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Leigh Woods Abutment
The 26 metre high masonry tower on the Leigh Woods side of the Avon
Gorge stands on a red sandstone clad abutment which is 33 metres (110 ft) high. No original plans are
known to exist showing the design of the abutment, which was completed in1840. It was always believed
that the abutment was solid, a theory that was reinforced by a borehole investigation in 1969 which by
chance happened to go through a solid part of the structure.
However in 2002 it was discovered that the abutment comprises a honeycomb of 12 vaulted chambers in two
tiers, linked by narrow shafts and tunnels. The biggest chambers, which have a floor area of 17.25
metres (57 ft) x 5.6 metres (18 ft), are 10.8 metres (35 ft) high (almost the height of three
double-decker buses). The upper tier comprises seven chambers linked to each other, and to five more
chambers on the lower tier, by narrow tunnels and shafts only 0.6 metres (2 ft) in diameter. The lower
tier is built directly on to the rock of the Avon Gorge.
Checks by engineers have confirmed that the structure is safe. Although the chambers were not
ventilated, the air inside them was clean. There are no bats or other creatures not even spiders, but
stalactites up to 5 metres long hang inside some of them. Originally the chambers were accessible only
by abseiling specialists with caving experience, but easier access for maintenance purposes through the
side of the abutment has now been created.
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The saddles
When weight is placed on the Bridge the chains sag slightly. To accommodate this movement
and that caused by expansion in higher temperatures without placing extra load on the piers each pier
has two saddles to which the chains are bolted. These saddles are mounted on rollers so that movement
of the chains can be safely accommodated. Land saddles perform a similar function just below ground
level.
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The anchorages
The chains are anchored in tunnels in the rocks 17 metres (60 ft) below ground level at
the side of the gorge. The ends of the tunnels taper out so that the brick infill forms an immovable
plug. In 1925 the anchorages were strengthened with fixing stays and chains, and concrete.
The deck
The floor of the roadway was originally laid with seasoned Baltic Pine sleepers 125mm (5")
thick, overlain transversely with another floor of planking 50mm (2") thick. Until 1897 traffic passed
over the exposed wood but in that year the deck was covered with Limmer Dock asphalt. In 1958/9 all
timber was renewed.
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