Historically, high quality farmland in this area has been protected
by clay embankments generally armoured with a layer of Essex Blocks
(115mm thick) jointed with hot-poured mastic. Essex Blocks perform very
well under moderate wave attack, where the embankment is stable, and
where the slope lengths are not too long.
Where blocks are loosened and
removed – in areas of settlement or relatively high wave attack –
failure is rapid and progressive.
With high annual maintenance costs for
the most exposed or unstable areas, our client, the (then) National
Rivers Authority sought a more cost-effective solution using Lean Stone
Asphalt (LSA)/Open Stone Asphalt (OSA).
Essex blocks stripped off the embankment and placed to protect the toe
150mm LSA placed as filter and regulating layer
150mm OSA armour placed in situ over LSA, following all shapes and contours