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Not far outdoors London, two railway viaducts are being constructed for the HS2 railway, which is able to cross by means of one of many extra congested patches of the Chiltern Hills.
The railway passes alongside a protracted pure valley that runs by means of the Chiltern Hills, a legacy of the final Ice Age when glaciers carved a path by means of the hills. As a really handy route for people to get by means of the hills, it’s lined with cities, roads, and railways, making it an advanced space to suit one other railway into.
Many elderly roads want new bridges, and huge numbers of sewers, energy cables, and related infrastructure laid down over the previous century and now inconveniently in the way in which have to be diverted to create space earlier than the brand new railway may be constructed.
Whereas disruptive for native residents and causes prices and delays for HS2, one of many legacies of constructing a brand new railway can be quite a lot of new highway bridges and utilities. Previous slim brick bridges are changed with huge fashionable bridges, and new utility tunnels are typically extra dependable than the previous infrastructure they’re changing.
In some locations, the railway will cross by means of cuttings, however in others, it must cross over valleys on bridges and viaducts. Two of the bigger ones may be discovered close to Wendover, the place the Wendover Dean and the Little Dean viaducts are at the moment being constructed.
Wendover Dean viaduct spans a protracted valley over farmland, however the Little Dean viaduct has to hold HS2 trains over the very busy A413 most important highway and the prevailing Chiltern Railways traces, whereas additionally slipping across the electrical energy energy traces that dot the panorama.
It’s a really congested and busy space.
The principle highway additionally runs very near the railway, making it a troublesome website to construct in, and one the place they needed to transfer the principle highway to at least one aspect to permit house for one of many piers that can help the viaduct.
The undulating panorama additionally introduced a problem with the timing of constructing works. It’s handy that in some locations, they wish to dig down a bit to create a stage railway, and in others, they should fill a small hole with soil so soil from a chopping may be reused domestically. That’s ultimate for lowering waste being eliminated, but it surely means quite a lot of cautious planning to make sure that cuttings are dug down at simply the appropriate time for the spoil to be wanted elsewhere.
And the British climate does take pleasure in messing round with fastidiously deliberate timetables.
Not too long ago, the bigger Wendover Dean Viaduct was structurally accomplished when a protracted streel construction was pushed over the valley, lining up with a row of tall concrete piers. They nonetheless have to solid the railway slab on prime and canopy it with extra ornamental cladding to scale back its visible influence, however after a number of years of labor, the core construction is full.
The viaducts are being constructed by HS2’s most important works contractor, EKFB—a staff made up of Eiffage, Kier, Ferrovial Development, and BAM Nuttall. Specialists at Eiffage Steel are main the manufacture and set up of the beams.
Simply down the highway, although, is arguably a extra fascinating viaduct, at Little Dean. Whereas bodily smaller, it’s really barely heavier as a result of have to span a really completely different panorama.
Whereas the Wendover Dean is passing over what was and can once more be distant countryside, the Little Dean will cross proper over one of the congested patches of land within the space — with the busy A413 and the Chiltern Railway tracks beneath and the electrical energy pylons above.
Over the previous few years, contractors have been diverting utilities and even the principle highway itself to create house for the piers supporting the HS2 railway, which at the moment are being put in on website.
The piers are fascinating.
Usually, a pier could be constructed by assembling a metal rebar cage on website, masking it with a short lived cladding field, pouring concrete into the field, and eradicating the defend to disclose the pier.
Due to the positioning’s constraints, they needed to do one thing completely different.
The concrete “skins” are delivered from a manufacturing unit in Northern Eire as precast segments which might be assembled on-site, leaving an empty shell to be crammed in. They then have rebar cages assembled in Kent and delivered to the positioning, that are then dropped into the concrete shells. This can be a fiddly process made tougher by the lack to see contained in the concrete shell when lining up the joins between the completely different elements.
Having lastly completed that, they’d normally pour concrete into the construction and push vibrators down into the moist concrete to shake it in order that it crammed all of the gaps and removed air bubbles. That’s not doable right here as a result of the metal cages wanted to be so robust that there was not sufficient house for the vibrator to suit, so that they developed a self-compacting concrete combine particularly for this job.
Whereas the piers are being assembled, the viaduct bridge can be being assembled close by in order that it is going to be prepared to slip over the valley subsequent yr.
That work has been underway for a while, and the contractors at the moment are placing the ending touches to an enormous 450 metre lengthy viaduct construction, including the strengthening fins to the edges of the lengthy metal field, whereas the piers are being constructed to help it.
The lengthy metal construction was constructed from segments delivered from France and are so massive that there was simply a few inches of hole to get them off the ferry that delivered them to the UK. They had been then delivered to Wendover by lengthy load lorries in a single day and assembled on website.
Subsequent yr, one of many of the extra dramatic moments within the venture will happen.
Over a protracted weekend early subsequent yr, the highway and railway will have to be closed so the viaduct construction may be slowly pulled over the valley. They’ve to shut the highway and railway for security, not due to the danger of issues falling down, however as a result of drivers distracted by the sight of a shifting bridge might crash their automobiles.
It’s additionally barely difficult by the truth that the viaduct isn’t completely straight however curves and twists barely, so they need to be certain that as they pull the metal over the valley, it traces up completely with the curving line of viaduct piers.
There’s an choice to do the work over Easter, however they hope to do it sooner in order that the closures don’t have an effect on Easter travellers. So, perhaps on Monday morning in February or March subsequent yr, motorists will see a big railway bridge sitting over a highway the place the place there hadn’t been something the earlier week.
As one of many venture managers noticed on the way in which again from the positioning go to, it’s most likely the one time in his profession that he’ll have the ability to construct one thing as huge as this and see it transfer.
That’s for subsequent yr although.
When the builders have packed up and the panorama restored, what’s going to stay are the HS2 railway viaducts, a newly relaid most important highway, and a big part of the Misbourne Greenway. This can be a new strolling and biking route that’s being in-built phases between Wendover and Uxbridge and can make biking alongside the busy A413 doable for the primary time, and HS2’s work outdoors Wendover is delivering this part of the cycleway.
Later, when HS2 opens and takes intercity site visitors between London and Birmingham away from the prevailing railways — that can create the capability for Chiltern Railways to have a look at rising the variety of trains utilizing the Wendover route, so in any case the development disruption, native residents can stay up for having extra seats on extra trains.
The Wendover Dean viaduct seen from a passing Chiltern Railways practice
This text was printed on ianVisits
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