King’s Cross tunnels & canal aqueduct #3

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The final part of the King’s Cross station remodelling took place between Easter and early June 2021 with the west side of the station being closed and the tracks and platforms upgraded to longer sections as well as better track geometry. Unfortunately the design has left the former platform 10 without any track of any sort rather than the platform itself being widened or anything. A result of this is platform 11 is now the new 10. In terms of the canal aqueduct most of the work there involved restoring the eastern Gasworks tunnel, which was finished and in use by late April 2021 with the renewed station platforms (0 to 7) coming into use.

Even though the articles do not specifically concentrate on the remodelling work (eg detailed stuff, technical, etc) but its rather a look at the progress of that and also show the little known King’s Cross canal aqueduct which passes over the East Coast Main Line – and which has been a huge headache for the railway ever since King’s Cross station was opened in 1852! These posts ended up in three parts because of the sheer amount of alterations/developments that affected the railway at King’s Cross. Thus this is the third instalment, and the other two are here (1st) and here (2nd.)

The Gasworks tunnels and aqueduct during the latter part of the #KingsUncrossed upgrade works 2021

In the first picture shown below it can be seen how the railway company had to deal with the Regent’s Canal. The Midland Railway was very fortunate in their choice of land for a new station at St. Pancras next door, whereas the Great Northern had to make do with the bit of land south of the Regent’s Canal for their new station!

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Aerial view of the works 25 February 2021. King’s Cross signal box is evident on the eastern side of the tracks. The alignment of the Regent’s Canal is evident and shows the aqueduct is angled across the three Gasworks tunnels. Source: Twitter

In a nutshell there has really been no easy answer to the problem of how to improve the King’s Cross station approaches,. The 1970s remodelling did sort of address some of the those but added new ones that were difficult to tackle especially switches (points) awkwardly sited on the steepest sections of the layout. Its only because of the advent of modern traction that the trains have been able to manage the station approaches better, and of course the initial Great Northern suburban electrification improved things far more. The total electrification of the East Coast Main Line has too upped the ante somewhat.

However the recent huge increases in passengers on our railways (disregarding COVID) meant a new layout was urgently required. The latest remodelling does give a better track layout, greater capacity as well as extended platforms. In terms of further expansion, that will be very difficult to achieve because everything possible has been squeezed out of the site and should any further improvements be needed, well its going to be very unlikely that railway engineers can squeeze much more out of the layout, apart from say lowering the tunnels. Is it worth it? Not really since this is the approach to a railway terminus and trains invariably are going to be running at quite slow speeds, thus this current layout could well be how the situation exists for the next few decades.

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Gasworks tunnel in November 2020 with the first track ready to be laid. New track being laid in Gasworks tunnel – with the Regent’s Canal’s aqueduct shown up very well in the picture! Notice how the sections of tunnel are built differently around the aqueduct. The canal aqueduct can clearly be seen. Source: Twitter

In regards to these pictures one can discern which tunnels they are looking at simply by decree of the amount of gradient down from King’s Cross as well as the construction of the aqueduct itself. The westernmost tunnel has the aqueduct sited nearest to King’s Cross station, yet the length of aqueduct that’s present in that tunnel is shorter than that in the middle Gasworks tunnel. In comparison the middle tunnel has the longest length of aqueduct that can be seen above the tracks, and this means despite the similarities in construction of the aqueduct, one can discern which tunnel they are looking at. Both of these use what appears to be a base plate sprung from cast iron footings along the top of the tunnel, however unlike the eastern bore, the western bores are curved almost to the base of the aqueduct itself, thus a lengthwise base formed of stone has had to be used to provide strength and stability for the cast iron structure.

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The western Gasworks tunnel with the canal aqueduct quite evident on the weekend of 14/15 November 2020. This is a great picture because it shows the extremely limited amount of headroom underneath the Regent’s Canal! Source: Twitter

One wonders why Network Rail were not forced to do the same here as at Intersection Bridge in Cardiff where the close presence of a metal structure forced them to use electric resistant paint. Maybe cast iron is different? Maybe the tolerances at King’s Cross are actually greater than those at Cardiff? Who knows.

