Geoscience Reference
In-Depth Information
Figure 4.9
Vane shear strength profile of subsoil for site in Putrajaya, Malaysia.
than hemic (H4-H6) and sapric (H7-H10) peat. As noted by Edil (1997), the presence
of fibres affects the strength behaviour of peat.
Figure 4.9 shows the field vane shear subsoil profile of a new mosque project site
at Putrajaya, Malaysia. As shown, there is only a slight tendency for an increase in
strength with depth. The low bulk density of peat together with the high water table
implies low effective stresses with depth. Because of this there may not be a discernible
increase of strength with depth.
Yogeswaran (1995) reported the average field vane shear strength for tropical peat
found in Sarawak (East Malaysia) to be only 10 kPa, while the sensitivity ranged from 2
to 11. The higher water content and low dry density gives peat exceptionally low shear
strength. Because of this, and hence the low bearing capacity, a surface foundation on
peat has to be generally improved by fill materials before any engineering works can
commence. This will be discussed in detail in Chapter 6.
4.4 SHEAR STRENGTH INCREASEWITH CONSOLIDATION
In order to estimate and take into account the rate of increase of undrained shear
strength as a function of consolidation and subsequent densification of peat, Magnan
(1994) suggests that laboratory compression tests are performed, and the coefficient
λ
cu
=
c
u
/
σ
is then applied to the shear strength obtained from the vane test.
