Pile Design and Construction Practice, Fifth edition

Resistance of piles to compressive loads 169

Ultimate base resistance of closed-end pile (MN)

Kulhawy/Vesic

N

q*N

g*values

Loose sand

2 × allowable load on

1 220 m OD×25 mm wall

thickness pile in high

yield steel

Dense sand

Depth of penetration (m)

0

0

5

10

15

20

25

30

5 101520253 0

es

alu

qv

vN

ntse

reza

Be

se

ul

av

q

N

ev

ts

an

ez

er

B

es

ul

va

g*

*N

q

N

sic

e

V/

y

aw

lh

Ku

Figure 4.14Base resistance versus penetration depth for 1220 mm diameter closed-end pile driven
into sand (a) loose sand (b) dense sand.

behaviour is similar with bored piles, when the loosened sand (which may initially be in a
dense state) slumps into the borehole. When piles are driven into medium-dense to dense
sands, radial displacement is restricted by the passive resistance of the surrounding soil
resulting in the development of a high interface friction between the pile and the sand.
Continued hard driving to overcome the build-up of frictional resistance may cause
degradation of angular soil particles with consequent reduction in their angle of shearing
resistance. In friable sands, such as the detritus of coral reefs, crushing of the particles
results in almost zero resistance to the penetration of open-end piles.
Driving a closed-end pile into sand displaces the soil surrounding the base radially. The
expansion of the soil mass reduces its in-situ pore-pressure, even to a negative state, again
increasing the shaft friction and greatly increasing the resistance to penetration of the pile.
Tests on instrumented driven piles have shown that the interface friction increases exponen-
tially with increasing depth as shown in Figure 4.15.