|
| The Foundations. |
|
This suspension bridge has the north tower
sited on the high water line and the south tower founded in shallow
water 500 metres from the shore. On the north bank at Hessle the side
span is 280 metres long with the anchorage on higher ground just north
of the Hull - Doncaster railway line. The southern side span, 300
metres west of Barton Haven, is 530 metres long with the anchorage
about 30 metres inshore.
On the north bank, a hard well-jointed bed of chalk comes near to
the surface and is covered by a tough layer of glacially deposited
chalky boulder clay. The anchorage and tower has taken advantage of
the chalk for good foundations and also the boulder clay has been
used to the best advantage as the basis for the approach road embankment
and the toll plaza area.
The areas on the south side where both the tower and anchorage are
situated, soft alluvium
is underlain by beds of boulder clay, sand and gravel. At 30 metres
depth, below these beds there is a deep bed of stiff, heavily fissured
kimmeridge
clay on which the tower and anchorage have been founded. |
|
|
| The Anchorage. |
|
 The
anchorages are massive concrete structures each having two chambers
in which the main cables splay out into separate strands. At the splay
position, the cables are supported by steel saddles mounted on top
of reinforced concrete pillars. The ends of the main cable strands
are attached to steel cross-head slabs at the face of anchor blocks
by strand shoes and anchor bolts. The crosshead slabs are pre-stressed
against the face of the anchor block by high tensile bars anchored
at the rear. The anchorages also support the ends of the side spans.
Hessle Anchorage is situated on the line of the bridge about 280 metres
north of the high water mark. It is 65.5 metres long x 39 metres wide
and founded in the hard chalk at a depth of 21 metres below ground
level. Barton Anchorage is sited 30 metres behind the river flood
Bund
above ground, it is similar to Hessle anchorage but the foundation
is cellular,72 metres long by about 40 metres wide filled with sand
and water and constructed within a framework of diaphragm walls which
reach 35 metres below ground level into Kimmeridge
clay. This anchorage has been designed to give an approximately
uniform bearing pressure under all conditions of cable pull. Certain
parts above ground level - the mass concrete infill, the architectura
ribs on the anchorage and the deck slab - were not therefore cast
until cable spinning was complete. Subsequently the mass concrete
infill was added while the box sections for the deck were being erected. |
|
|
| Tower Foundations (Piers) |
|
| The piers are reinforced concrete structures
which support the towers. Hessle Pier is situated on the high water
mark. It is a reinforced concrete structure 44 metres wide x 16 metres
long x 11.5 metres high and founded in hard chalk at a depth of about
8 metres below the ground level. Barton Pier is located in the river
about 500 metres from the south bank. It comprises a reinforced concrete
structure 16 metres thick supported on twin hollow circular cassions
each about 24 metres in diameter sunk by underwater excavation and
founded in Kimmeridge Clay about 36 metres below river bed level.
Although heavily ballasted during construction, the caissons have
been left empty in the final condition. |
|
|
|
| Page 2 for more Information |
|
|
|
