 peat had a larger surface area per unit mass (i.e. smaller
particles) and had a higher proportion of the sample passing the #100 sieve. Therefore
the quantity of the humus portion in H7 peat was higher than in H3 and H5 peat
(Asadi, 2010).
Since the humus is dynamic and very active in charge (Stevenson, 1994), the H7
peat had a higher electroosmotic conductivity. Therefore the very highly decomposed
peat had significant differences in electroosmotic properties compared with undecom-
posed peats. The study confirmed that the coefficients of electroosmotic permeability
of the peats were dependent on the CEC, specific surface area and the degree of peat
humification (Asadi et al ., 2011c).
7.3 ELECTROKINETIC CELL
Asadi (2010) proposed two types of setup for electrokinetic investigations on organic
and peaty soils. Figure 7.10 shows a schematic electroosmotic cell (Type I) which most