Pile Design and Construction Practice, Fifth edition

300

Piles driven into very weak

to weak coral detrital limestone

(N-value increasing from 20 blows

to 60 blows per 300 mm over

depth from 4 to 35 m below

ground level). 762 mm OD

tubular steel piles driven

with closed ends by diesel

hammer (rated energy 13 500 m/kg

per blow)

200

Driving resistance (blows/0.5 m)

100

0

5

10

15

Depth below ground level (m)

20

25

30

35

Figure 4.31Low resistance to driving of tubular steel piles provided by weak coral limestone.

Table 4.15CIRIA recommendations for the shaft resistance of displacement piles driven into chalk

Chalk classification Type of pile Ultimate unit shaft
resistance (kN/m^2 )

Low to medium density, open joints Small displacement 20
Small displacement,H-sections 10
Large displacement, preformed 30
High density, closed joints Small displacement, open end 120
tubular
Large displacement, preformed (100) verify by load
in pre-drilled holes testing