The city of Valencia on the east coast of Spain is no stranger to big races – it already hosts the prestigious America's Cup sailing event and the nearby Ricardo Tormo track is a regular car testing venue. But in August a new challenge rolls into town: Formula One’s Grand Prix of Europe.
Site workers have already started to create a harbour-side street circuit and now ground engineers are under pressure to reach the finishing line before the real race can begin.
The 5.47km racing grade track will include a section of new road through an old industrial site that will link the circuit at its south west corner.
A river runs along a 1km stretch of the new section and the ground comprises alluvial material typical to the area east of Valencia near to the sea. As the ground here is not strong enough to lay the road directly on top, a joint venture between Pennine and Geocisa is using top-feed, wet vibro stone columns to improve its bearing capacity.
The work is for client Generalitat Valenciana (the local government) by the main contractor – a joint venture between Fomento de Construcciones y Contratas, Pavasal and Becsa – and consultants Typsa and Ayesa.
"The approach to the job is, in a way, very simple," says Geocisa ground improvement manager Alejandro Segundo González. "We need to improve the characteristics of alluvial soil that lies beside the river for the new race track."
The €1M (£700,000) contract involves the installation of 10,000 columns at depths between 6m and 12m (although more typically they are between 7m and 11m). The ground profile comprises about 2m of fill that overlies about 4m of consolidated clay and then between 6m and 7m of sands and gravels.These columns are being installed by four rigs, each working 24 hours a day, seven days a week to complete the work in double-quick time.
Each of the four sets of equipment comprises a Pennine-manufactured HD 150 vibro flot mounted on a 70t or 80t Geocisa-built telescopic crane, each with Landini jetting pumps.
The 20m high cranes are too tall to work the entire area. This is because in three different places, low hanging power lines stretch across the site.
As a result, the main contractor decided to use band drains to improve the ground’s soil bearing capacity in these areas, installing them to depths of about 4m. The stone columns are installed at 2m centres directly beneath the track and 2.4m centres elsewhere.
In addition to the difficulties in manoeuvring around the site, a further constraint is an underground water pipe, which serves a nearby aquarium and runs below much of the length of the new road section.
To get round this, site workers are laying a new pipe beneath where the pavement will be.
"It makes it more difficult," says González. "We've already got a small area in which to work in one half of the site and we are not alone – in a 1km stretch there are maybe 15 activities going on at the same time."
On completing the ground improvement work, the main contractor will build the road, which will have two lanes in each direction and two new roundabouts.