Types of pile 41Because of their relatively small cross-sectional area, H-piles cannot develop a high
end-bearing resistance when terminated in soils or in weak or broken rocks. In Germany
and Russia it is frequently the practice to weld short H-sections on to the flanges of the
piles near their toes to form ‘winged piles’(Figure 2.19a). These provide an increased
cross-sectional area in end bearing without appreciably reducing their penetrating ability.
The bearing capacity of tubular piles can be increased by welding T-sections on to their
outer periphery when the increased capacity is provided by a combination of friction and
end bearing on the T-sections (Figure 2.19b). This method was used to reduce the penetration
depth of 1067 mm OD tubular steel piles used in the breasting dolphins of the Britoil
Marine Terminal in Cromarty Firth. A trial pile was driven with an open end through 6.5 m
of loose silty sand for a further 16 m into a dense silty sand with gravel and cobbles. The
pile was driven by a Menck MRB 1000 single acting hammer with a 1.25 m drop of the
10 tonne ram. It will be seen from Figure 2.20 that there was only a gradual increase in
driving resistance finishing with the low value of 39 blows/200 mm at 22.6 m penetration.
Tubular pile(a) (b)T-sections cut from
H-section pileFigure 2.19Increasing the bearing capacity of steel piles with welded-on wings (a) H-section wings
welded to H-section pile (b) T-section wings welded to tubular pile.