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That darned canal aqueduct again! Seen on 21st November 2020 as the final sections of track were being laid in the eastern Gasworks tunnel. Source: Twitter

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The first locomotives came through the renewed eastern Gasworks tunnel at the beginning of March 2021. Source: Twitter

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OHLE brackets installed beneath the Regent’s Canal. A great pic showing how the aqueduct passes through the railway tunnels. Source: Twitter

Its clear from this image that the OHLE technology has developed to an extent such that the very tight spaces seen here are able to be better utilised and the cantenary wires placed much closer to the top of the tunnel than previously was possible. It must be said the need for OHLE to pass under even tighter structures (such as Steventon bridge on the GWR) has enabled this work through the Eastern Gasworks Tunnels to take place because this is the shallowest graded of the three King’s Cross tunnels.

One would wonder why contact rail as not used in place of cantenary wire? After all contact rail is in considerable use at the nearby Thameslink tunnels – and these have more headroom than there is here. The only reason I can think of is that wire is easier to install and replace than contact rail in such a tight situation but also there’s the canal above and these three Gasworks tunnels can sort of be classed as wet tunnels which means contact rail would present more far problems than cantenary wire. Certainly Network Rail’s own experiences in trying to install fixed contact rail OHLE through the very wet Severn tunnel must have had some bearing on what to use within the King’s Cross tunnels.

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Another view again showing the canal aqueduct – with slab track also seen to good effect. Of course the OHLE is unusual, its a new type for very low locations such as this. Source: Twitter

The middle bore was the first to be built with the western and eastern bores coming later. The canal aqueduct across the middle bore has a flat profile compared to the other two which have a curved profile and this can be seen in the image I have enhanced below. Its also easy to discern which tunnel is being viewed because the eastern bore has new slab track, the middle has traditional track plus a flat bottomed aqueduct and the western traditional track plus a curved structure aqueduct.

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This picture of the middle bore is most fascinating because it shows how low the bottom of the aqueduct is in relation to the railway – and how much the tracks have to dip in order to pass underneath the canal. Source: Twitter

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The Regent’s Canal aqueduct shows its cast iron sides once again as a new OHLE system is installed in the middle Gasworks tunnel. Notice how much headroom is available before the aqueduct itself and then its very restricted headroom underneath the canal itself. Source: Twitter

One might notice the difference in the type of OHLE brackets in the tunnels, such as that above (middle tunnel) and below (eastern tunnel.) The reason for this is possibly due to the fact the eastern bore has a larger profile which means the brackets can sit further back – but also the other problem then is the curved base of the aqueduct so the brackets in fact cant’ sit too close to the walls. The opposite occurs in the middle bore where the bottom of the aqueduct is flat – and even though the tunnel’s profile is somewhat narrower it nevertheless means these smaller right angled brackets can be used.

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Interesting picture showing how the canal aqueduct and the tunnel’s brick lining interface each other. I know its not brilliant but one can at least see the sections are different. The section of tunnel underneath the canal is built in the shape of a ‘U’ and the foundations for the aqueduct itself are laid along the top of this flat top section. Source: Twitter

What that means is the spans that form the base of the aqueduct are sprung from a cast iron base built lengthwise on top of a stone lintel placed lengthwise along the top ‘U’ section of tunnel. This is in the eastern Gasworks bore however. The methods of construction are somewhat different the other two tunnels, especially in the western bore which was the last to be built.

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The eastern Gasworks tunnel ready to accept its first passenger trains after 44 years – but what they didn’t say was the easternmost of the three King’s Cross canal aqueducts would also be seeing the first trains underneath the structure in in 44 years!! The aqueduct is shown to good effect in this picture. Source: Twitter

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The first passenger trains in the eastern tunnel on 26 April 2021 perform a synchronised entry into the station. Source: Twitter

If one looks at the following picture I took of the King’s Cross works just after work on the east side had been completed, its possible to see how the new track layout has enabled the engineers to achieve a shallower approach to the eastern tunnel. This was in fact made possible in part by the rebuilding of the Camden sewer which runs underneath the tracks but also a re-grading of the tracks as they enter the tunnels. The sewer formerly ran at an angle which meant the gradients into the tunnels were even worse then. By moving the sewer southwards and then taking it at right angles beneath the tracks, that at least enabled the civil engineers to move the start of the gradients into the tunnels further back and that in turn enabled these to be eased considerably.

