 |
Client: Environment Agency (EA)
Project : River Witham flood defences
Using old car tyres as an economic, innovative fill material for strengthening an unstable riverbank earned May Gurney a nomination for the 2004 Fleming Awards
for excellence in Geotechnical Design & Construction.
The tyres were used to strengthen a section of the River Witham bank in Lincolnshire as part of the £10m River Witham Phase 2/3 Contract for the EA.
A 1600m length of embankment between the River Witham and Branston Island flood storage area needed to be widened and made stable. The traditional method
of clay fill was not practical due to the close proximity of an overhead power line and a soke dyke (drainage ditch) running parallel with the flood embankment.
The team used tyre bales because they offer lower driving forces due to their low unit weight and provide high internal friction, allowing the embankment to be
constructed with a steeper side slope. This minimised the embankment footprint area and reduced primary and secondary consolidation settlement.
An average of 100 tyres were strapped together to form rectangular bales, which were laid two deep in stepped benches cut into the landward side of
the embankment. A geotextile membrane, positioned around the bales, prevents soil from infilling holes between the tyres - ensuring the bundles remain
relatively light. All 10,000 bales are buried under a layer of backfill/topsoil to create a steep slope.
|
| |
