3.7 Reduction of negative skin friction >UV =k :Q
Provide dummy casing or sleeve around jG,^~ 5x
pile to prevent direct contact with ro^T L
settling soil 0fa8.g#I$
Predrill oversized hole through soft soil 92^Dn`g
prior to pile installation (hole filled with Fz] !2rt
bentonite slurry) ?9z1'6
Use of slender pile section in soft soil M:%Ll3
layers T>v`UN Bl]
Electro-osmosis B,A\/ %<
Current applied between pile (cathode) and i6k~j%0m
an anode causes migration of pore :Lq=)'d;6
pressure towards pile o H]FT{
Reduce effective stress and hence negative NOtwgZ-
skin friction oXGP6#
Very good effect on silty soils V&d?4i4/Q
Bitumen coating (see next slide) ,"T[#A~
If magnitude of negative skin friction is too large, the =CL h<&
pile may be coated with bitumen (above neutral e!4Kl:
plane) to reduce the negative skin friction (up to 90% 9YwS"~Q =w
reduction reported). 1tH#QZIT
=jvN8R*[
in practice, the bitumen coating methods have been widely used.
