Geoscience Reference
In-Depth Information
Figure 6.41
The soil stratigraphy at the Berengbengkel, Central Kalimantan, trial embankments (
after
Djajaputra and Shouman, 2003).
and carbon dating measurement identified that the age of the peat is approximately
4,000 years. The natural water content of the peat range from 467-1224%, with
organic content 41-99%, fibre content 6-56%, unit weight of 9-10.5 kNm
−
3
,pH
of 2-3, undrained shear strength 6-17 kPa, and coefficient of vertical permeability,
k
, of 3.5
10
−
8
ms
−
1
. Figure 6.41 shows the soil stratigraphy of the
trial site, Figure 6.42 shows cross-sections of the field trial and Figure 6.43 shows
the settlement performance of two of the trials: surcharge embankment and EPS
embankment.
From this trial, Rahadian
et al.
(2003) concluded that the surcharging method
works rather well, with settlement reaching a steady state condition after 200 days,
but the other four trials (i.e. normal embankment, timber and JHS (mini concrete), and
EPS embankment) were not successful. Both piled embankments (wooden and JHS
(mini concrete) piles), which are friction rather than end bearing piles, still showed
signs of settlement after 650 days, with total settlements of 1.2 m and 2 m respectively
(Figure 6.44). They attributed the possible cause of this to the very low friction between
peat and pile material (wood and concrete). The longer and heavier concrete pile JHS
system actually has more self weight than the shorter and lighter timber pile system.
The EPS embankment also showed a large settlement (about 1.6m).
However, Rahadian
et al
. (2003) admitted that direct comparison of the EPS
and pile embankments is not possible, as they have different geometries and rates of
construction. Furthermore, the embankments are built on different peat thicknesses.
In any case, they conclude that the surcharging technique is effective for a thin layer of
peat (less than 4m). Should piles be used, they should be driven to the hard stratum as
end bearing in order to minimize settlement, except of course for the transition zone.
10
−
7
-8.4
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