Heavy rain has provided contractors working on massive road building project in Spain with a slippery problem. Adrian Greeman reports.
OK it is a clichÚ, but last winter the rain in Spain really did fall mainly on the plain. Lots of it.
Around capital city Madrid, which sits right in the middle of the Spanish plain, the unusually bad weather heavily affected construction, especially earthmoving. For contractors working on the huge road building programme under way around Madrid, waterlogged ground conditions have caused significant slippage against programme.
'We may be obliged to accelerate our working later this summer to catch up, ' says Antonio Morollon, project manager for one of the largest schemes, the Radiales toll road system, and the associated outer motorway ring for the city.
Despite the blazing Spanish sunshine since early May he says the ground has retained water and loaders, excavators and trucks are still having problems with the waterlogging in places.
Cement stabilisation for the road base has also been slowed, though construction of roadside drainage early on safeguarded against greater delays.
Morollon's company FCC Construccion leads the Radiales consortium. This is working on two of the four 30km long 'spokes' which make up the new system and a quarter circle section about 40km long of the M50, which is an outer ring road for the city. FCC's 35% stake in the consortium is equalled by ACS Proyectos Obras y Construcciones, while OHL and Sacyr share the remainder.
The contractors are also part of the financing group which is delivering the roads, under a 50 year build and operate arrangement.
The total 100km of or so of motorway which falls under Morollon's management has involved a massive earthmoving operation totalling some 27M. m 3. It has been carried out by a subgroup of contractors led by major earthmoving firm Epsa and 10 other small companies.
The wide variety of plant, from Hitachi and Komatsu to Epsa's primarily Caterpillar machines and the ubiquitous Mercedes truck, testifies to the range of operators.
The plains have more shape to them than might be thought and there are some fairly large works on the project. They include one cutting reaching 40m deep and stretches of cut and cover tunnel - a double section is needed over 1.5km of the M50 where it passes through an environmentally sensitive area and another shorter length on one of the radial spokes, the R3.
Ground is mixed but primarily made up of layers of sand and silt, in some places with a higher proportion of gravel and in others with silts and sometimes clay. 'It is these finer elements of the matrix which tend to retain the moisture, ' says Morollon. He says one section of R3 is across chalk which created some further problems. 'It was hard enough in places to require blasting.'
Despite the rain he says the earthmoving is now 95% complete. 'And in fact the earthmoving has not been our major difficulty, ' he says. 'We have had far more problems with the junctions and interchanges.
'They are not difficult technically in construction terms, although some are quite extensive. But we have a high traffic density and some require complex road diversions.'
The new radial roads will eventually interchange with both the new M50 and existing ring roads. Traffic on these has to be kept running at all times.
Diversion works in places are almost as robust as permanent work to achieve a free flow.
The contractors' group itself does the analysis and design And as a ring road, the M50 cuts across and must interchange with numerous existing 'spokes' into the city.
'Altogether there are about 170 structures, ' says Morollon.
Interchanges and slip roads caused bigger problems early on too. An original schedule for the road slipped back by nearly two years because of disputes and procedural and planning problems over many of the interchanges. 'The problem is that there are various authorities concerned with the project, with sometimes differing views, ' says Morollon.
Most of the interchanges are constructed in concrete, using precast I beams for the spans, although in one or two places insitu concrete has been poured for curved spans. There are no dramatically large bridges.
Attention at present is on the road formation. The project is possibly one of the largest in Europe to use stabilisation techniques, with most of the dual three lane M50 and the dual two lane R5 built up on a cement stabilised foundation.
First comes a 300mm deep layer of insitu stabilisation, using a 3% cement addition, mixed in by four big Wirtgen stabilisers, capable of handling up to 10,000m 2per day each. Formation levels are controlled with an extensive use of automatic controls fitted on the bulldozers and scrapers. 'It helps deal accurately with the large amount of work to be done, ' says Morollon.
On top goes a 300mm-350mm thick layer of plant-mixed material with a 5% cement content.
The site has its own mixing plant for washing, grading and recycling excavated material.
'Nearly all the base material is recycled, although we have a short section of imported fill on a 300m stretch of the M50, ' says Morollon. 'On the R3 project we are also using imported fill for 5km running across chalk.'
Some 600,000m3 of mixed material will be placed, mainly using ABG Titan road surfacers and compacted with vibrating rollers.
The road structure above is in asphalt, supplied from three on site batching plants, which produce 260t an hour. The site also has a concrete batching plant.
There are 100mm thick base and intermediate layers and a 60mm top layer. A discontinuous, negative texture wearing course is being used for quiet running and improved surface drainage, says Morollon. Asphalting is now well under way on many of the stretches and the re-scheduled finish date for the end of this year should be achieved, assuming there is no more rain.
The Radiales scheme has been let under a series of privately funded, 50 year concessions.
Finance will be recovered by tolls.
Each of the four radial roads extends for about 30km from greater Madrid's rapidly expanding perimeter towards the M40 ring road, intersecting the M45 and M50 rings on the way. The dual two lane roads parallel existing but highly congested national roads and will offer an alternative to rush hour and weekend exodus traffic. Every radial road has two toll plazas and three entry and exit points, hard shoulders on both offside and nearside edges, and very wide central reservations allowing space for future carriageway widening.
The concessionaires are also building sections of the dual three lane M50 outer ring motorway, which will be untolled.
For the R3 and the linked M50 and R5 sections the concessionaire is a group comprising the construction consortium plus two road operating companies Autopistas Concessionaria Españ;ola and Empresa Nacional de Autopistas, and the bank Caja Madrid. Ultimate client is the infrastructure and roads section of the Ministerio de Fomento - the ministry of works.
Design work has been by a group of consultants led by Spanish firm Prointec and including Ayesa, Inocsa, Vigiconsult and Incoydesa.