Tunnelling

Peaky 556 · Jul 18 2020 22:34

The tunnel stretch of about 20 feet that I'm building first, has now been tittled and levelled and loads of pegs put in ready for concreting the base tomorrow. I've added a bit of cant, but don't ask how many degrees; it's a bubble width on my sensitive level, and just looks reasonable! The steel rebar is secondhand from broken gravel boards, and has been placed at the edges as you can see. Why? The most severe loading on the concrete is from the side walls of the tunnel, as these transfer weight from the roof and over soil. Weight of the trains down the middle is pretty insignificant. I'm also using a fairly thin concrete thickness of around 2.5" min

and don't want any cracks that develop into steps. None of this is calculated, just a bit of engineering judgement!

Peaky 556 · Jul 20 2020 22:32

The tunnel is coming along nicely. The track bed is around 18" below ground level here, as my aching back testifies!

Doddy · Jul 21 2020 04:21

Nice one Tim!

Will you be adding bracing arches as well

(Grade II listed Chorley Flying Railway Arches saved from demolition in a collaboration between English Heritage and Network Rail.)

Peaky 556 · Jul 21 2020 09:05

Quote from: Doddy on Jul 21 2020 04:21
Nice one Tim!

Will you be adding bracing arches as well

(Grade II listed Chorley Flying Railway Arches saved from demolition in a collaboration between English Heritage and Network Rail.)

In a word, NO!
In this region of the garden the railway must be roofed over to protect it from chemical attack - hen poop!

Peaky 556 · Jul 21 2020 20:51

Here is my first attempt at an inspection hatchway. I spent time today

sourcing the bricks from a friend with surplus building materials, but it's the first time of using "modern" bricks that are full of holes. Quite frankly they seem to consume so much more mortar and are inefficient in use. I'll have to get better at it as I have several more inspection hatches to install.

John Branch · Jul 21 2020 22:32

Don't tell us that the roof goes on before the track goes down?
John

Peaky 556 · Jul 21 2020 23:41

John, if I could crawl comfortably though a 9"x18" passage I might be tempted, but it's a long time since I could, and I was never tempted by pot-holing!

Doddy · Jul 22 2020 04:18

Time for a rescue locomotive like a Class 08 or 09? OR perhaps the Severn Tunnel rescue DMU?

Or perhaps a change to Berne gauge and use a Windhof based Swiss Tunnel Rescue train?

Jon Nazareth · Jul 22 2020 17:37

Tim

How many inspection hatchways are you going to put in?

Jon

Peaky 556 · Jul 22 2020 21:15

Jon,
Hopefully the attached pic will show that I've erected three 'escape towers' so far. There will be four when the full length of tunnel is built, all spaced apart at around 1.5m.

[Sorry that the image has become turned on it's side for no good reason]

cabbage · Jul 24 2020 15:31

Tim, the 4.5m curve rail ruler is available if you need it.

Regards

Ralph

Peaky 556 · Jul 24 2020 22:30

Ralph,
Thanks but I had a feeling the curve template was quite short, like about 18"? Instead I have dug the tunnel to follow some large wooden templates, used the rail bender to produce approximately the right shape in each track panel, then fastened it down keeping the twin tracks spaced at 190mm centrelines and keeping the tracks away from the walls. It's not necessarily a constant radius, more of a pragmatic solution to keep the tracks following the tunnel walls.

Peaky 556 · Jul 24 2020 22:56

This evening the ground above the completed tunnel was reinstated in preparation for a large flock of hens coming tomorrow to stay for the day as a rehoming exercise! It has been hard work but fun working to a tight deadline. For instance I was still laying track today, and to ensure it stays put and doesn't creep around I have used two methods of fixing. The sleepers are first bonded to the concrete with my favourite PU mastic. Secondly every ~500mm I screw the inside end of each sleeper down with a plug into the concrete. The picture shows the red plastic plug and a screw:

The next picture shows the unadorned tunnel interior disappearing off into the gloom, cab view, but still untried by wheeled traffic.

Peaky 556 · Aug 14 2020 21:24

I have found a bit of time in between decorating jobs, mowing, cleaning out hens etc (my dear wife is away and left a long list for me!), so I have turned back to finishing that long tunnel I dug last month. This is the final 11 feet or thereabouts, dug, levelled and pegged ready for pouring concrete. I'm hoping for good weather tomorrow for this! Must remember to add some steel reinforcement...

MikeWilliams · Aug 14 2020 21:59

Is that a dowel I can see poking out of the previous section? Looks like a proper job. And how thick is the slab Tim?

Mike

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