|
|
Contrary to
most of pile design, the design of min-piles is controlled by internal
capacity instead of external carrying capacity due to their small
cross-sectional area.
|
There are
mainly two reasons for designing mini-piles as friction piles:
(i) Due to its high slenderness ratio, a
pile of 200mm diameter with 5m long has a shaft area of
100 times greater
than cross-sectional area.
Therefore, the shaft
friction mobilized should be greater than end resistance.
(ii) Settlements of 10%-20% of pile diameter
are necessary to mobilize full end bearing capacity, compared
with 0.5%-1% of
pile diameter to
develop maximum shaft resistance.
Left-in casings
for mini-piles have the following advantages:
(i) Improve resistance to corrosion of main bars;
(ii) Provide additional restraint against
lateral buckling;
(iii) Improve the grout quality by preventing
intrusion of groundwater during concreting;
(iv) Prevent occurrence of necking during lifting
up of casings during concreting.
*
* * * *
