Geoscience Reference
In-Depth Information
to place an airtight sheet on the ground surface. The injection can be performed by
using the surface soft soil layer as the sealing layer (Figure 7.45).
Kazemian (2011) has investigated the effect of this method on peat by using a new
binder (explained in Section 7.9.1) by injected the binder in soft soil after a constant
flow in the soil is achieved by the vacuum pipe. The results were compared with
conventional methods by pocket penetrometer after curing for 14 days. The unconfined
compressive strengths at pre-defined points at a depth of 100mm were measured by
pocket penetrometer and the changes are shown in Figures 7.46(a) and (b). Each tested
point was 20mm apart in a quadrilateral pattern. Figures 7.47(a) and (b) show the
affected areas in the samples respectively at a depth of 100mm.
It was observed that by applying a combination of injection and vacuum technol-
ogy in the samples, the affected area increased dramatically. The affected areas in the
samples were categorized in four groups (1) 0-100 kPa outer layer, (2) 100-200 kPa,
(3) 200-300 kPa and (4) 300-400 kPa center core.
Figure 7.47(a) shows that the horizontal extent of the affected area in sample I
(stabilized by conventional methods) is nearly 20 cm (15-35 cm along the
x
-axis), and
a small area of the sample had a strength of 300
400 kPa. On the other hand, by using
negative pressure by vacuum slots (sample II, Figure 7.47(b)), the horizontal extent of
the affected area was expanded to nearly 30 cm (10-40 cm along the
x
-axis), i.e. the
affected area increased from 20 to 30 cm. Furthermore, in this sample, more stabilized
areas with strength 300-400 kPa were observed.
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