Pile Design and Construction Practice, Fifth edition

42 Types of pile
Depth below sea bed (m)
5
10
15
20
25
TP3 –
TP4 –
Driving resistance (blows/200 mm)
0 50
100 150 200
TP3
First re-drive
1067 mm OD × 32 mm wall thickness
(50 mm at shoe) open-end steel
tube
1067 mm OD as TP3 but with
6 no. 0.451 × 0.303 × 7.0 m long
T-sections welded to outer
periphery at toe
TP4
Second re-drive
39 blows/200 mm
160 blows/200 mm
194 blows/200 mm
Piles driven by Menck MRB 1000 single – acting hammer (10 tonne ram, 1.25 m drop)
Sea bed
Loose very silty
fine sand
(N 5 2 to 11)
The pile was then cleaned out and plugged with concrete but failed under a test load of
6300 kN.
It was evident from the driving records that the plain piles showed little evidence of
developing base resistance by plugging and would have had to be driven much deeper
to obtain the required bearing capacity. In order to save the cost and time of welding-on
additional lengths of pile it was decided to provide end enlargements in the form of six
0.451 � 0.303 � 7.0 m long T-sections welded to the outer periphery in the pattern
shown in Figure 2.19b. The marked increase in driving resistance of the trial pile
is shown in Figure 2.20. The final resistance was approaching refusal at 194
blows/200 mm at 19 m below sea bed. The winged pile did not fail under the test load
of 6300 kN.
A disadvantage of the H-pile is a tendency to bend about its weak axis during driving. The
curvature may be sharp enough to cause failure of the pile in bending. Bjerrum (2.9) recommended
that any H-pile having a radius of curvature of less than 366 m after driving should
6.5
Dense slightly silty
fine sand with
gravel and cobbles
(N 5 50)
22.6
N denotes standard
penetration resistance
in blows/300 mm
Figure 2.20 Comparison of driving resistance of open-end plain and winged tubular steel piles at
Britoil Tanker Terminal, Cromarty Firth.