Pile Design and Construction Practice, Fifth edition

Ground investigations, contracts and testing 523

Where piles are installed through fill or soft clay these materials give positive support in
shaft friction to the test pile, whereas they may add to the working load in negative shaft
friction on the permanent piles. It may therefore be desirable to sleeve the pile through these
layers by using a double sleeve arrangement. Alternatively, the outer casing can be with-
drawn, after filling the annular space between it and the steel tube encasing the test pile with
a bentonite slurry.
It is inadvisable to test raking piles by a reaction from kentledge or tension piles since the
horizontal component of the jacking force cannot be satisfactorily restrained by the jacking
system. Cable anchors inclined in the same direction as the raking piles can be used but it
is preferable to determine the ultimate or allowable loads on raking piles by installing
special vertical piles for loading tests.

Yoke Universal beams

Bracing

'Load cell

Hydraulic jack

Test pile

3 B

(not less than 2.0 m)

B

Cap cast

on to head

of test pile

Anchor piles

Four dial gauges

Dial gauge

supports

Tension

members

Figure 11.8Testing rig for compressive test on pile using tension piles for reaction.

Saddles

Four dial

gauges

Universal beams

Load cell

Dial gauge supports Hydraulic jack

Cap cast on

to head of

test pile

Test pile

B

3 B

(not less than 2 m)

Cable anchors

Figure 11.9Testing rig for compressive test on pile using cable anchors for reaction.