Abstract:
Piles can be classified into three categories depending on the amount of soil displaced
during installation: (i) Large volume displacement piles: (ii) Small volume displacement
piles and: (iii) Replacement piles. Installation of piles can disturb the soil surrounding the
pile and have an effect on the surrounding area by two different ways: (i) Due to variation
of the material properties of the soil surrounding the pile and: (ii) Due to changes in the
pore water pressure in the soil surrounding the pile. Magnitude of these variations is
highest in large volume displacement piles compared with small volume displacement
piles and replacement piles due to the high disturbance in the surrounding area caused by
large volume of soil displaced. Moreover. the pore pressure generated during installation
process might be dissipated with time depending on the permeability of the surrounding
soils and the structure of the soil disturbed due to driving may also be recovered with time.
The recovering of the soil structure with time and the equalization of pore pressure with
time is termed, "Tixotropic Recover". Time taken for the recovery to complete depends on
the amount of disturbance caused by the pile installation process and the properties of the
surrounding soil. Due to the strength regaining of the soil surrounding the pile as a result or
rixotropic recovery, the ultimate carrying capacity of the pile will vary with time. If the
ultimate carrying capacity of the pile is increased due to tixotropic recovery it is termed
'setup' whereas if it's decreased it is termed 'relaxation'.
