A specialist team from civil engineering contractor O’Keefe has completed extensive ground improvement works for a port development near Inverness.
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 and prior to the commencement of the current project, was the UK’s largest brownfield port.
O’Keefe has carried out extensive cement stabilisation works to create a new 1.5km-long haul road ready for the main construction works.
Using a highly-specialised 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, explains: “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,” adds Mr Doogue.
Preparatory works began last year with site visits and the testing of 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,” explains Mr Doogue.
Work on the soil improvement began in late May and was completed in mid-July, some two weeks ahead of schedule. Besides 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,” says Mr Doogue.
“O’Keefe has a strong track record in this type of work – we’ve been doing it for more than 20 years. This project demonstrates how our stabilisation and earthworks teams can deliver a nation-wide service,” he concludes.