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As my picture shows, one result of the upgrade works is the middle and western tunnels now have slightly easier gradients. The crossover between tracks B and C is on a slight gradient too. What the engineers have done (besides moving the Camden sewer) is to squeeze more out of the available space south of the canal aqueduct. This in part was achieved by moving some of the switches to the northern end of the tunnels. The end result is there’s far more plain track into King’s Cross than ever before. Besides the gradients, one will notice the speed differentials between the western, middle and eastern tunnels. The latter has a speed of only 45mph and that is because the tracks at the other end of the tunnel are essentially a dead end as tracks A and B switch to tracks C, D, E and F, these being the main tracks towards Finsbury Park.

Some may wonder why the tracks didn’t continue further north. Its possible to do this however the Copehagen tunnels also present other problems which means the effectiveness of extending the tracks further north (in terms of cost and engineering and saving transit times) would have been quite small, in other word not good in terms of cost or the benefits it would have offered.

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I love this view looking towards The Cross! The reason for showing this particular view is to demonstrate how much wider the eastern bore is than the others. Source: Twitter

No surprise that they were even able to fit a platform (of limited proportions naturally) quite a few feet into the tunnel itself on the left hand side! By this I’m referring to the fact the platform at the former York Way station was so short they built an extension into the tunnel itself and this wooden platform can be seen on some old photographs of the station. Anyway what is also of importance here is even though there is a new and improved track layout, its interesting to see how these tracks are still graded downward from the platforms into the eastern Gasworks tunnel.

Once the eastern side of the station had been remodelled the work moved over to the western side so we look at these pictures next.

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This photograph shows the western tunnel still has a considerable incline even though the railway is being upgraded. Again its the canal that is the cause of this! Source: Twitter

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Pic looking from the aqueduct to the portal of the western Gasworks tunnel on 11th May 2021. Source: Twitter

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I couldn’t find a picture showing the steepness of the new track into the western tunnel, however the former track’s steepness as it descends into the tunnel is very obvious – an excellent illustration of the gradients needed to pass trains beneath the canal. The new track here isn’t so different. Source: Twitter

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That’s it folks! King’s uncrossed! Source: Twitter

Just to recap, the Regent’s Canal passes across the three tunnels at King’s Cross quite differently because its at an angle compared to the running lines. The aqueduct is nearest to the portal of the western tunnel and at its furthest away from the east tunnel’s portal. The distances from tunnel to the aqueduct are approximately as follows:

Western tunnel: Total distance: 19.23 m (63.08 ft)

Middle tunnel: Total distance: 23.40 m (76.76 ft)

Eastern tunnel: Total distance: 30.34 m (99.53 ft)

Even though the new layout reduces the gradients somewhat and to all purposes and intents that into the eastern tunnel looks absolutely level compared to its previous use prior to 1977, it isnt even level to any extent. Each of the three tunnel approaches still have a certain amount of gradient, with the eastern having the shallowest and the wester the steepest gradients. To help improve the situation the pointwork is now sited well away from the steeper parts of the gradients, and the reconstruction of he Camden sewer has enabled slightly longer gradients towards the tunnels themselves.

The upgrade at King’s Cross offers faster speeds and extra capacity will no doubt help at times to improve reliability along the East Coast Main line. But not always! Recent issues on the ECML saw trains being held as far back as Grantham, Newark and Doncaster because King’s Cross simply couldn’t manage the massive backlog of trains that had suddenly been rained upon it.

Ultimately what it means is the new system is finite in terms of capacity. It can handle extra traffic and unexpected delays. But events involving a dewired train at Ranskill (between Retford and Doncaster) on the 9th November 2021 showed the new system has its fallibility. There was no way the additional capacity could simply accommodate the sheer number of trains wishing to enter King’s Cross station. The result was some trains didn’t arrive in the capital until almost 3am!

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