Sports technology - artificial grass
With the advent of artificial pitches in the 1980s grass seemed to have had its day, but new hybrid technology is giving it a new lease of life.
When England beat Calcutta'Cup rivals Scotland at Twickenham earlier this month in the RBS Rugby Six Nations, both teams could be sure that the playing surface was in immaculate condition.
The pitch, maligned over the years, was re-laid last summer but rather than opting for a traditional grass surface, the stadium's owners, the Rugby Football Union, opted for a hybrid pitch. This combines the strength and robustness of an artificial pitch with the pleasing aesthetics and forgiving properties of a grass surface.
In 1970 former England football manager Terry Venables published a novel 'They used to play on grass', which predicted the end of grass as a playing surface, saying that plastic pitches would become the norm.
That forecast fell short of the mark and although artificial pitches are used in some lower league football and rugby stadia, the majority of clubs spurned the plastic offerings. That was until Desso Sports Systems developed Desso Grassmaster, a hybrid pitch concept that has rapidly gained favour among the top football clubs with Wembley Stadium as well as the grounds of Tottenham Hotspur, Arsenal, Manchester City and Liverpool already benefiting from it.
The hybrid system consists of a 100 per cent natural grass surface into which artificial fibres are injected 20cm deep, every 2cm across the pitch. This results in approximately 20 million artificial fibres reinforcing the natural grass.
The ingenuity of the system is found below the surface. The natural grass roots grow around the artificial fibres, anchoring the field. The system offers stability and reinforcement, ensuring a uniform surface in perfect condition at all times. With the protection from the artificial fibres, the natural grass can recover faster.
"The old pitch was the old 1910 allotments, with 4in of fibre-sands on top with five-metre drains," says Keith Kent, head groundsman at Twickenham. "The contractors dug out 18in of soil - 9,000 tonnes in total, and installed undersoil heating and irrigation under the new surface.
"The artificial grass, which makes up just 3 per cent of the surface, stabilises the pitch because the roots wrap around it while bigger sand particles can also be used."
An additional benefit is the excellent drainage. "The pitch draws water at 123mm an hour, so if the England v Poland football game [World Cup qualifier in Poland controversially postponed last year after heavy rainfall] had been here, we would have played," Kent adds.
Rugby playing surface
"Twickenham had some issues with the original playing surface. It had only minor upgrades during the past few years and Keith and his guys had done a fantastic job with what they had to work with," Alex Stead, Desso's UK sale manager, says. "With the added pressure of additional fixtures and the changing climate we have seen they needed additional assistance and a surface that would give them more stability and a better playing surface."
Under the heavy pounding that a pitch suffers from 30 marauding rugby players, durability is a vital attribute. The root system and the fibres are at such a depth that the whole area will be stable, ensuring that there are no divots to mar the surface. "Sometimes a scar might form between the rows of fibres, these are set at 2cm distance all over the field, it is hard to get in between," Stead adds. "A small amount of soil might be taken off the top but no divots. One of the beauties of the system is that it stays flat and stable throughout its lifecycle."
The importance of getting it right has been highlighted by the fiasco at the Aviva Stadium, Dublin, where a high-tech new pitch that was laid two years ago has come in for real criticism.
A key element of the pitch in Ireland, supplied by Sports Turf Research Institute's (STRI), was the inclusion of a fibre elastic system, which is one of the latest developments in pitch root zone technology. The Fibrelastic pitch was the first of its kind in Ireland, and the same technology has produced great results at Newcastle United's St James Park as well as Ibrox, the home of Glasgow Rangers.
But the pitch cut up so badly during a recent Heineken Cup match that it became almost unplayable. Aviva Stadium manager Martin Murphy recently admitted that the pitch was an on-going concern. "If you look at all the rugby games played over the weekend, every pitch stood up - ours didn't," he said. "The problem at this time of year is that there is no natural growth. We have been trying to artificially stimulate growth, but it hasn't worked as we would like. We are relying on STRI to come up with a solution because it is a concern that the pitch is still cutting up for rugby matches."
The most notable difference between the reinforced system adopted in Dublin and the hybrid pitch is that it relies on reinforcement of the soil structure to assist in stabilising the turf and grass roots rather than implants that form part of the pitch. "We do it in a totally unique way by injecting artificial fibres into the surface that form part of the grass," Stead explains. "The competitors mix a substrate, usually a form of fibre, into the soil - so there will be fibres in the soil that the grass will try and root to, but these haven't been so successful."
The birth of artificial turf came in the late 1960s when Monsanto developed AstroTurf for the Houston Astrodome in Texas, US. The advantages were clear: low maintenance and the ability to maximise stadium revenue by either renting out the stadium for private use or hosting events such as music concerts without concern for damage to the playing surface.
In the UK, football teams including QPR, Luton Town, Oldham Athletic and Preston North End went down the artificial pitch route but it proved unpopular. The unforgiving surface led to some serious injuries for players while supporters derided the high, fast bounce. The FA reacted by banning new artificial pitches in 1988 and the last one, at Preston's Deepdale, was ripped up in 1994.
Since then, advances in technology have led to a re-think. However, at the Football League chairman's meeting at the start of the season there was little enthusiasm for a re-introduction.
"The second generation system used by football clubs in the 1980s was originally designed for hockey to provide a stable and quick pitch," Stead adds. "Football piggy-backed on that idea and pitches went in around the country. Clubs such as Luton Town and QPR thought they were groundbreaking but the pitches were never going to be suitable, they were always going to be far too hard for top level football."
The second generation pitch is a short-pile artificial carpet involving the inclusion of some sand. Third generation pitches, which are the norm for sports grounds and leisure centres around the country, are long pile carpet systems filled with a combination of sand, which gives it stability, and SPR rubber granules, which are in-filled within the system to give you some shock absorption and the sensation of real turf.
There has been talk of artificial pitches making a comeback in the Football League but their planned reintroduction was voted against at last year's AGM. However, according to Stead the technology is ready for another chance. "The scenarios from back in the 1980s have cemented a certain classification for artificial turf with a lot of people in football at that time and there are still some of those within the game," Stead says.
"What I will say is that artificial turf has come on a lot since those times. A lot of testing has gone on and FIFA are heavily involved giving their own classification to facilities. It is getting closer all the time." *
INSTALlATION: FIVE STEPS TO A HYBRID PITCH
Reinforcing natural grass with synthetic fibres is a technique patented by Desso Sports Systems.
Step 1 Bespoke pitch design - Put together an installation team (hybrid grass specialist, local grass expert, external advisors and club owner) to define requirements (climate, architecture, use intensity and applications).
Step 2 Prepare the underlayer - Excavate the ground layer and install the drainage system. Lay down the top layer of sand (enriched with compost).
Step 3 Seed the natural grass - Select the grass varieties and seed in consultation with local experts. If necessary, using sod (rather than grass seeds) can be used to accelerate the installation process.
Step 4 Inject synthetic fibres - Computer-driven machines inject 20 million artificial turf fibres 20cm deep into the pitch. One artificial turf fibre every 2cm ' 2cm: the maximum fibre height above the ground is 2cm.
Step 5 Symbiosis between natural grass and artificial turf - Natural roots intertwine with the synthetic fibres and grow deeper anchoring the natural grass to create a level, firm and stable playing field.
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