Delivery of innovative geotechnical solutions on the Highway Agency’s road network is not being stifled by budget cuts, according to Alex Kidd. Claire Symes reports.
With a third of all traffic and two thirds of all lorries using UK trunk roads, you’d expect the task of bringing innovation to managing and maintaining the geotechnical assets on this network to be a challenge given tightened budgets. But Highways Agency (HA) geotechnical team leader Alex Kidd believes the challenge is not only being met, but the managing agent system is helping to trial cutting edge technology.
Kidd believes that although there are very defined procedures and guidelines within the HA, there is still room for innovation. “Although we use the 600 series guidelines, which have a long history from development in the 1960s and 1970s, for earthworks and the approach is fairly conventional, there are actually very few standards for geotechnics,” he says. Kidd says the HA’s door is open to innovation and points to use of electrokinetics for slope stabilisation on the A21 (see GE, February 2012) and the M5, as well as trials of fibre-reinforced soil elsewhere on the network.
The HA manages around 6,000km of earthworks on major roads in the UK, which are valued at £2bn. Despite this high number of items, Kidd estimates that maintenance of these actually only costs £20M to £25M a year. It is estimated that 94% of these structures are considered stable, placing 775km of the network in the category considered to be at risk.
“The oldest of our assets are 50 to 60 years old following de-trunking of some routes in 2000, so we do not have the Victorian infrastructure that the railway network has to maintain,” he says.
“Over the last few years we have gained a good handle on the location and state of our geotechnical assets and the information suggests that there is no evidence that the rate of deterioration is increasing as the structures age. That is not to say that there aren’t areas where we are aware of problems that need to be fixed, but the number of these is not growing and we are prioritising repairs based on safety implications.
“Asset management is maintenance-focused and we use value management procedures to prioritise spending,” he adds. “The ranking system used for this process is quite bureaucratic and could stifle innovation, but the managing agents are very good at bringing their experience from other sectors to the HA and offering alternative solutions.”
One of the recent successes in this area is the construction of the A421 (see box), which Kidd believes demonstrated the skills and benefits that using managing agents can bring to bear on the highways network.
The geotechnical team is split into three regions with a manager for each. Kidd oversees what is nominally called the Midlands region, but it also covers East Anglia. Dave Pattison covers the South, while Richard Shire, who has just taken over from David Gwede, covers the North. Andrew Jukes, based in the Birmingham office, heads up the team.
The HA currently only has six directly employed geotechnical staff, although it was double that at the peak of road building activity in the UK. “When I started at Bedford, in what was then the Department of Transport, we had a team of three geotechnical engineers there,” says Kidd. “The numbers have reduced partly because the workload has slowed but also because more work is put out to contract now.”
“Over the last few years we have gained a good handle on the location and state of our geotechnical assets and the information suggests that there is no evidence that the rate of deterioration is increasing as the structures age.”
Despite the small team, Kidd says that they are all very experienced geotechnical engineers and estimates that between them they have more than 200 years of engineering experience. “We have all worked in the real world and are not time served civil servants,” he adds.
However, geotechnics - or even geology - was not Kidd’s initial career path but when the degree course he originally planned to follow was filled unexpectedly quickly, he took a place at Leicester University to study geology. When he graduated in 1970 he was unsure about which direction he wanted his career to take, so he opted to continue his studies with a master’s degree in marine earth science at University College London.
The combination of his undergraduate and postgraduate degree led him naturally into the field of mud logging - a big growth industry in the early 1970s with the discovery of North Sea oil and the drive to find other oilfields. Hespent six months in the North Sea, Spain and Africa, but soon realised it was not something he wanted to do long term and looked for more interesting opportunities.
“I then joined Westminster Dredging and I hoped I’d get involved with geological surveys but ended up undertaking marine survey work,” he says. “But I worked on some interesting projects on the Clyde and the Thames and learnt how to use a sextant.”
Kidd was made redundant from the role after six months but fortunately the boom of the early 1970s meant that he had the pick of four jobs offered to him within weeks. He opted to join W & C French Construction at Buckhurst Hill - a decision that took him into engineering and highways for the first time.
“My title was engineering geologist and we had a small ground investigation lab and a number of rigs,” he recalls. “The company worked on the construction of the M11 and M23 - there was a lot of major highway work underway at that time.
