Pile Design and Construction Practice, Fifth edition

254 Pile groups under compressive loading

Figure 5.16Relationship between Eu/curatio for clays with plasticity index and degree of

over-consolidation (after Jamiolkowski et al.(5.9)).

1600

1400

1200

1000

800

600

400

200

0

123

PI<30

PI>50

30 <PI<50

Over-consolidation ratio

45678910

Eu

/cu

For stiff over-consolidated clays:

immediate settlement (5.15)

consolidation settlement (5.16)

final settlement (5.17)

For soft normally consolidated clays:

immediate settlement 0.1 (5.18)

consolidation settlement (5.19)

final settlement (5.20)

The Eu/curatio is also strain dependent showing a reduction in the ratio with increasing
strain. Jardine et al.(5.9)showed this effect in London Clay from the results of undrained
triaxial tests on good quality samples (Figure 5.17). Normally loaded foundations, includ-
ing pile groups, usually exhibit a strain of 0.01% to 0.1%, which validates the frequently
used relationship Eu 400 cufor the deformation modulus of intact blue London Clay.

oed

oed

oed

oed

i 0.4 to 0.5oed

i 0.5 to 0.6oed