Burdale Tunnel

[sproke]

I am fascinated to know the methods used in the late 1840's to construct Burdale Tunnel. Warwick Burton's book does not go into too much detail of the actual mechanics. Starting at the beginning when the engineers arrived at the hillside in the dale of Burdale, what would have been the first phase in the actual construction? Did they use explosives to start the bore and what sort of machinery would have been used to tunnel into the chalk and shale? What was the significance of creating bore holes on tunnel top (apart from the need for ventilation shafts)? Whilst boring through the dale how did they prevent endless collpases considering the ground was so unstable? I would love to have some answers to these questions if any of you experts out there can help. It is interesting to note that the first major roof collapse happened approximately 18 years after the tunnel was closed. This in geological terms is a nano-second and leads one to think that it is very lucky a collapse did not happen when the line was in use, advocated by the thundering vibrations of the trains running through it. If only there had been cameras around when they were building it !

[Ricgough]

I have to say I am also rather curious as to the working conditions and pre-mechanised techniques encountered by the navvies in the mid-19thC.

As far as I am aware there were 7 shafts sunk to the required depth and then they would work out from the bottom of the shaft. 3 were lined out with brick and became vent shafts, the others were back-filled with spoil.

That technique would explain why the internal bore narrows and widens as you go through - they would have dug the shaft and started working out a double track bore from the base before the financial issues struck, linking these headings with a single track bore in order to complete the structure under the tightened fiscal constraints later in the construction.

When working out these headings, techniques used in the mining industry at that time would have stabilized the roof. In parts, where the chalk was stable there would have been little need for anything, in particularly wet areas, and areas where the bore struck loose shale deposits and un-stable strata there would have been a lot of roof supports (props,boards and beams) close together and probably mechanical pumps. If you have the WB book then you will see that bricklayers, navvies AND Miners worked at the tunnel, so it makes sense that these were guys specialized in working in underground environments, rather than railway construction per-se.

I'm sure WB mentions activity at the Burdale Portal early in the construction also. My guess would be that the precise order of the costruction process would be guided by skills available and number of workers. It is a fair bet that the most-accessible jobs would have been started earliest - burdale portal and the sinking of the shafts for instance.

Furthermore, the shafts that were filled with loose rubble would potentially have created vertical water-courses, allowing the mass of rock above to drain directly into the tunnel at specific points. If you look at the pictures of the roof-fall on forgotten relics then the detrious itself looks uncannily uniform - similar sized boulders and loose-chalk that appears to have just spilled through the brickwork, as if dumped. I believe that if we could pin-point the exact location of the back-filled shafts and compare them with the locations of the current collapses they would have a high probability of corresponding.

Filling a shaft with such rubble would create a pressure-point on the tunnel-roof, as the rock above would not be supporting itself as it would if it were a solid mass, and create an easier route for water held in the rock above to drain into the bore.

If you think about it - soak-away drainage trenches in gardens work the same way - dig a trench, fill to the level with gravel and your flower-beds drain into the trench, filling the air-spaces between the pebbles until it soaks away into the earth.... this is the same thing but vertical and on a larger scale.

It may be that the majority if the tunnel is still okay - 50 years of neglect excepted, as the victorians often over-engineered their structures. It could be that the problems related to the collapses are a localised issue caused by this particular method of construction and that a solution has been found in the intervening 1 1/2 centuries.

It would still probably be prohibitively expensive to restore though, even if this was the case.

[sproke]

Interesting. I remember driving a Jeep all the way through the tunnel (having to do a 3 point turn at the end to get back !). This was in the summer of 1976. We noticed at about the 3/4 mile mark that there was a large amount of water cascading in from the roof (and we got very wet as a result). Two years later the first collapse occured, probably at this point. If in fact you are right about the rubble tumbling in from one of the original filled in shafts, then as I said earlier, it is a miracle a collapse did not happen during the working days of the railway considering the vibrations of the trains running through. I think that somewhere on this site there is an audio clip of a driver or fireman recalling that on his trips through the tunnel in the 50's he distinctly remembers the cascading water.
I think that hypothetically it would have been punitive in costs to maintain the tunnel had it been available for the YWR. Reading the chapter on its construction in the WB book, in view of the endless financial problems they had and the seemingly undisciplined navvies, I hazard a guess that a few corners were cut to get it completed.

[AlanL]

What I have never understood is why exactly they filled in the construction shafts rather than using them as ventilation shafts? You'd think the more ventilation the better?

[Ricgough]

In operational days, the resources of the operating companies would have ensured the structure was well maintained. There would have been regular examinations and surveys, so any problem would have been identified and rectified before it became critical. These things dont fail overnight - there would have been bulging and/or cascading to highlight any issue for months or years beforehand. Shame no-one was looking in 1976.

It lasted 20 years beyond this without a major structural failure - though there is speculation elsewhere on the forum that extensive repairs to the tunnel were made in the years immediately preceeding closure.

It would be interesting to know exactly what part the tunnel maintenance issue actually played in the final demise of the line - at a political level. It would seem to be the only major liability on the route, and at that time, there was certainly one set of safety regs for paying passengers, and another entirely for paid and insurable industrial employees.

I'm willing to bet in a jeep it was a 7 or 8 point turn in all truth!

[AndyB]

I took a walk through Sandsend tunnel about 8 months ago, it has three vents (All capped now) and five construction access vents. The weather had been relatively dry for a week or so, but there was still a deluge of water cascading down all of the vents from the sandstone and clay above. The vents of this tunnel appeared to be in reasonable condition, but I would imagine that over time, the flow path of the water will have created voids behind the brickwork and this will have gradually weakened the 'chimney' structure. Photographs taken in the 50's of the North portal of Sandsend tunnel clearly show some distortion of the portal arch stonework caused by land movement, but British Rail must have taken the decision not to carry out any repairs, even though the line was still in operation.
So this begs the question as to when BR had actually taken the decision to cease carrying out maintenance on these tunnels, and as both of these lines were making heavy losses, did this have any impact on the decision?

[AlanL]

Somebody (MikeE I think) related a story of how BR ran trains to repair the tunnel in 1957. This is borne out by the brickwork of the north portal which is in very good condition.Also if you look at the shots of the north portal immediately pre closure the line had clearly been freshly ballasted and had new concrete fence posts.

[Will]

I took a walk through Sandsend tunnel about 8 months ago,

Is it Sandsend's north portal that's collapsed recently, or is that Kettleness? Or am I imagining things?

[AndyB]

Its the north portal of sandsend, and it has lost about 6 feet. The land movement has distorted the strengthening hoops made from rail, and the arch has fallen down. I don't think the collapse is going to progress much further in the short term and its passable with care, but you will need your wellies on and a good head lamp, its really black in there once you get around the curve at the north end!

[menticknap]

On a personal note, you wouldn't catch me going down a tunnel. Im not really boring, its just that I want to see my 41st birthday!
I dont think we ought to be advising people to go down tunnels......