East Kent is undergoing an £87M regeneration, with a new road paramount to the area’s revival.
Andrea Klettner looks at the vital new transport link breathing life into the county.
East Kent is somewhat of a forgotten area. Where once the seaside towns were bustling with tourists and its beaches were full of day-trippers, it has now become a shadow of its former self.
In 1996 one of the biggest employers in the area, the Richborough Power Station near Sandwich, closed its doors for the last time and now some might say the only draw is the jobs brought by the pharmaceutical giant Pfizer’s European headquarters for research and development, which employs 3,600 people.
Luckily that’s not the local authority’s view and, despite numerous challenges, Kent Council Council is well into the last phase of its £87M East Kent Access project aimed at regenerating the area by improving transport links.
“Building under a live high-speed rail line without disruption to services or lengthening journey times was a job requirement”
The majority of the funding came from the Department for Transport (DfT), with the council stumping up the rest. Geoff Cripps, project manager for Kent Highway Services, says getting the work done on budget is imperative, as any extra funds needed “certainly won’t be coming from the DfT”.
“For us the main aim of the project, which is the last phase of the A299 Thanet Way and A256 that were started in the 1980s, is to improve the economic performance of the area by connecting the ports of Dover and Ramsgate with Kent International Airport,” he says.
But for the engineers involved it was a chance to work on a sizeable road project that demands cheeky solutions to make it a success.
Mick O’Hare, project manager for the joint venture team VolkerFitzpatrick/Hochtief, says: “First we chose a route that doesn’t need any demolition of residential properties. But it does go over and under rail lines used by South Eastern Trains domestic services.”
The two-span composite reinforced concrete bridge over the railway line at Cottington Road is a standard in road construction, but building the tunnel under the live high-speed line without causing disruption to the services or lengthening their journey times was a requirement of the job.
“The introduction of the new Javelin services increased traffic on the line and has made Network Rail even more sensitive to disruptions, they don’t want there to be any problems,” adds O’Hare.
The new road comes at a sharp angle to the railway and within 15m of residential properties.
Preparatory works for the tunnel, which will sit 8m below the track, are underway.
Tony Heron, deputy project manager for VolkerFitzpatrick/Hochtief, says: “We are working on either side of the tracks at the moment installing continuous bored pile retaining walls up to 28m deep.”
There are 100 sheet piles on the east side and 80 on the west side, forming the sides of the tunnel entrances. Once the piling is complete work will start on the area between the piles, which will be excavated to a level of 10m below the tracks.
“Getting the work done on budget is imperative, as any extra funds needed certainly won’t be coming from the DfT”
Geoff Cripps, Kent Highways Services
The excavation is dependent on the chalk season, as set out by the Highways Agency, which means work can only take place between April and October.
“The chalky earth is so susceptible to moisture,” explains Heron. “Out of season it becomes too wet to work with - it can’t be dried out practically - so we’re getting that all done now.
“Once that’s finished we will drive the 3.05m diameter tunnels on the far ends of the final tunnel width, which are 125m long each and sit 9m beneath the tracks, from west to east using an earth pressure balancetunnelling machine,” explains Heron.
“Once the tunnels are in place we will use mini-piling rigs to drive a series of 500, 450mm diameter reinforced bored cast in-situ piles up to 17m deep through the chalk earth. We’re on schedule to start this in January and will finish in March.”
After the piles are complete the team will pour an L-shaped reinforced concrete abutment inside the tunnels, which will eventually go on to form part of the final road tunnel structure.
Ready for jacking
The area below the tracks is now ready for the main tunnel sections, which are cast on site and will be jacked into place sequentially, eventually forming the road tunnel.
“Each section is 25m wide, 20m long and contains 10,000m2 of conventional reinforced concrete” explains Heron. “The first section will act as the tunnelling shield with a steel cutting edge on the front.”
The sections will be jacked forward at a rate of 1m every 12-hour shift and work will be ongoing 24/7 for 10 weeks starting in June 2011.
The East Kent Road Access project has made it into prime time BBC in recent weeks, with archaeological enthusiasts watching the country’s largest dig on the show Digging for Britain.
The eight month-long survey was a key requirement from Kent County Council, resulting in a 6km dig involving more than 130 archaeologists at peak.
Twelve Bronze Age monuments (round barrows) have been found on the project, the largest monument is around 40m in diameter.
Other finds include Iron Age enclosures and a Roman-era village at Ebbsfleet, as well as other Roman settlements, their fields and trackways, Roman and Saxon cemeteries and a large Saxon enclosure.
The team is currently 10 months into the project with archaeological clearance and has even employed special guards to ensure the unearthed finds are protected.
“There will be 7,000t of jacking force in total,” says Heron. “When a section has been pushed 20m, we will remove the jacks add another concrete section and start again.”
As each jack can only push one concrete section, intermediary jacks will be installed between the more advanced units. Each is fitted with a metal joint detail and will eventually be closed and sealed. As digging progresses, the smaller side tunnels will be dismantled, leaving the L-shaped reinforced concrete to form the final resting place for the main tunnel sections.
Eventually the tunnel sides will get a new concrete face and the piles leading up to the tunnel will be covered in architectural blockwork, completing this section of the road.
Work on the entire project is due to finish in March 2012, opening up new transport links for south-east Kent and hopefully spearheading wider regeneration in the area.
Client: Kent County Council
Project manager: Jacobs
Jacking consulatant: Jacked Structures Group
Tunnelling subcontractor: Murphys
Construction value: £87M
Job award date: August 2009
Form of contract: NEC 3 Option A