A former High Speed 2 (HS2) area manager has pinpointed two major challenges facing route designers working on the southern half of the project.
Former HS2 Ltd area manager for country north Lee Fisher identified a junction just north of Birmingham Interchange Station and a section of the line in Lichfield as two of the trickiest challenges in the design process.
This is despite the fact that Phase one of the route connecting London and Birmingham consists of seven bored tunnels totalling 41km in length, five green tunnels totalling 7.2km long, seven green portals totalling 1.2km and around 90km of cuttings and embankments and 85 viaducts.
Fisher told a Railway Civil Engineers Association seminar that challenges at Lichfield were exacerbated by a public petition against the initial designs.
Initial designs presented in the hybrid bill, show the line crossing the West Coast Main Line (WCML) and the A38 road. This would have required taking the track over them and would have required embankments 15m high for a length of 10km.
To get the construction materials on site, a large new WCML rail head would have been required. This is opposed by local residents objecting to the size and scale of the impact of construction.
“As we would have gone over the top of [the WCML and A38], some of these embankments would have been 15m high and that provided a technical challenge to design that high while still being capable of carrying a high speed railway,” Fisher added.
“There was a huge amount of pressure, understandably, from the people of Lichfield, who would have otherwise had an unobstructed view of the landscape, to lower the route underneath the WCML.”
In response to the petition, the line was lowered to go underneath the WCML and the A38. Raising the WCML was ruled out due to the amount of time it would have taken to carry out the work. Instead, a solution to jack a reinforced concrete tunnel section underneath the railway during Easter and Christmas is being taken forward.
The Highways Agency (now Highways England) had concerns about taking the line beneath the road with the depths available and clearance needed. Plans to lower the route also ran into public opposition. One local group – which was in the process of restoring a canal – raising concerns that the tunnelled route would put it at the same level as the canal.
“This was an unusual situation of a local group objecting to lowering the route and we had to look very carefully at diverting the canal and moving it around to put the canal underneath the railway,” he said.
The plan to divert the canal was welcomed by the opposition group, but it resulted in pumped drainage having to be installed, something which HS2 Ltd had orginally hoped to avoid as it will require ongoing maintenance.
The second design complexity that Fisher focused on was at Delta Junction in Birmingham.
Delta Junction forms two spurs which branch off the main HS2 line between London and the North (see below). One will be for trains travelling between the Birmingham Curzon street terminus and the North, and the other will be fore trains travelling between Curzon Street and the South. The track arragenement covers a distance of around 10km
Trains will run through the junction in every direction every three minutes and the turnouts (switches) are being designed for speeds of 230km/h.
Delta junction overview
Fisher said that translating this complicated junction onto a real area proved particularly complicated.
“We had to do a lot of work looking at the schematics that would work and that was quite a theoretical exercise because it is constrained in so many different ways and the curvatures of high speed line mean we are quite fixed and what we do,” he said. “This looked complicated, but when we put it into the real world, it took up a lot of space as it is 10km from end-to-end.”
To the south of Delta junction the team had to contend with a major road junction for the M6, M42, M6 toll and the links between them. Fisher said powerlines and a series of gas mains which serve Birmingham also had to be taken into consideration. The route also had to avoide the towns of Coleshill, Water Orton and the Birmingham suburbs.
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