3.7 Reduction of negative skin friction *]/iL#
Provide dummy casing or sleeve around IkmEctAU
pile to prevent direct contact with k)z>9z%D
settling soil {tOf0W|
Predrill oversized hole through soft soil q%M~gp1
prior to pile installation (hole filled with vx7=I\1
bentonite slurry) Kt qOA[6
Use of slender pile section in soft soil 6n]jx:CZ,
layers 22ySMtxn
Electro-osmosis L9^M?.a
Current applied between pile (cathode) and /
j "}e_Q
an anode causes migration of pore @x*xgf
pressure towards pile e[Vk+Te7
Reduce effective stress and hence negative
{d#sZT
skin friction #?\(l%
Very good effect on silty soils =mX26l`B
Bitumen coating (see next slide) sk07|9nU
If magnitude of negative skin friction is too large, the ]jI<Js*F
pile may be coated with bitumen (above neutral og8hc~:ro
plane) to reduce the negative skin friction (up to 90% J9;fqQCt
reduction reported). g/68&
M
Is6}VLbB
in practice, the bitumen coating methods have been widely used.