The owner of the site, Haventus, is redeveloping the 450-acre Ardersier Port as an energy transition facility to serve offshore wind farms and other energy projects.
Ardersier, a former North Sea oil and gas fabrication yard, closed in 2001.
O’Keefe has carried out extensive cement stabilisation works to create a 1.5km-long haul road ready for the main construction works.
Using a German-built Wirtgen WR250 soil stabiliser, O’Keefe has mixed approximately 1,500 tonnes of cement into the sandy soil and spread a 150mm layer of crushed concrete over the top. The cemented crush concrete offers a more robust layer as stabilised material is not a wearing course.
Soil stabilisation, using either lime or cement, is a well-proven method of transforming unstable cohesive soils into a stiff granular texture capable of bearing dynamic and static loads.
Brian Doogue, O’Keefe’s soil contracts manager, explained: “Cement stabilisation allows us to use site-won material rather than bring in thousands of tonnes of expensive aggregate. It’s cheaper and more environmentally-friendly.
“We built the haul road to a precise design, with a camber in the middle to shed water. The road consists of cement-stabilised soil to a depth of 300mm with a layer of crushed concrete bringing the total depth to 450mm.”
Preparatory works began last year with site visits and testing soil samples. O’Keefe’s soil engineering specialists then designed a mix to suit the site conditions.
“There is no water supply on site, but we’re right by the sea, so we designed a recipe that can cope with the salt in the water,” said Brian Doogue.
Work on the soil improvement began in late May and was completed in mid-July, two weeks ahead of schedule.
As well as the Wirtgen machine, O’Keefe used an articulated dump truck to carry materials and a Caterpillar D6 bulldozer with GPS machine control to profile and level the road surface. The finished surface was compacted with a 16-tonne single-drum vibrating roller.
“We finished early and everything is done, bar the plate load testing, which is happening now,” added Mr Doogue.
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