Geoscience Reference
In-Depth Information
Figure 5.26
Effect of pH on permeability (
after
Asadi
et al
., 2011a).
state, peat can have a hydraulic conductivity as high as sand, i.e., 10
−
3
to 10
−
2
cm s
−
1
.
Hydraulic conductivity decreases markedly under load, down to the level of silt or
clay hydraulic conductivity, i.e. 10
−
6
to 10
−
7
cm s
−
1
or even lower (Dhowian and Edil,
1980).
In general, horizontal hydraulic conductivity, especially for predominantly fibrous
peats, is greater than that in the vertical direction by an order of magnitude or more
(Dhowian and Edil, 1980).
5.3.1 Effect of pH on permeability
Asadi
et al.
(2011a) investigated the effect of pH on permeability of tropical peaty soils
under laboratory conditions. Initially the pH of the pore peat water was adjusted by
drop-wise addition of a 0.1M HCl or 0.1M NaOH solution. Then the undisturbed
sample in the mould was saturated under pore peat water pressure. The pore peat water
was allowed to flow through the specimen and the permeability value calculated. It
was found that in both amorphous and fibrous peats, the permeability increased as the
pH decreased (Figure 5.26). The alkaline conditions had contrary effects, i.e. as the
pH increased the permeability of both amorphous and fibrous decreased. The results
showed that effects of acids and bases on the permeability of the fibrous peat were
lower than those of amorphous peats (Asadi, 2010).
5.4 FINAL SETTLEMENT DUE TO SURFACE LOAD
A conventional one-dimensional formula may be used with the above compressibility
parameters to calculate the total settlement in peat. Alternatively, a simpler formula,
as proposed by den Haan and El Amir (1994), may also be used. According to them,
w
o
−
w
ε
=
(5.9)
w
o
+
0
.
371
+
0
.
362
N
