Geology Reference
In-Depth Information
damage almost certainly was caused by long-period wave resonance
effects (Hencher & Acar, 1995).
The third verbal equation of Knill & Price (Knill, 2002) addresses the
interaction between the geological and environmental conditions at a
site and the construction and operational constraints and interactions.
The systematic review and investigation of site geology and environ-
mental factors, discussed in
Chapter 4,
needs to be conducted with
speci
how construction is to be
achieved and the long-term performance of the structure.
c reference to the project at hand
-
Drax Power Station, UK
It is often during construction that things go seriously wrong. An
example is provided from the 20,000 piles driven to support the
second phase of construction of Drax Power Station in Yorkshire,
UK. The ground conditions appeared to be straightforward with
about 17m of
3m of sand that
was typically dense and in turn overlying Triassic sandstone. This
pro
firm, varved silt and clay overlying 2
-
le was proved to be consistent across the site by numerous shell
and auger boreholes, with many SPT tests in the sand. Piles were
therefore expected to come to a halt during driving at depths of
about 18
19m. In the event, the piles were driven to depths which
varied unexpectedly and unpredictably by up to about 4m.
Figure 7.19
shows some of the piles; the holes in the front are where piles disap-
peared below carpet level without reaching a satisfactory resistance
(set) during driving. Where piles were driven to carpet level without
-
Figure 7.19
Driven
piles at Drax Power
Station completion.
Dark holes in
foreground are
where pile heads
have been driven
below carpet level
without achieving
an adequate set and
need re-driving.
