Sennebogen 6113 E sets barrette cages on Nice Haliotis 2 site

Earthquake protection for a €700m plant

Haliotis 2, between the Promenade des Anglais and the runways of Nice Côte d’Azur airport, is one of the largest water treatment projects currently under way in France, representing roughly €700 million including construction and operation. Before the treatment structures can be built, the existing dike has to be underpinned. On the seaward side, 82 stabilising barrettes are being installed along some 500 metres of dike to prevent slope failure in an earthquake. FAYAT Fondations holds the contract for this work.

Cages of 6.5 m width, 40 m deep

The barrettes are built using diaphragm wall technique. Each panel is excavated with a grab and desanded, then a purpose-made reinforcing steel cage is lowered in and the element concreted at depths of up to 40 metres. Individual elements measure roughly 6.5 to 6.6 metres wide with a wall thickness of 800 mm.

The lifting is handled by a Sennebogen 6113 E telescopic crawler crane supplied by SAML, a subcontractor of the FAYAT Group. Cages are picked up horizontally, brought upright and then threaded into the prepared excavation. Because the crane can travel with a suspended load and telescope under load, and offers full capacity through 360 degrees, cages can be walked into position in tight working space without the slew angle dictating what the crane can hold.

“On this site in particular, the simultaneous control of all movements is crucial. We can operate the undercarriage, upper structure, and boom movement at the same time without setting down the load. This makes positioning the reinforcement cages significantly easier.”

— Gilles Cortes, foreman and crane operator

Extraction loads on the boom

The 6113 E is not confined to cage work. It also installs and extracts casing and handles equipment during borehole desanding. Extraction in particular puts high dynamic loads into the machine and boom, which is where the crawler undercarriage and the boom’s structural design earn their place; the crane has to stay stable and precisely controllable through repeated cycles rather than single peak lifts.

For the contractor the appeal is a single machine covering cage handling, casing work and general site lifting on a confined coastal site, avoiding the outrigger set-ups and repositioning a wheeled crane would need between panels.

Source: Sennebogen — Photos: Sennebogen