“It was a real hands-on role that gave me the chance to do everything, although my main role was in site investigation. I did study soil mechanics as part of the first year of my degree - very few people chose that option - and I soon built on my basic knowledge.”
In 1974 Kidd joined the Milton Keynes Development Corporation (MKDC) and spent eight years running the materials laboratory there. “It was a booming time in Milton Keynes and we were undertaking the ground investigations of the area plot by plot ahead of handing over to the developers,” he says. “The philosophy was to provide everything in-house but the ground conditions were not exactly challenging.”
In 1982 Kidd was again made redundant ahead of the MKDC being privatised and sold off but that was not the last he was to see of the labs at Milton Keynes. Kidd joined Cooper MacDonald & Partners in Epsom and spent six years working on a number of highways schemes both in the UK and overseas.
However, when Cooper MacDonald & Partners bought out the old MKDC lab - renamed Mentor Geotechnical Consultants - Kidd found himself back in Milton Keynes, this time managing the operations.
“Some of the same people were there still but the real change was that we could go after work outside of Milton Keynes,” he says.
Three years on and he was ready for a new challenge. “I saw an advert for a role with the Department of Transport (DoT), as it was in those days, and decided to go for it as I fancied working on some big stuff for a change,” he explains.
One of his first projects was working on the widening of the first part of the M25 between junctions 15 and 16. He also got involved in anything in East Anglia: “There was a lot going on at the time.”
This part of the DoT became the Highways Agency in 1995 but, according to Kidd, the job essentially remained the same. “There were a number of restructures but the role itself didn’t change much,” he said.
“Previously all hands-on work was done in the region with policy decided centrally but the move to the agency structure allowed this to be spread out so there was more knowledge sharing.”
Kidd says that there is no such thing as a standard day and, despite being part of a government agency, he is very much his own boss.
“There are two main streams of work for the geotechnical team leaders - major projects, where we provide support and a review service for schemes, and asset management, which is undertaken by the 13 managing agents in the UK with whom we liaise over issues and problems,” he says. “Asset management is our main focus at the moment with limited budgets for major projects.”
Recycled tyres a clever steer for geotechnics
Use of tyre bales as embankment fill on the upgrade of the A421 between Bedford and the M1 is hailed by Highways Agency (HA) geotechnical team leader Alex Kidd as a real example of how geotechnical innovation is being delivered.
More than 25,000 vehicles use the route each day and under the scheme, which opened ahead of schedule in December 2010, the HA invested £200M in upgrading a 13km section to dual carriageway.
But there were a number of geotechnical challenges that to be overcome by designer URS and contractor Balfour Beatty to deliver the scheme.
The main one was at Brogborough, where the bypass and a realigned side road were constrained to cross a former borrow pit that was partially filled with slurry about 50 years ago. This challenge was turned into an opportunity to pioneer a sustainable road building technique.
“A piled load transfer platform was selected for the dual carriageway while for the side road the most feasible solution was the use of lightweight fill. Only incredibly lightweight material could be used, which is often expensive,” says URS associate Ivan Hodgson.
Lightweight expanded clay aggregates were thought to be the only viable option, until the idea of supplementing this with tyre bales made from used vehicle tyres was suggested by David Baker of Balfour Beatty. Not only were the tyres £25/m³ cheaper, the environmental benefits were also substantial as the tyres would otherwise have had to be incinerated - and they could be sourced locally.
Lightweight aggregate was used to form a level platform on top of which a layer of tyre bales was laid down along the 240m stretch. Each bale holds approximately 100 old tyres, two or three tyres wide. These are compressed and tied with wire. The tyre bales have a density of around 500kg/m3 and a stiffness of 80MPa.
Despite the newness of the technology, there is already a standard for using tyre bales in construction. It is called PAS 108 and requires that tyres used in construction must not be split or damaged in any way. This is to ensure that they do not pollute the surrounding ground.
After one layer of tyre bales was laid, the lightweight aggregate was used as fill for voids between the tyres and vibrated to fill any gaps.
Up to six layers were added to build the road embankment to the requisite height near Brogborough Lake. Previous applications of tyre bales to roads in the UK have been limited to a single layer.
Since the bypass will be maintained and operated by Bedfordshire County Council, the HA and project team had to guarantee their buy in.
The bales have a 50-year design life and the HA is confident that the pavement will not require any more maintenance than a conventional road and has offered Bedfordshire County Council a warranty on the design.