Stanway viaduct update

As everyone will be aware, our biggest structure is the Stanway viaduct. Standing app. 41’-0” (12.46M) above road level and with 15 arches, each spanning 41’-3” (12.573M) and large end abutments it has a parapet length of app. 633’ (192.9M). It is built entirely of Staffordshire Blue Engineering bricks and is a very robust structure.

However, at over 115 years of age, it is not immune from deterioration, and has to be examined as part of a 6-year rolling programme, to ensure that it is safe to carry trains. So, in October/November 2018 we had a further detailed examination carried out by specialist consultants. Due to its size it is not an easy one to examine, as you can imagine!! 

 

Stanway viaduct being inspected from ropes.

Inspection of an arch

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Rope anchors for the external examination

 

The Consultants' very detailed report, received on 12.2.2019, ran to 228 pages and listed a vast number of defects (fortunately mostly minor – much hairline cracking, mortar pointing needed, frost damaged and loose and missing bricks and also some “hollow” brickwork), There were also many damp penetration issues, which had exacerbated most of the defects listed.

At that time (Jan/Feb 2019), we had contractors on site constructing the king post ballast retention scheme. This was to stop the ballast migrating away from the trackbed and slipping down the embankments on the 4 corners. In the fourth picture you can see how much higher the trackbed is compared with the embankment below it, which is why there was a problem.

The picture below shows the situation prior to the start of work on the king posts:

This old arrangement eventually failed, leading to the requirement for a new construction with deeper posts:

 

On the LH photo, showing the steel columns, there is a steel bracket near the top. For the benefit of the curious, these were to attach tie rods, running beneath the track which tied the tops of pairs of columns together to stop them spreading under the lateral pressure.

On the RH picture is the job completed. You can see the steep fall of the embankment, and the high ballast bed of the trackbed above it.

Just 3 months later (13.5.2019) the owner of horse in the field below reported that some brickwork had fallen off one of the piers.

Fallen brickwork on Pier 8.

 

 

After assessing the report's findings, we tried to create a programme of repairs. You may have heard that the Severn Valley did a similar, but far more comprehensive scheme to include adding concrete to the arch slopes, and then waterproofing on top of that; to do that on their 7-arch viaduct cost over £1,000,000. To do the same on ours would have cost something like £2.5M!! There was no chance of coming up with that amount, and so we had to try to prioritise things, and concluded that the first thing to do was to improve the deck drainage. This was done by replacing the blocked and contaminated ballast and cleaning out the drainage pits to ensure that the water could escape through the outlet pipes. 

A contract was awarded, and the work was done in Jan/Feb 2020.

 

Waterproofing one of the brick arches, with a central inspection pit.

Back filling with clean ballast.

 

Then, with the Lockdown still in place, there was an opportunity to apply for money from the Government’s Culture Recovery Fund. This was done, and we were fortunate to be awarded just enough to do the repairs on one pier. The work had to be completed by 31^st March, to qualify for the grant. At quite short notice a quotation was obtained, and an order placed. Following an extremely wet few months, the site was a total swamp with millions of horse hoof prints each filled with 2” to 3” of water, but the contractor was prepared to go ahead and laid duckboards to create a path across the field for walking and as a barrow track for materials. From above the field looked like a WW1 battlefield, with all the mud and holes from the horses' hooves.

 

MEWP in use on a pockmarked field.

 

 

 

 

The contractors brought in a crawler mounted MEWP mobile platform, which could cross the land.

 

 

 

 

 

 

 

 

The first task was to cut out the defective brickwork, which was a long and tedious process. Work started on the missing corner (photo earlier) and a lot had to be cut out to get back to sound brickwork (cut-out completed photo below). To give added strength, 6mm diam helical bars were built into the joints, and wrapped around the corner, for added anchorage. The finished result proved to look as good as original.

A couple of awkward spots were on corners where chamfered bricks extended around corners. 

Chamfered corner, as original.

 

A curved, chamfered brick was needed, and these bricks are exceedingly rare. By extreme good fortune, we managed to find all of the bricks needed from our own recovered brick piles, at Winchcombe, including these “specials”. It's quite possible that some of these originated from the ruins of Broadway, gathered from the site in the early days.

Damaged plinth corner.

Corner rebuilt with specials from our stock of reserves.

 

A large part of the work was to replace about 30 loose or frost damaged bricks:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In this picture you can see missing bricks and plant growth.

Pier 8, after corners were cut out

Pier 8, corner repair.

 

The largest part of the work was to cut out and re-new defective pointing. As the money available was limited, we had to restrict what was done, but we could easily have done at least as much again. The photos do not do justice to the amount of work involved. 

Pier 8, pointing and holes to be repaired.

 

Pier 07

 

Pier 8 was marginally the worst pier, but as can be seen on the photo of Pier 07, there is a similar problem to be dealt with. All piers have similar faults, but some are worse than others

 

Pier 03

 
The worst pier we have had to deal with, so far, is 03 (photo above). This was repaired in March 2014

 

                                                                                                                                          

John Balderstone – 6^th April 2021.