Foundations of Victorian viaducts

[Tony Whittaker]

Dear engineering experts, please may I ask:

I am wondering what the footings of a typical masonry viaduct would look like. Might they be a continuous loadbearing single slab beneath all the arches, particularly if the rock beneath was deemed to be dodgy? Thanks.

 

[Mcr Warrior]

Interesting question! There must be any number of viaducts that were built across the GB rail network in Victorian times, with many still in place, and I daresay that construction methods may well have varied slightly from site to site, depending on local conditions, and who the chief engineer was.

As regards one viaduct in particular, although there are numerous tales that the Ribblehead Viaduct was "built on wool", this is usually now understood to mean that the financing for same essentially came from those who had become rich from the heavy woollen industry of the time.

Believe when the Ribblehead Viaduct was built in c. 1870, the construction gangs had to dig down some 25 feet into the moorland of Batty Moss, i.e. through various layers of peat and clay, until they found solid rock (= limestone) for the foundations of the piers, and then built upwards from there.

Approximately four-fifths of the height of the various viaduct piers are above ground level at Ribblehead, with the other one-fifth is below the ground, but reckon this 'ratio' could well vary significantly at other locations.

 

[Tony Whittaker]

Thanks so much. The reason I ask is that I have been researching the Bugsworth Landslip, which closed the Midland Main Line almost as soon as it was opened. A five-arch viaduct with embankments at each end took the line over a sloping depression in the land. High rain and water ingress into one embankment caused it to slump, and finally take pier and first arch with it. Then about 16 acres of land slid down the valley. However, by all accounts, most of the viaduct seems to have maintained structural integrity and remained standing for 20 years until it was demolished and doubtless its stone used in the base of a new embankment. That seems to suggest that most of the viaduct moved a significant distance as a single unit. I was thinking this would be more possible if there was a single foundational slab connecting all the piers. They must have know the rock strata were dodgy, but not by how much. For shale strata slid over the bed rock, as well as the movement of surface soil. Thanks for any thoughts.

 

[randyrippley]

this page shows a photo of the viaduct during building

Building railways in the 1860s: two Midland extensions | SCRCA

scrca.foscl.org.uk

it doesn't look as if there's a single slab linking the piers

this website about the area

Features of the Black Brook at Bugsworth Canal Basin

has an engraving showing the failed viaduct and the replacement trestle, again no visual suggestion of a single slab

 

[Mcr Warrior]

Wonder to what extend Victorian era construction was essentially 'educated guesswork' by the Chief Engineer in charge of the project, subject, of course, to any overriding budgetary constraints.

Not all that far from Bugsworth, and round about the same time, there was the tragic incident where the Dale Dike Reservoir above Sheffield had disastrously failed in 1864 with significant loss of life.

Believe that Woodhead Reservoir dam wall in Longdendale also had to be partially rebuilt in the 1860s / 1870s after the original was discovered to be leaking.

 

[Tony Whittaker]

this page shows a photo of the viaduct during building

Building railways in the 1860s: two Midland extensions | SCRCA

scrca.foscl.org.uk

it doesn't look as if there's a single slab linking the piers

this website about the area

Features of the Black Brook at Bugsworth Canal Basin

has an engraving showing the failed viaduct and the replacement trestle, again no visual suggestion of a single slab

Thanks so much. Yes, I've got both of those photos. But just wondering if there was some sort of slab beneath ground level. For the reports are that apparently the entire viaduct moved downhill en bloc a signficant number of yards, yet much of it survived until demolition 20 years later. The view of it, with the replacement timber viaduct, shows no visible damage at all, though the newspaper report of the initial incident is that the far embankment went soft, slowly reducing in height, and took out the end pier, with its arch.Then the entire 16 acres of land around the viaduct all moved downhill.

Wonder to what extend Victorian era construction was essentially 'educated guesswork' by the Chief Engineer in charge of the project, subject, of course, to any overriding budgetary constraints.

Not all that far from Bugsworth, and round about the same time, there was the tragic incident where the Dale Dike Reservoir above Sheffield had disastrously failed in 1864 with significant loss of life.

Believe that Woodhead Reservoir dam wall in Longdendale also had to be partially rebuilt in the 1860s / 1870s after the original was discovered to be leaking.

Thanks. I can imagine that was certainly the case. No way of taking rock cores then, I don't think, though there were pile driving available.

 

[randyrippley]

That ground doesn't look like it's been made up after excavation, which is what you'd need if there was a below-ground slab

 

[stuu]

I'm no expert but I don't think viaducts ever have a slab or any connection at ground/foundation level. That's kind of the point!

 

[Tony Whittaker]

That ground doesn't look like it's been made up after excavation, which is what you'd need if there was a below-ground slab

Thanks, that's a very signifant observation and likely rules it out!

