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Ground investigations for four bridges on the volcanic island of Bioko, Equatorial Guinea, went back to basics in difficult conditions earlier this year.

UK contractor Emerson Moore Geosciences carried out the £45,000 job in West Africa for design and build contractor Fitzpatrick International. The scheme is part of a project for a ring road circling the country's capital, Malabo.

Two of the bridges are parallel concrete arch structures with single spans in excess of 100m that cross a 30m deep gorge.

Emerson Moore Geosciences director Jeremy Moore explained there were fault lines running under each abutment. He said problems with poor quality local drilling contractors were overcome by combining core data with Menard Pressuremeter testing and mapping to produce a conceptual ground model of the site, allowing an effective detailed investigation to be designed.

Moore added: 'Most of the really useful information was from geological mapping.' The company used extensive mapping and hand pitting down to depths of 5m to delineate strata boundaries in complex faulted sequences of basalts lava flows and pyroclastic rocks.

The estimated £80,000 second phase of the investigation is due to begin later this year.

May Gurney was winding up a six-week, £350,000 contract in Barking, east London as GE went to press. The firm installed 132 CFA mini piles inside the 57m by 34m footprint of the old town library.

Developer Wates is converting the 1960s structure into two six-storey apartment blocks.

The 300mm diameter, 11-16m long piles were installed at 1.2m centres using a 'hitmiss' sequence to ensure that boring did not disturb newly cast pies. Ground is 3.5m of fill underlain by 3.5m of sands/gravels and London Clay. The firm's two Hutte rigs were just able to operate in the space between the building's reinforced concrete ground and first fl oor slabs.

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