Geoscience Reference
In-Depth Information
Figure 7.35
(a) A cylindrical test specimen from the original soil sample after trimming; (b) method
used to set up the cement column in the specimen (
after
Kazemian
et al
., 2012b).
the samples was determined using a triaxial compression test under unconsolidated
undrained (UU) conditions to determine the shear strength of peat.
The procedure for setting up the specimen in the triaxial apparatus is shown in
Figure 7.35. The specimen's height and diameter were 100mm and 50mm respectively.
To prepare a peat sample reinforced with cement-sodium silicate and kaolinite in
order to investigate its undrained shear strength, a PVC tube was placed at the centre
of the peat specimen and used to remove a portion of peat from the cell. The removed
portion of peat was replaced with different ratios of ordinary Portland cement, calcium
chloride as reactor, sodium silicate (Kazemian
et al
., 2012b), water, cement, kaolinite
and peat. The cement column's diameter was 20mm.
Different compositions of chemical grouts (sodium silicate, calcium chloride,
cement and kaolinite) were considered. The samples were then cured for 28 days
in a soaking basin with natural peat water (collected from the peat site). A triaxial test
(UU) on each sample was subsequently carried out.
The effect of sodium silicate (0, 1, 2.5 and 5.0%) on shear strengthwas investigated
while other parameters remained constant (calcium chloride 2%, kaolinite 20% and
cement 15%). Based on the results in Figure 7.24, there was an increasing trend in
the shear strength with 1.0% and 2.5% sodium silicate compared to the conventional
binder (i.e. 0% sodium silicate). However, higher shear strength was achieved with
2.5% sodium silicate. This indicates that 2.5% sodium silicate was an effective dosage
to give a reasonable strength (Figure 7.36).
The mechanisms of peat soil stabilization under the effect of sodium silicate can
be explained by following reactions (in some conditions):
+
−−−−→
+
Cement
water
C-S-H gel
Ca(OH)
2
(7.8)
Na
2
(SO
3
)
+
Ca(OH)
2
−−−−→
Ca(SO
3
)
+
2Na(OH)
(7.9)
The effect of ordinary Portland cement (0, 40 and 50%) was investigated while
other parameters remained constant (Figure 7.37). From the results obtained (Figure
7.36), the strength increased as the percentage of cement increased. A 50% proportion
of cement gave the highest value, but the effective dosage is yet to be calculated since
the strength gain from 0-40% is better than from 40-50%. These findings agree well
with Kazemian
et al
. (2010a), Kalantari
et al
. (2010, 2011) and Duraisamy
et al
.
(2007a, 2009).