 

[The exile]

For the reports are that apparently the entire viaduct moved downhill en bloc a signficant number of yards, yet much of it survived until demolition 20 years later. The view of it, with the replacement timber viaduct, shows no visible damage at all,

I would guess that contemporary reports- particularly if from “eye-witnesses” rather than trained experts need to be taken with several punches of salt. Ok - photos are more believable

 

[Tony Whittaker]

I'm no expert but I don't think viaducts ever have a slab or any connection at ground/foundation level. That's kind of the point!

Thanks!

 

[swt_passenger]

There ought to be historic news reports for the failure. A quick scan of the British Newspaper Archive led me to this somewhat later summary, (Derbyshire Times 5 Feb 1902), within an article giving a history of the line.

I’ve added a screen grab below, but it seems to suggest the original viaduct was curved towards the hillside, and the ground movement caused it to be straightened out, ie the initial movement was not consistent along the length. It says it collapsed eventually.

 

[Tony Whittaker]

I would guess that contemporary reports- particularly if from “eye-witnesses” rather than trained experts need to be taken with several punches of salt. Ok - photos are more believable

One Derby paper gave a very detailed account of the progression of the problem, starting with a track height loss of about a foot. Continual efforts were made to bring the track up to height with ballast as the embankment slumped further until they realised nothing more could be done. The details were obviously from railwaymen onsite, and not just random members of the public.

There ought to be historic news reports for the failure. A quick scan of the British Newspaper Archive led me to this somewhat later summary, (Derbyshire Times 5 Feb 1902), within an article giving a history of the line.

I’ve added a screen grab below, but it seems to suggest the original viaduct was curved towards the hillside, and the ground movement caused it to be straightened out, ie the movement was not consistent along the length. It says it collapsed eventually.

Thanks, yes, I know this one. And, in a sense it did, but not till it was demolished in 1885 Though what state it was in by then is unclear.

Thanks everyone. If you are interested, my write up of the landslip is an appendix to this bigger story is online as an incomplete draft.

 

[Snow1964]

I think they literally dug to something hard and started laying bricks or stone blocks, with next layer overlapping. The quality of the brickwork spreading the load. The mortared mass all interlocking tended to stay together even if whole lot moved.

Most old houses were built same way, dig a trench, lay 4 or 5 rows of bricks, build up about 2 or 3 rows, then step in about quarter brick each side, by time just below ground level would be 2 bricks wide

From what I remember reading in old book, viaduct piers were similar, except after few rows would step in from middle, tapering up towards a square wall ring, with middle often left hollow or filled with rubble. Some used a sort of stone rubble concrete foundation, but I think it depended on the hardness of the ground and the masons who built it

From memory Viaducts were generally built with one of these wide piers every 5 or 6 spans so if there was a problem, only that part would need work.

There was a viaduct (which I think was on Lyme Regis branch line) that had a sunken pier and strengthening arches.

 

[AndrewP]

Definitely wouldn't be a single slab - simply not practical.

Almost all would be masonry foundations with the depth being determined by how deep the bedrock or a suitable base and then building up. If this was in water a caisson would be used to provide a dry space to build in. However, there are oddities; the Brooklyn Bridge which used to carry trains, has one tower built on sand and it seems pretty solid!

 

[WatcherZero]

Would depend on the age and build location, when building near the sea or across a river for example they would flatten off an area of protruding bedrock then build directly on it and in fast flowing water they recognised the need for heavy foundation stones extending below the mud to resist erosion undermining them, however across valleys the foundations would be very shallow verging on the non existent (simply remove the topsoil vegetation and then start laying). Proper building footings as we know them today were mainly an early 20th/late 19th century innovation.

 

[Mcr Warrior]

Sankey ('Nine Arches') Viaduct, perhaps the most important structure needed on the Liverpool to Manchester line (via Chat Moss), and which was constructed in the late 1820s, was built on relatively softish and unsuitable ground (= sandy alluvium).

First numerous wooden stakes were sunk some 20 or 30 feet below ground level, to form the piling, on top of which massive sandstone foundation blocks were placed, and then the viaduct's (splayed) support piers, reminiscent of a canal aqueduct, were built on top of them, towering some 60 or 70 feet above ground level.

Apparently, the viaduct, at £45,000, eventually ended up costing some three times the figure that had originally been budgeted for by chief architect George Stephenson.

 

[DustyBin]

I've always presumed they're built on a masonry pad, but constructed from stone or brick as opposed to reinforced concrete, and that in ground with poor load bearing characteristics the pad would continue down to bedrock level and in effect become an end bearing pile. This is only a presumption though so I'd be interested to see any drawings etc.

