Recent advances in the geotechnics of organic soils and peat - Geotechnics of Organic Soils and Peat - page 178

soil due to the electrical potential of the diffuse double layer and the space of the bulk
phase. In peat, the bulk phase due to the presence of fibres in fibric peat is higher than
in amorphous peat (Huat, 2004). Therefore the electroosmotic behaviour of peat is
under control of its structure. On the other hand, the structure of a peat is related to its
degree of humification. Therefore the electroosmotic behaviour of a peat is expected
to be influenced by the degree of humification (Asadi et al ., 2009f; Asadi 2010).
In tropical regions, the cations may be removed from the topsoil due to heavy
rainfall (Huat et al ., 2006). On the other hand, in coastal areas, because of the sea
water, the presence of cations could be different, and as a result, there might be different
behaviour of electroosmotic flow with depth and area (Asadi et al. , 2009f; Asadi 2010;
2011b).
Peats have noticeable qualities that make a suitable environment for utilization
of electrokinetic techniques, i.e. (1) the saturated mass is a good environment, (2) the
high charge and high specific surface area of the humus increase the presence of cations
for water momentum in electroosmotic phenomena, (3) the surface charge can cause
electroosmosis to occur (Asadi, 2010), (4) the decomposition processes affect the elec-
troosmotic behaviour, and (5) the resistivity can affect the electroosmotic behaviour
(Asadi et al . 2009c; Asadi et al, 2011f).
Asadi et al . (2011c) have done comprehensive investigations of the electroosmotic
behaviour of organic and peaty soils using electroosmotic cells (Figure 7.6). The cumu-
lative outflow volume profile over the testing period showed a continuous flow from
anode to cathode. The cumulative outflow volume of H3, H5 and H7 peat over the
10-day periods of the experiments were 97, 279 and 450mL, respectively. The rates
of flow were observed to diminish with time (Figure 7.7). The cumulative outflow
volume of H7 was higher than those of H3 and H5, meaning the cumulative outflow
volume of humified peat is higher than that of unhumified peat (Asadi et al ., 2011c).
The average coefficients of electroosmotic permeability ( k e ) of the H3, H5 and H7
peats were 4.91

10 − 5 cm 2 V − 1 s − 1 respectively. k e is
an indicator of the hydraulic velocity under unit electrical gradient. The maximum k e
of the H3 peat was less than that of H5 and H7. The k e of the peats increased after 2 to

10 − 6 , 1.12 10 − 5 and 1.57 × × ×

Figure 7.6 Electroosmosis apparatus ( after Asadi et al ., 2011c).