Civil Engineering Reference
In-Depth Information
Figure 7.3
Buckling of steel H-pile driven into boulder clay. (Photograph courtesy of Sir Robert
McAlpine & Sons Ltd.)
Table 7.1
Pile driving records for typical steel H-pile: Denton Island Bridge, Newhaven, Sussex
(Courtesy East Sussex County Council)
Date
Depth (m)
Driving resistance
(blows/0.25 m)
Comments
29.3.83
12.5-27.5
3-5
Hammer: 4 tonne drop weight, fall about 1 m
11.4.83
27.5-32.5
8-10
Soil profile: 0-30 m silty clay
11.4.83
32.5-36.0
12-15
alluvium
11.4.83
36.0-41.25
9-12
30 m—upper chalk SPTSs in top 6 m
11.4.83
41.25-47.0
15-18
of chalk gave
N
=
35 to 50
47.25
68
blows/300 mm, i.e.
47.5
59
Grade I material
47.75
63
Below 36 m no data
48.00
47
15.4.83
48.25
81
Design length of pile
48.5
78
pile 36 m
48.75
68
49.00
43
Pile completed
inadequate bearing capacity at the designed length, when tested 14 days after driv-
ing. The piles were lengthened by about 10m, and re-testing proved them to be
satisfactory.
In dense silts and some weathered rocks, the reverse effect may be observed. It is
postulated that negative pore-water pressure may be induced by pile driving, leading
