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Monkey business


Van Elle has been piling at Colchester Zoo and Chessington Zoo, both for foundations, but for very different kinds of accommodation.

The job at Colchester comprises an enclosure to house two orangutans and make room for six more as well as for ring-tailed macaques and tropical butterflies. The building will be about 35m by 16m with 4m underground and feature a glasshouse on top.

It will include a public walkway from the sea lion pool, which is tunnelled below the main entrance road, where it will enter the orangutan enclosure and climb back up to ground level at the other side.

Project engineer Richard Jackson needed a piling solution for a retaining wall. It was initially thought that secant walling was required, but after investigation Van Elle's final design allowed for a contiguous method that provided a cost saving to the client and a reduction to the programme as the work was completed in one week.

Rig crews installed 98, 600mm CFA piles at 750mm centres through sands and gravels to a depth of 12m. The design also specified a maximum defl ction of 15mm, a requirement for the glasshouse.

Once excavated down to the 4m depth, a concrete wall will be built and then cladded with a rock-like facing stone.

The contractor's group managing director Richard Holmes is particularly looking forward to seeing the finished enclosure on the £100,000 scheme as he has adopted an orangutan in Borneo. It should be ready to receive its new inhabitants in early spring 2007.

At Chessington World of Adventures the company worked on a safari hotel for visitors who wish to spend several days at the park. Site workers installed more than 400, 200-250mm precast driven piles through firm to stiff clay overlying sand and gravels, to depths of 1112m. The site of the £87,000 job is in two main areas and was phased to allow diversion of the access road.

Work on the 525kN safe working load piles was expected to take three weeks to complete, using a Junttan precast piling rig. Van Elle says its operating process allows work to be carried out with only two operatives, with a pile being installed every 10 to 15 minutes.

Both projects were scheduled for completion last month so it will soon be a good night's sleep for the 'old men of the woods' (orang-utan in Malay) at Colchester and the residents of the safari hotel in the woods at Chessington.

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