Case study: seawalls

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Benefil fills the erosion voids behind the seawall at Pulpit Point on Sydney Harbour.

The problem confronting Sydney’s Hunters Hill Council engineers was how best to grout behind the sandstone seawall at Pulpit Point to compensate for the erosion by harbour tidal action. The section to be grouted was 40 metres long by approximately 4 metres wide, and of varying depth with a total volume of voids of about 40 cubic metres.

Council Chief Engineer, Don Cottie, decided to use a product originally developed for specifically this purpose in Holland, where there are many kilometres of harbour and canal walls, subject to much erosion from the big volumes of marine traffic. The product was Benefi, which offered many advantages over conventional solutions. One great advantage was in regard to site access. The Benefil® was taken to the site in a small truck. It and can be mixed on-site and pumped easily up to 150 metres from the truck and up to a further 50 metres from a single injection point, if required.

Incidentally, Benefil® is now widely used all over Northern Europe not only for seawall and retaining wall back-fill but also for filling all manner of underground voids including fuel, paint and chemical tanks that are to be ‘abandoned’.