Wonder to what extend Victorian era construction was essentially 'educated guesswork' by the Chief Engineer in charge of the project, subject, of course, to any overriding budgetary constraints.

Things were often over engineered for this exact reason. What they were able to achieve without computer modelling etc. is mind blowing really, but there was definitely a tendency to err on the side of caution.

I think they literally dug to something hard and started laying bricks or stone blocks, with next layer overlapping. The quality of the brickwork spreading the load. The mortared mass all interlocking tended to stay together even if whole lot moved.

Most old houses were built same way, dig a trench, lay 4 or 5 rows of bricks, build up about 2 or 3 rows, then step in about quarter brick each side, by time just below ground level would be 2 bricks wide

As above, this is basically what I presumed to be the case. As you say it's similar in principle to a strip foundation under a wall.

(Pedantry alert: The correct term for "2 bricks wide" is actually one-brick thick. I thought you may genuinely be interested!).

 

[DelW]

I think that a continuous slab is extremely unlikely. To spread the load effectively, the slab would have to resist large bending moments and shear forces, and to carry those using brickwork (or masonry) would need something similar to an upside-down mirror image of the deck arches.

Brickwork or masonry works principally in compression, so the normal foundation design is to progressively widen the piers at the bottom in both directions, until the plan area is sufficient to reduce the actual ground bearing pressure to a value that the foundation stratum can carry. That's helped by the fact that allowable bearing pressure increases with depth below ground. However, in Victorian times this was largely empirical, as numerical geotechnical analysis methods were only developed during the twentieth century.

 

[Tony Whittaker]

Trying to post the link to the online article. The system doesn't like an url shortener. Here's the direct link

Dove Holes and New Mills rail crashes 1867.pdf

drive.google.com

 

[DustyBin]

I think that a continuous slab is extremely unlikely. To spread the load effectively, the slab would have to resist large bending moments and shear forces, and to carry those using brickwork (or masonry) would need something similar to an upside-down mirror image of the deck arches.

Brickwork or masonry works principally in compression, so the normal foundation design is to progressively widen the piers at the bottom in both directions, until the plan area is sufficient to reduce the actual ground bearing pressure to a value that the foundation stratum can carry. That's helped by the fact that allowable bearing pressure increases with depth below ground. However, in Victorian times this was largely empirical, as numerical geotechnical analysis methods were only developed during the twentieth century.

Agreed, I think we can rule this out.

 

[Ashley Hill]

There was a viaduct (which I think was on Lyme Regis branch line) that had a sunken pier and strengthening arches.

That would be Cannington viaduct.

 

[snowball]

I think that a continuous slab is extremely unlikely.

Especially for crossing a major river or canal!

 

[Senex]

There's interesting coverage of the restoration work at Bugsworth in The Engineer, 15 February 1867 pp.133-4:
"The new line was opened for passenger traffic on Friday, the 1st instant, the works having been inspected a few days previously, for the Board of Trade, by Major Rich, R.E. It should rather be said the work, for the new portion of the line was inspected by Major Rich and passed several months since, but an unexpected slip of a serious nature occurred in a portion of the new line at Bugsworth, near the northern junction, which stopped the goods traffic that had been commenced, and suspended the passenger traffic until now. The slip, which affected the works for the extent of about half a mile, consisted of a stone viaduct and a heavy embankment, and is supposed to have been caused by the weight having been placed upon a treacherous schistose vein, disposed at a rather acute angle, upon a thin layer of sand. The repair of the works as first constructed involved operations of too formidable a nature to be attempted if the opening of the line at an early date was to be considered a paramount object. In the unforeseen emergency Mr. Barlow, the engineer of the company, recommended a temporary deviation , an idea which has been carried out with great vigour and success by the contractors, Messrs . Eckersley and Bayliss, under the direction of Mr. Langley, the resident engineer. The attention of Major Rich in his inspection last week was confined to this portion of the work, which consists mainly of a viaduct, constructed of Baltic timber of very large scantling; the up rights placed at about fourteen feet between centres, and the diagonal ties, longitudinal and lateral, as close together as they can be placed. The materials and the details in the knitting of this very massive, though in no place lofty structure, were closely examined by Major Rich, and three locomotives, closely coupled, were driven along at various speeds, and rested on all parts in turn, to test the deflection , which was found to be almost inappreciable. The contractors are now at work upon the slipped works, which after being thoroughly footed and made good throughout, will be adopted as the permanent road. There is a heavy embankment of about 7000 cubic yards at one end of the temporary deviation, and a rock cutting of about 4000 yards at the other. The viaduct contains 50,000ft. of timber. The substitution of this work, in consequence of the slip, occupied nearly 400 men for about ten weeks."